Tech Talk

Better known as “Ed’s views on engine building”

Note: January 2018 – The contents of this site was lost and has been recreated. Some wording may differ since the last time you visited.

The title tells it all!  My experience comes via “the road of hard knocks”. If I mention something in this write-up it’s because it works for me. You will have to analyze the data and do what YOU think will work best for you. I guess this is my “disclaimer”. Check back occasionally for “Revisions” shown at the end of this write-up. I try to do a complete update at the end of each calendar year. Your feedback will help keep things accurate. There are real experts on the Hemi – Gene Adams for one. Gene’s perspective is definitely worth reading. It can be found by searching the internet – enter: gene adams. It was posted by Dan Miller.

There are very few (if any) running an early hemi in a NHRA class. Therefore, obtaining maximum horsepower is not an issue for racers like you and I that fall in the “other” category. If you want to run in a 7.60 nostalgia class like NE1, you don’t need 1500 hp in a light car.

I have a very conservative setup: 354 (365″) on alcohol, 9:1 compression, 8% underdriven standard helix 6.71, 22 degrees of lead and my old Engle F31 hardface cam with .600 lift. The car weight is 2000 lbs. with Powerglide and 4.56 gears. This combo ran an easy 7.55 @ 175 mph at Bakersfield (elevation = 0).

First we’ll talk about the individual components and then follow-up with engine assembly, tune-up and revisions. If I have omitted anything or you find an error, please let me know. I am posting this information as an aid for those new to a supercharged early hemi. If I can help minimize broken or burned up engine parts, we’ll call this write-up a success. Have fun!

Individual Components


Block selection should be made with the intended use in mind. If you need lots of horsepower a 392 would be the choice over a 331. If you’re putting together a street machine I would use a 331 or 354. They look the same as a 392 at half the cost. If utilizing a supercharger you’ll have more power than you can handle with the smaller engines. Availability in your area also plays a role. If you have access to a certain size complete engine – use it. You can also use a Spitfire poly block. See “Oil Pump” section for modifications required when using a hemi oil pump. I’ve included a picture of the rear of the Poly block for quick ID – this is a 58W 354.

Let me make a comment on the so-called hi-nickel “W” block. I have never seen any difference in longevity when running a “W” block and would not pay a premium to obtain one. One of the “Petty boys” told me all the hemi blocks were hi-nickel so what can I say.

For most street and some drag racing applications a 2-bolt block is fine. My first purchased engine was a supercharged 331 with 2-bolt mains. This ran OK in a light weight dragster but in a 2900 lb. coupe it destroyed pistons and “rattled” the mains on a regular basis. I ran this block for a year and never cracked a cap or the main webbing. An advantage of the 2-bolt setup is not having to worry about water leaking into the pan as sometimes happens with the 3/8” splayed bolts on a 4-bolt setup. I have only seen a couple of blocks where the 3/8” bolts didn’t break through the thin part of the main webbing. Extra care must be taken to seal these areas. Use silicone sealer where the threads break through and Copper Coat or ??? on the 3/8 bolt threads. Another 2-bolt advantage is the elimination of the costly align boring process.  If you are marginal on the requirements to go to a 4-bolt setup you can take a less expensive route. For my second 2-bolt block I milled the tops of the center three caps and made ground steel straps as a form of reinforcement. If a cap were to crack, the steel support would likely keep things together. I never cracked a cap with this setup.

All my engines now have the 4-bolt caps as extra insurance. I do not use a steel front cap and have never had any problem although my fuels have been limited to gasoline, alcohol and 20% nitro. If you’re running a lot of boost, or utilize heavier percentages of nitro as a fuel, you can make a steel front cap as an extra precaution.  I don’t use a 4-bolt front cap as the outer bolts are not in solid material and could weaken the block. For the center three caps, steel or aluminum works OK. Although most caps are steel (or cast), the aluminum caps seem to absorb the shock well as indicated by a reduction in movement between the cap and block. If installing used caps yourself, keep in mind they will need the mating surface machined down to allow material for align boring. This must be done before drilling and tapping the splayed holes in your block. Coordinate with your machine shop for their preference on how much to machine off. If you are going to fill the block, install 4-bolt mains before filling – the filler will dull the drill and tap.

Billet rear main cap – I do not recommend one. I call this a “one time use item”. Here’s why: When you read the installation procedure for USED caps you will note that just a .001 sideways displacement will require facing about .050 off the cap to ensure a full cleanup at the parting line when align boring. When you do this, what happens to the tang for the oil seal? It drops .050 toward the centerline of the crank making the seal ineffective unless all surfaces related to the seal are machined along with the align boring. Problem solved – NO! What about the pan seal? It has also dropped .050. You’ve got a leaker!  But, my personal favorite is: I’ve beat these things to death and never broken a rear cap. So why spend the extra bucks when it’s not necessary? With ARP studs I doubt if you’ll ever have a problem.

Note: If you are considering a complete billet set of main caps (5) give me a call. I have found some dimensional problems with some aftermarket rear main caps.

Installation of new 4-bolt caps:

  1. Clean registration area in block.
  2. Depth mike steps in block for #2, 3, 4 mains (both sides) – record with marker. Should be around .125.
  3. Mill #1 and 5 caps (if originally on block) down .005-.010. I usually stay around .005 or less to maintain a good seal on rear main and pan seals. Check with your machinist – he may want a different amount.
  4. Mill steps in 4-bolt caps to match recorded dimensions from item 2. if required. On #3 cap, be sure to indicate forward or rear cap face to within .001 vertically before machining to insure equal contact on both top and bottom bearing halves.
  5. Install #3  4-bolt cap. Align thrust surface (rear face) with surface on block.
  6. Flat bottom drill through splayed holes to surface of block – I recommend obtaining a 3/8” flat bottom drill and spotfacing the surface of the block before drilling the 5/16 hole. If you do not spotface first, the drill will walk to the outside when it hits the block and make the bolts tight in the caps. It also nibbles away at the 5/16″ ID drill bushing so each hole gets a little worse. Even with the spotface you may have to open the holes in the caps a few thousandths as they are close to the bolt size. The best source for making a flat bottom drill is a good machinist or retired machinist in your area. Most of these guys have the expertise to flat bottom a couple of regular drills for you. Have them add a small corner radius or chamfer to avoid chipping the edge of the flute.
  7. Install 5/16 I.D. bushing – Drill 5/16” holes into water jackets. You will probably need a 6” extension drill or 12” aircraft drill from the hardware store. Carbide or cobalt is best as cast iron is abrasive.
  8. Remove bushing – Tap 3/8”-16 through with extension tap.
  9. Repeat for #2 and 4 caps.

The bores on new caps are undersize – no further preparation required.

Installation of used caps:

Sometimes this is more work than you want to get involved in. You’ll understand after you read the procedure below.

  1. Clean registration area in block.
  2. Depth mike steps in block for #2, 3, 4 mains (both sides) – record with marker.  Should be around .125.
  3. Mill #1 and 5 caps (if originally on block) down .005-.010. I usually stay around .005 or less to maintain a good seal on rear main and pan seals.
  4. Used 4-bolt caps are already bored to the finished size which means there is zero material at the parting line and whatever you machine off vertically whereas new caps have material on all sides. Your assignment, should you decide to accept it, is to ensure there is sufficient material for the machinist to clean up when align boring.  Check the mismatch between the bores in the caps and block at the parting line. This could be determined by carefully measuring the distance from the registration step to the finished bore on both caps and block and then subtracting the difference. You could also install the caps and try to see or feel for a mismatch between the cap bore and the block main bore. If there appears to be little or no mismatch, machine the steps in the caps down about .075 and recheck. The bore in the caps must overhang the bore in the block slightly. The following data is supplied for machining of the mating surface of cap and shows the material that will be provided for align boring (per side): .050 = .001, .075 = .002, .100 = .004. If the caps are shifted to one side or the other by a significant amount, they will need to be machined down accordingly. Let’s say the bore in the cap is overhanging the bore in the block on one side by .006. We’ll use .007 to be safe. Recall your trigonometry? Here’s the calculation for a 354 main bore at 2.562:  2.562/2=1.281 which will be the hypotenuse of a right triangle. The side adjacent will be 1.281 less our .007 or 1.274. We’ll be solving for the side opposite which will be the depth of cut required. Call it “D”. Soooo, D= square root of [1.281 squared (1.64096) minus 1.274 squared (1.62308)] which equals the square root of .001788 or D=.1337. If you remove .134 from the cap it will cleanup when align bored. STOP! If you machine .134 there won’t be any registration surface left. In this example, before removing the .134 take a 1/4″ endmill and drop the registration surface about .150. Stay away from the existing registration surfaces about .0005 (a half thousandth) to make sure the cap is tight. If the cap is loose to begin with, you can leave a little extra here to tighten things up. Once the machining is complete you can face off the .134 and then the steps recorded in 2. above. The 1/4″ cut will enable you to cut the steps without touching the registration surfaces. Re-machine (or file) the groove for the bearing tang to restore original depth. I set the cap on its side and use a keyway cutter to re-machine the groove. If the splayed holes are oversize on the used caps, make an appropriate diameter drill bushing. For example: Say they are 25/64 (.390) – use a 25/64 flat bottom drill to spotface. Make a 25/64 OD x 5/16 ID bushing for the drilling operation. Remove bushing and tap. If a shop is doing your work, have them prep as described. On #3 cap, be sure to indicate forward or rear cap face to within .001 vertically before machining to insure equal contact on both top and bottom bearing halves.
  5. Install #3  4-bolt cap. Align thrust surface (rear face) with surface on block.
  6. Flat bottom drill surface of block – see item #6 above.
  7. Install drill bushing. Drill 5/16″ holes into water jackets.
  8. Remove bushing – Tap 3/8”-16 through.
  9. Repeat for #2 and 4 caps.
  10. Not as easy as one would think. Maybe that $75 you paid for used caps wasn’t such a good investment after all! If a machinist is doing all the work, a new set of caps would be cost effective. Of course if you’re doing the work yourself, you’re working for free so why not.

Cracks – Check block carefully for cracks. If there are any cracks running from the head bolt holes to the water jacket holes or cylinder wall to the water jacket holes and you are running alcohol, don’t use it. Too much cylinder pressure is produced. The block in the picture cracked in this area on #1 cylinder when a sleeve was pressed in. It continued cracking all the way across to #7 and also down the cylinder walls.




There was no detonation going on – just normal operating cylinder pressure. Not visible is a hole in the left cylinder wall providing a route for the flame to pass by the rings and piston skirt – looks like a piston out of a fueler! I have run blocks with small cracks in the areas described where the horsepower output is below 750 with satisfactory results. These were supercharged gas engines. Other areas to check are of course the main webs as well as externally near the deck and about an inch above the pan rail. If you have a welder familiar with cast iron you can have the external cracks repaired. If running water, silicone over the weld to eliminate the possibility of a leak. Once the visual is done, have the block magnafluxed to uncover other gremlins. If available to you, a sonic test is a little extra insurance against core shift.

Sleeves – Do not use standard cast iron sleeves on a high horsepower engine. Go to a sleeve manufacturer like Darton and order ductile iron sleeves with a .187 wall (.125 min). Do not order a step sleeve. There are advantages to a step sleeve, BUT, they also eat into the deck and weaken it. These blocks have pretty thin decks (about 1/2 the thickness of a small block Chevy) and we don’t want those nasty cracks starting. Take another look at the pictures.

Block cleaning – If you are going to run alcohol with a filled block or gasoline with a filled or partially filled block, the inside needs to be clean so the filler will be tight against the cylinder walls. You don’t want .020 of rust or sludge between the block and filler. It’s best to use a process that removes the crud like a Wheelabrate process, ultrasonic, baking, etc. Make sure you remove the oil gallery plug located in front of the oil pump drive gear. The larger plug in the rear of the block is just a cover. If you chase the threads on this plug (or install a different one), make sure you check for interference with the distributor drive gear. If touching, grind some off the end of the plug.

Paint – Just like the old days, I use Rust-oleum Chestnut Brown. The engine stays cleaner and looks nice with an internal paint job. The valley can be partially sprayed and then finished with an artists brush as long as you don’t shoot in the lifter holes. The crankcase side must be completely painted by hand. Plan on spending about 3-hours. Note: If you leave alcohol contaminated oil in the pan for any length of time it may start to degrade the paint.

Block filling – In my supercharged gas engine I ran water in the block and it worked fine – no split walls. With an alcohol engine I would definitely run a filler for additional support and rigidity. When filling the block, level front to back. Install cylinder heads using plastic sheet ( heavy drop cloth material) as a gasket. Fill through the freeze plug holes. Let stand for a week before removing heads. This process fills to the very top of the block. If you try to fill from the deck side it’s too messy to fill all the way to the top. In addition the filler sinks after drying. Copper head gaskets (without water holes) will then sink into the holes from heat making it difficult to reuse them on a different block. I like Moroso filler because it comes in four bottles for mixing.

Head studs – Not a requirement for a street engine since you’re not going to be tearing it apart on a regular basis. Studs will preserve the tapped holes in the block if it’s coming apart often. If you’re going to “crank it up” (alcohol over 10.5:1, lots of boost or nitro) you will want to consider 9/16 studs for added holding force.  Hey! I make a kit for drilling and tapping the existing holes to 9/16″ – Imagine that! Check out my “Products” section. You want these holes perpendicular and centered so don’t try eyeballing for location and perpendicularly. Note: Considering the thin deck, I don’t drill through the cast boss for the head bolts when installing 9/16″ studs. This is just my preference to preserve strength but have no data as to whether it is effective or not.

Boring, decking, etc – SOP machine shop stuff.

Block honing – The pros always use a honing plate. Then again they’re looking for that extra 5 hp with standard rings. On my hemi, the difference in leak down is about 8% more without a honing plate than it is if one is used. Here’s my advice: If available for your bore size, I would use a .017 Dykes chrome stainless or ductile Fire Power top ring from BWE Piston Rings (Bruce Walker). If you do not have access to a honing plate, go without it. Performance wise, there is no difference when using a Dykes ring. In a full throttle situation they will seal with 50% leak-down. IF the Dykes is not available, you will probably need a hardened ductile ring. If this is the case, you will need to use a honing plate as these rings are not as flexible and not constructed to exert the pressure on the wall like a Dykes. The standard hardened ductiles do exert more static pressure but not as much as the Dykes under power. For a street setup both these types of rings are too severe on the cylinder walls and you should go with something like a Total Seal. Not many machine shops have a honing plate for an early hemi. If you’re going to do a lot of racing I would invest in your own plate. BHJ makes a nice one but they’re expensive. Note: The final hone for the Dykes and hardened ductile is 280. I use a 25-35 degree cross hatch. Check with manufacturer for other rings.  Note: BWE can usually custom make dykes rings in the more popular sizes. In some cases they can use a standard ring and cut the Dykes step. BWE can be contacted at 805-985-1008. Tell Bruce that Ed Middlebrook referred you and he will give you the best deal possible. I’ve been buying rings from Bruce since the ’70’s.

O-ring / receiver grooves – Most builders o-ring the heads and put receiver grooves in the block. This method provides a little extra protection for keeping the gasket in place. The receiver grooves only need to be about .010 deep. Deeper just weakens the deck surface. If you’re going to o-ring multiple blocks, invest in an Isky “Groove-O-Matic”. I think I got mine through Competition Products. You can also use the Groove-O-Matic cutting head to cut o-ring grooves in the head. You’ll need to make an adapter to fit one of the cheap (Chinese) single point fly cutters that use a brazed or carbide lathe tool. I’ve seen them on ebay for about $25. I made the adapter shown in the fly cutter. I machined it flat and then heated and bent it to make the o-ring blade perpendicular to the Bridgeport table. The cutter assembly to the left is from the Isky “Groove-O-Matic”. You will need to rotate the grooving cutter super slow so as not to oversize the groove. If you already have o-rings in the block, spray the head white around the combustion chambers and mount the head to block. Add a couple bolts or studs and tighten to about 25 lbs. Remove head and use the impression made by the o-ring to center on mill. This method also works to locate the receiver/o-ring grooves on the block surface.

As noted below, I destroyed my good set of iron heads and had to go with an old set of Webster aluminum heads. The existing receiver groove diameter in the block was not the same as the o-ring diameter in the head. The o-ring groove diameter in the head was about .100 larger than the diameter in the block. Since I had previously experienced “pushing the head gasket out” slightly I decided to deepen the receiver groove in the block to accommodate an o-ring. I used two o-rings and have not experienced any movement of the gasket with this head/block combination. This is not advisable if the two grooves are close to aligning with one another as it would tend to cut the gasket.

Intermediate Shaft Bushing – Check the bushing in the block for wear by using the intermediate shaft as a gauge. These bushings sometimes crack at the seat (not visible) or are damaged during the block cleaning process. To be safe I always install a new one. After breaking a bushing at the track, I now fabricate a removal and installation tool. Check the “Products” drop-down on my website for this handy tool.

Factory oil holes – I have seen the oil drain-back holes as well as those in the mains drilled out. Some of the “old timers” say this helps but I leave mine “stock”. If you’re running a small cubic inch class engine at 10,000+ rpm, oiling may need further consideration. For what we’re doing just leave them alone. Stock holes worked fine for my 9000+ gas motor. I have received a few calls noting they’ve been told the early hemi is not a RPM motor. From my experience the only RPM limitation is the long exhaust rocker arm coupled with extreme cam lift and the spring pressure required to avoid valve float. I’ve never had a “bottom end” oiling problem. If you own a 392 there are some rpm limitations due to the larger journals, piston speed, etc. It’s kind of like the BBC vs SBC comparison.

Oil diverter (bypass) assembly – This is the check ball assembly under the rear main cap. This is usually removed in favor of an aluminum diverter without a check ball. The aluminum diverter just drops in the existing hole and directs ALL oil to an external filter. One negative is that they restrict oil flow by about 20%. The holes in the pump and cap are .500. The hole in the block where the diverter drops in is about .572. Take away the wall thickness on the drop-in aluminum diverter and you restrict the flow down to about .400 where oil exits to the filter. There are three options:  1) Tap the hole and use a plug to block off oil flow between the two holes going to the filter pad. 2) Use the standard aluminum diverter. 3) Buy one of my aluminum high-flow diverters that will flow close to .500 diameter – Additional information and pictures in the “Products” section. It will flow 20 – 50% more than ANY bypass on the market.

If you are running a street setup and want to use the stock oil filter adapter/canister, just clean and re-install the stock bypass assembly.

The stock bypass is in two pieces and sometimes hard to get out due to rust, etc.  If unable to remove using a piece of rod through the oil pressure hole or you intend to reuse the stock bypass, take a hammer and lightly tap an EZ OUT into the hole in the bypass assembly. Twist counterclockwise and lift to remove. Remove ball bearing. The bottom section has a 5/16 hole that can be tapped to 3/8-16. Starting the tap may be a little difficult since the bottom piece of the diverter has two short tangs pointing upward – eventually it will go. Use a 3/8-16 bolt and washer as a puller. Warning: Removal by any method may render the assembly unusable.

Whew!  Did we cover everything? If all this sounds like a lot of work, Gene Adams has a new cast iron block coming out with all the upgrades done for you for about $3000+ – exact date & price TBD. I hear an aluminum block will be next. Anyone have an update?


Hemi cranks are tough. I’ve never had a problem with a prepped stocker and have well over a hundred tough runs on the one in my gas engine. If running on alcohol, I would recommend sending it out every season for a wet magnaflux. If running a supercharger closely inspect the forward fillet radius on #1 journal for cracks. This area takes the most abuse since it’s driving the supercharger. How much horsepower can they take? I’m currently somewhere between 1000 & 1200 hp with 50 runs on the crank. Time will tell as this is my first alcohol engine. If you’re not running nitro, I would try the “stocker” first – billets like a Velasco are expensive ($3000+). Update: At the 2012 March Meet in Bakersfield I noticed the crank trigger pickup was rubbing the degree wheel – #1 rod journal cracked after about 65 runs. Will keep you informed on my next stock crank so we will have a better idea of the “life of a stocker” on alcohol.

Used cranks – If you’re going to run a used crank “as is”, place it between #1 and #5 mains bearings (2, 3 and 4 removed) and check them for run-out. This should be less than .001 (0 – .0005 preferred). If more, have it straightened. It’s also mandatory to have it wet magnafluxed. A note on main bearing runout: A good crank grinder always finish grinds the mains last. Any reworking of the rod journals will likely tweak the mains necessitating a main re-grind. Check all mains for runout. Be sure to check the flywheel flange for runout. This becomes critical if running a clutch and heavy flywheel.

Crank grinding – I am using Castillo’s Crankshaft Specialists to do my work. Prices are reasonable and Joe does good work. You can contact him in the morning at 714-523-0321.  For racing I have Joe turn the rods and mains .002 undersize (.0005-.001 for the street). This yields somewhere around .004 clearance. I also have the crank nitrided and if necessary have the width of the throws widened to provide about .035-.040 clearance between rods. This eliminates having to mill the cheeks of the rods down to provide the clearance. If the clearance exceeds .035-.040 don’t worry as I have seen clearances up to .070. If you want a little extra clearance on the thrust main, this is the time to do it. Shoot for about .010.  A popular practice is to turn the throws down to big block Chevy size to provide for a better selection of bearings. I have been grinding my throws down to small block size to reduce bearing speed as well as availability of bearings.

Grooving and/or cross drilling –I don’t find this necessary and I don’t do it on my new cranks. I have purchased a couple of cranks with this type of prep and they worked OK (low rpm motors) so I can’t give grooving and/or cross drilling a thumbs up or down although there’s plenty of controversy on the subject. For high rpm motors I would not use a cross drilled crankshaft as oil starvation can occur. Oil hole diameters should be ¼” for high rpm applications. Cranks with 3/16” holes are OK for rpm’s below 8000 or for street use. For high rpm, have the holes opened up before nitriding or select another crank. Below is a PDF from Vandervell / Mahle on main bearing groove length. Just something to add confusion but very interesting.

Stroking – If you decide to increase the stroke, it is important to consider the modifications required to the block and/or pan. Excessively long strokes will eat away at the water jackets and pan rail often necessitating an elaborate and expensive pan along with the possibility of an internal water leak.

Install a piston/rod and swing the crank to see where the clearance problems occur – record the readings. Some minor clearancing of the block may be necessary with aluminum rods and a stock stroke crankshaft.

When adding a longer stroke crankshaft you will want to check three areas: 1) Rod beam as it passes the bottom of the cylinder 2) Big end where it passes the bottom of the cylinder and the pan rail 3) Big end rod bolt where it passes the bottom of the cylinder and the pan rail.

When finished with your measurements and trying to decide on a stroke, keep in mind you can go twice the clearance in stroke increase. Let’s say with a stock stroke crank everything clears the pan rail and/or pan by .320. You could increase the stroke up to 1/2″ (1/4+1/4) and still have .070 clearance (.320-.250=.070). When you’re looking at as little as .070 clearance you will need an accurate representation of the rod you’ll be using. You can take a rod of the same length (or my adjustable rod) and build up the corners at the bolts with clay to the width and height of the rod you’ll be using.

Note: The inside of a stock pan measures about .550 from the centerline of the pan bolt. A rod will usually contact the pan before it contacts the pan rail where it steps down. The pan rail step is about .500 inboard from the centerline of the pan bolts.

If you decide to run small block Chevy rod journals you can get a free stroke job (sounds like fun) when Joe grinds the throws. Pickup 20+ cubes without welding due to the smaller Chevy journal size. The downside would be the inability to increase the fillet radius thereby eliminating the stock rolled undercut. The stock fillet can also be welded up to provide for the larger finished fillet but I shy away from any unnecessary welding – just me. Increasing the fillet radius on the rod journals takes away from the maximum increase in stroke. BUT, a larger fillet also adds strength. Try to maintain a minimum of a .090 fillet (.120 preferred) for racing applications. The weak point on the crank is #1 throw since it is the closest throw to driving the supercharger.  A .120 fillet will add significantly to the longevity of the crank. If the crank is to be used for the street, OK to increase the stroke.

If you already have a 331, 354 or 392 stroker rotating assembly, use what you have – don’t spend the extra bucks.

Main bearings –The only prep to consider here is on the thrust surface of the center bearing insert. Using a triangular file, I add three grooves by about 1/16” wide to all thrust faces. This is particularly important if you are running a clutch. When you depress the clutch and hit the throttle, the crank presses against the rear thrust surface and cuts off oil flow. Without the grooves the thrust surface is usually shot after a few runs. OK, If you leave at a low rpm it may be fine. I’m talking about a hard leave. Bearing selection – Unless you can find an old set of Clevite 77 bearings (MS1417) you’ll have to go with the King bearings. Note: For rod bearings see “Rod Bearings” below.

Flywheel Flange – A stocker comes with holes for “through bolts”. If you have a “virgin” you will want to tap these out to 1/2-20. I make a quality tapping block that will ensure the tapped holes are on-center and perpendicular – check out the “Products” section.


Recommendations for compression –

Supercharged gas – street:  8:1

Supercharged gas – strip:   9:1

Supercharged alcohol:        10-12:1  (Over 10:1 the use of 9/16” head bolts is recommended)

Due to the opposing valve reliefs it’s harder to get optimal compression on the smaller displacement engines. The valves basically eat into the dome area with nothing left for “compression”. My 300” class engine has everything in the book done to the dome to try to maintain compression. There are even male tulips on the dome to match the female tulips in the valves and compression still isn’t where it should be.  With a 392 you’re practically at 9:1 with a flat top.

Calculating compression – Except for the big inchers with flat tops, there’s no easy method here. The procedure below assumes an obtainable compression ratio without custom machining the entire dome. It does not cover every detail of the machining as this would take pages.

I fabricate an adjustable connecting rod. There are many uses like trying various “long rod” combination and calculating the compression ratio without having to have the actual rod you will be using. This is well worth the investment. See the Products section.

For a 331 or 354 you will need a piston of the correct bore.

  1. Clay up the valve reliefs on the junker piston and assemble engine with TDC set, camshaft you’re going to use installed and degreed in, head, head gasket and valve train installed with valve lash set. I cut the clay into strips so it is less likely to stick to the valve.
  2. Rotate assembly two rotations to determine valve to piston clearance and disassemble. I run about .150 intake and .190 exhaust although these numbers could be as low as .100/.120 if you’re looking to increase compression. I like more clearance so I can safely advance or retard the cam if necessary. If you don’t have enough clearance, mill the reliefs down and to the correct diameter for your valves. Piston manufacturers usually come off the valve reliefs with a 45 degree cut to provide a little more meat at the top ring land and to un-shroud the valve – try your best to simulate this cut as seen in picture below. Note: Top ring placement should be as close to the top of the piston as possible. For supercharged gas a lot of heat is generated. This distance should be at least .125 from the deepest part of the valve relief.
  3. Assuming your junker piston doesn’t have a huge popup and you want to increase compression, clean the dome thoroughly (shinny aluminum), drill 8-10 1/4″ holes in the dome area, scuff up the remainder with coarse sandpaper and put a masking tape “dam” around the piston. Fill with Bondo except where the valve reliefs are located.
  4. Turn outside diameter on a lathe as well as a 45 degree angle (see side shot) to simulate the curvature of the dome of the head. Keep the 45 degree angle as close to the head as possible – say .050. If you want more compression, or your engine is of a smaller displacement, add a little more to the top later. If displacement is more, take a little off. When you get it looking something like mine (see photos) it’s time to reinstall in the block and go for a cc check. For accurate results you’ll need the long 100 ml lab burette.  Note: 1 ml = 1 cc.
  5. Grind one of your top rings to obtain a 0 -.002 end gap. Use a small amount of Vaseline on all surfaces of the ring and install on piston. After installing piston/rod in engine move about 1″ down the bore. Put a thin film of Vaseline on the bore and move piston to TDC.
  6. Use carpenter’s level to level head surface of block in two directions.
  7. Add head gasket and head – no valve train required. Do not rotate assembly – keep at TDC.
  8. Fill burette with water – I usually use ATF but we don’t want to get the Bondo oily in case we need to add some additional material for a re-check.
  9. Fill the combustion chamber through spark plug hole until it is full. When full, record the cc’s used. Check for water passing by the o-rings and dripping out the bottom. If water is leaking fix the problem and retry. If you can’t stop the leak, use ATF.
  10. Remove head and using a Plexiglas cover with hole, cc the combustion chamber in the head for future reference. Use a little Vaseline to seal the Plexiglas plate. Add clamps if necessary.
  11. Using your readings, utilize an on-line compression calculator to see where you are.
  12. Re-Bondo, rework, re-cc until you get the desired compression. Note: The piston shown in the picture above has intake and exhaust reliefs of the same diameter so piston placement is not important. If additional compression is needed, the exhaust relief can be reduced in size. You might gain 1/4 – 1/2 point in compression.
  13. Send piston to your favorite piston manufacturer. Order 10 pistons and 8 quality pins with aluminum buttons. Price about $1100. Note: Add .001-.0015 extra skirt-to-wall clearance to the manufacturer’s recommendations (usually .007 on a 4-inch bore) if running a filled block. The extra clearance reduces the possibility of piston skirt galling due to the lack of heat dissipation in the block. I know, some say a filled block dissipates heat better. To me, scuffing of the piston skirts says otherwise. You can also opt for a coated skirt to minimize galling – of particular importance on a supercharged gas motor. Be sure to take a little extra off the skirt to compensate for the coating. Check with manufacturer. Another note: Prior to ordering your pistons, place a ¼” diameter punch, rod or drill (upside down) in a vise and touch off the top with a 1” travel indicator. Zero indicator. Slide piston onto the rod or drill and read the thickness through the dome and valve relief areas. You want .250 for a supercharged gas applications – .200 OK for alcohol. With a permanent marker, mark the thickness on the top of the piston at various locations. Once completed you will get a pretty good idea as to where the thin and/or thick areas are. The piston manufacturer can then position the finished piston within the piston “blank” to provide .250. They can also lighten the pistons in the thick areas and add skirt coatings if desired.
  14. Reinstall new piston in block and re-cc. Recalculate to find your alcohol pistons are 9 1/2:1 instead of the desired 10:1. Don’t worry it will still run fine – add some to the dome on your next order. If compression is too high just face some off the top and re-cc. They never come out exact on the first go around. You can also order the domes a little high, cc the assembly and then machine some off to obtain the desired compression.

Here’s a “poor man’s” tip on getting the most out of your pistons. I mentioned going through a lot of pistons when trying to figure out a supercharged gas tune-up. Here’s what I did: 1) If you knock out the top ring land on a piston machined for Dykes rings send them back and have the top ring groove opened up for a standard size ring. 2) If you damage the skirt due to heat (black marks – sometimes called “black death”), mask off the ring grooves and sand blast the skirts. You will remove the black areas and the small peen marks will retain a small amount of oil. So you have just saved $2000 without sacrificing much performance. In the old days I would send the pistons to Arias and have them install brass skirt buttons but I don’t know of anyone doing this today – ask! Skirt buttons stick up above the skirt .001-.002.


I’ve discussed my preferences (.017 chrome stainless or ductile Fire Power Dykes) under the Block section. I use a taper face ductile or standard napier for my second and a standard tension oil set. Here’s a story you might enjoy. I was on a tight schedule to get the engine ready for a race and noticed the chrome on one top .017 ring was burned off due to a lean mixture in that cylinder. At the time I didn’t have any 4″ spares for replacement. A check of my inventory revealed a new set of .017’s for a 392 with a 4.06 bore. I decided to try this ring in my smaller bore. To my surprise the leak-down was the same as the other rings. I ran it this way until the next ring change with no difference in performance. There are a lot of  4.030 and 4.040 392’s around. Although a little unorthodox, if you can’t get a cheap Dykes for these bores I wouldn’t hesitate to try up to 4.060.

End gap – Manufacturer’s recommendations are about .030 for a 4” bore Dykes and ductile top ring. If you grind too much off and end up over .030 don’t go out and buy a new set. I’ve tried as much as .045 with no change in performance – maybe a little more leak-down. A note about ring filers – Buy one with a good wheel like diamond impregnated. I bought a K&D as a spare and the wheel wore out on (4) rings – junk.  Dykes and hardened ductile are tough whereas your second ring is softer – don’t over file the second ring thinking it takes the same number of “cranks” on the ring filer. File one end of the ring only and deburr.

Ring replacement – The Dykes seal so well that you can reuse them as long as they haven’t collapsed or do not have burned areas (brown) on the face. I’ve used the same set in two blocks and over 60+ runs in each. I check the gap when new (not installed) and replace them when they start losing tension (gap gets smaller by about 25%) or I see the change in the leak-down. Supercharged gas is a different story. If lean on the main you’ll notice an increase in leak-down. As noted previously you could be way lean and see 50% leak-down. If in competition, don’t panic, the rings will still seat under power. Richen things up and change the rings when you get home. With 50% leak-down you may see the brown areas on the ring face where the chrome has been burned away or decreased end gap due to a collapsed ring.


Aluminum rods are the choice of champions. You won’t need a longer rod unless you get them at bargain prices or intend to build an all-out class engine. As mentioned a billion times (per Carl Sagan), we’re not looking for a few hp and for what we’re doing we certainly don’t care about piston dwell time at TDC.

I recommend purchasing new rods – it’s not worth taking a chance. If you must run a used set have them Zyglo’d and replace the bolts with a minimum ARP2000 or equivalent. ARP L19 would be the best if running a heavy assembly (alcohol) or a lot of rpm. Remember to check and record the rod bolt lengths before installation.

If you are utilizing 331 or 354 aluminum rods, you will benefit from my Chamfer and Pin Drilling Jig. It has a diameter that can be chucked up in a lathe for adding the chamfer. Check out the “Products” section. While you are there, check out my Adjustable Connecting Rod.

Steel Rods – Steel “H” beam rods are becoming more popular and are available for under $700.  In December 2012, Hot Rod Magazine made a comparison of small block Chevy rods. Eagle Specialty Products listed three rods capable of 1200 – 1400 hp. They don’t have the rod bearing pin but may be worth a try. Eagle claims the pins aren’t necessary – I disagree! Would you rather have the bearing rotate in the rod or have bearing material on the crank? I had the nut that holds the pressure regulating spring in the oil pump come off half way through a run. The only thing left of the bearings was copper. The rods were fine – no discoloration or out of round and didn’t spin. I took 400 sandpaper to the nitrided crank and it was perfect. Kiss a non-nitrided or chrome crank goodbye! Eagle’s big block rods are about 800 grams which is comparable to an aluminum rod but you’ll need to hone your pistons for a .990 pin. A friend in our association (WFA) has been using steel rods in his supercharged alcohol Chevrolet for years. He does change the rod bolts every couple seasons.

Rod BoltsUnder normal race conditions aluminum rods rarely break. It’s usually a rod bolt that fails due to excessive stretch. Check the free lengths when new and record. Electrically etch the length on the head of the bolts. Good Vibrations sells the dial indicator setup shown to check rod bolt stretch (T-1158). Their number is: 800-576-7661. You’ll need a “standard” (something of a known length) to set the dial. I use a discarded 2″ rod bolt. Make sure the end of the bolt is perfectly flat. Use a depth micrometer to check the distance from the end of the bolt to under the head. Say it is 2.005. Insert the bolt in the checker and then set the dial to read .005. Save this bolt for checking each time you use the gauge. Note: Some bolts have a hole in the end so use the indicator end that is gradually rounded (almost flat). The reading in the picture would indicate a bolt of about 1.971 in length.

There are many conditions that lead to rod bolt stretch. When I was running supercharged gas, the pistons were practically flat tops to provide 8 ½:1 compression with M/T rods. This combination was fairly light allowing 9000+ rpm without bolt failure (100+ runs). If running alcohol with a smaller displacement engine, the dome of the piston is much heavier due to requirement for 10:1+ compression. In addition, rods purchased today are generally much beefier (heavier) than my old M/T rods. This combination adds up to a much heavier assembly – one more likely to stretch the bolts. Larger displacement engines may be less prone to rod bolt stretch due to a smaller dome and a lower operating rpm. I say “may” because additional stroke also adds to piston speed and therefore stress on the bolts. The formula for piston speed is stroke x rpm divided by 6 = feet per minute. A safe number is usually 4500-5000. My gas combo is 3.625 x 9000 divided by 6 = 5438 – slightly over the safe limit. Lets look at a 392 with a ½” stroker at only 7800 rpm. 4.406 x 7800 divided by 6 = 5728 – considerably over the safe limit. As you can see the 392 would have to be run about 7400 rpm (5434 fpm) to compare with my 354 – even less to be in the safe zone. These calculations don’t consider the weight of the assembly – a lot to think about. Note: Keep in mind we’re not talking class racing where we may want to buzz this thing 10,000 rpm like a NHRA Pro Stocker. Our limiting factor is the bore in trying to squeeze out more cubic inches. For illustration purposes let’s take the 392 above (4.060 bore x 4.406 stroke = 456 ci) and twist it 10,000 rpm. 4.406 x 10,000 divided by 6 = 7343 fpm. Wouldn’t last long! Compare that to a 500 ci Pro Stock engine with wide bore spacings where the bore is 4.700 and the stroke is 3.600. So, 3.600 x 10,000 divided by 6 = 6000 fpm. A pretty safe combo given the availability of quality components.

Check your rod bolt lengths in a free state – then after 6-8 runs. More often if you run a lot of rpm or accidentally over-rev the engine. If you note any stretch of .002, record and reinstall. This is my recommendation since I have seen bolts stretch .001-.002 and then take a “set”. Every bolt manufacturer will give a different answer as to when replacement is required. I replace a bolt when I see the length exceed .002. If you’re one to go all season without pulling the pan, you’re looking for trouble. Better to catch a stretched bolt early.

Most rods come with at least a ARP2000 bolt. If you’re going to be running a lot of rpm and/or a heavy rotating assembly I would opt for the ARP L19 bolts at the first sign of stretching. They are about 50% more expensive but will last longer. I keep an extra set around and replace one at a time as needed. Manufacturers will tell you not to keep removing and re-installing the same bolts. I haven’t found this to be a problem but after the first removal where you check all (8) rods, you can go to removing two pair of rods at a time. So cylinders 1-4 this time, and 5-8 next time.

 Rod bearings – If you’re running a standard 331-354 size journal you will likely need to drill the bearings for the rod pins. If the rod journal fillet radius has been increased, chamfering the bearings to permit sufficient oil flow is mandatory. As mentioned above, check out my chamfer/drill jig in the Products section. This tool makes drilling and chamfering easy. Bearing selection:    Stock size journals = Clevite 77 CB378P (P=pin for aluminum rods) or King bearings.  Big Block Chevy = Clevite 77 CB743HND or if you can find them CB956P.  Small Block Chevy (2.100) = Mahle CB663HND (N=narrow, D=dowel pin).


Yes the ‘55’s are the best (see the Gene Adams write-up online). My first set were ’56 Mondello heads and I burned up a lot of parts. In the mid-‘70’s Steve Woods sold me the record holding heads off his BB/A. These were ’55 heads. I saw an immediate improvement in power as well as fewer burned pistons. These heads were done by Gromm in the bay area. Out of curiosity, I recently had the heads flowed and found the intakes were 313 cfm @ .600 lift and the exhaust at 235. Not bad for the ‘70’s.  The valve sizes are 2.200 x 1.920. Valve length is 5.150. I still run them*. Springs for my .600 lift Engle flat tappet are Comp Cams #917 and set to 210 lbs on the seat and about 550 – 600 lbs open. For my .647 lift roller they are set to 280 lbs / 650 lbs.  Most of the junior fuel guys use Bob McKray. He’s in Mission Viejo, CA. Plan on spending about $3K for some good flowing iron heads. Nick Smithberg (Smithberg Racing) has a CNC program for the ’55 iron heads and claims 400 cfm. He gets about $3K for the porting. Nick also has a CNC program for the aluminum Hot Heads. Nick did the porting for the early hemi in the Engine Masters Challenge. An impressive second place finish. Note: The spring pressures noted are for my assembly which utilizes .046 wall pushrods. Most assemblies will utilize .060+ wall pushrods necessitating an additional 20 – 30 lbs on the seat. Flow numbers – I’ve listed some pretty impressive flow numbers. If utilizing a .600 lift cam, one would have to question if a higher flowing head would be cost effective in respect to power gained. Only a dyno would tell whether there’s too much head for the cam.

*2012 – After running the cast iron heads for 40-years I finally managed to destroy one with a broken valve. I now run some old Webster aluminum heads with a high rise manifold. These are run dry (too many water leaks). They flow 365 cfm @ .700 lift on the intake and 290 cfm on the exhaust.

If you want aluminum heads, Hot Heads makes an affordable set in either solid or water jacketed but you will still need someone like McKray or Smithberg to work them over if you want an increase in flow. I see Webster is making heads again. See

Plugging water holes in the combustion chamber side of the heads – I have chased water leakage problems around for years. Although mainly around the 3/8” splayed main cap holes in the block, problems can also occur with the head gaskets as noted below. If running a race engine, the best way to eliminate this problem is to plug the holes in the combustion chamber side of the head with stainless socket head pipe plugs. If at some time you want to run water in the block, the stainless plugs can be removed. The smaller holes can be tapped (1/8-27) without drilling. The larger holes must be drilled out to 37/64 (.578) for a 3/8-18 pipe tap. You’ll also need a bottom tap for some holes. There are also small holes at the top and at the centerline of each chamber. They’re about .200+ in diameter and usually rusty. I cleaned each of these holes with a small round wire brush until all deposits were gone. I then turned aluminum plugs on the lathe about 1/2” long with .002 taper and drove them in. Unfortunately each plug must be custom made due to differences in the diameters. Use sealer on all plugs. An alternative might be to ream all holes to the same size. This would eliminate the necessity to make different size aluminum plugs.

Note: Some of the 1/8-27 holes are located close to the external step in the casting. Likewise, internally the casting steps in. When tapping these holes, the tap will start to angle when it hits this step. Proceed with caution so as not to break the tap. With sealer on the threads the plugs will still seal fine.

Here’s some general comments on assembly:

  1. Retainers can be a little smaller in diameter than the spring without affecting function – say 1/8″.
  2. Keepers – I have received some bad keepers recently so look them over closely. Buy (2) sets at a time to pick the best. About half of the keepers on two sets from Comp Cams were too small in diameter to fit around the valve stem. On another set from Manley I found the protrusion that fits into the groove on the valve stem was only .003 whereas others in my “collection” protruded about .010. I had Manley check their design and they found the protrusion was designed at .010. I received a letter indicating .003 was OK to use as the protrusion was only used for locating in the groove and the taper kept everything in place. This was not news to me but in case of valve float wouldn’t you rather have a little more tang in the groove? I threw them in the trash. When assembled, there should be a gap of say .020 between the two keepers. If the gap is close to zero, grab another keeper (or two) until you find a combination that provides a gap.
  3. The bevel on the outside edge of the spring goes up.
  4. Lube all parts including springs and shims prior to assembly. I use Comp Cams valve train assembly spray.
  5. I use a large heavy duty “C” clamp with a spring cup brazed on the spring end. When you tighten the clamp the valve stem will usually be slightly off center in respect to the retainer – this is good. Tighten just enough to get one keeper in the tight side. Push a little on the spring if needed. Add the second keeper and hold in place with a small screw driver. While pushing on the keeper, tighten the “C” clamp just enough to get the keeper to snap into the groove. Slowly back off “C” clamp while watching keepers. This process minimizes the frustration of having keepers falling out on the floor. Whack the tip of the valve two or three times with a plastic dead-blow hammer to seat the keepers.
  6. Here’s something that may be of interest. Lash caps are never a perfect fit for the valve. As such, they rock a little as the rocker arm moves across the cap. This rocking will eventually eat into the valve stem necessitating new valves even when the head of the valve is good. I recently purchased some Manley intake valves with an extra .100 above the groove (.300 total) and hardened tips. The additional height eliminated the need for lash caps. I’ve got about 40 runs on these with no problems so far.

Restricting oil flow to rockers – For a race application it is a good idea to restrict oil flow to the rockers thereby reducing oil to the top end and maximizing oil to the bearings. Drill and tap the oil hole in the head under the rocker stand area or combustion chamber side (both heads) with a 1/8-27 pipe tap. Use a socket head pipe plug. Drill a 1/16” hole in each plug and insert in head. If using needle bearing rockers, slide the rockers to the side and apply assembly lube before installing. Repeat at each engine disassembly – just an added precaution. Racing only – I have a second set of needle bearing rockers with no oil hole in the stands. These have been run on and off for 20 years and are fine. I put assembly lube on the shafts a couple times per season.

Head Gaskets

For anything under 750 hp (street or strip) you can run o-rings with  copper/composition gaskets (they seal water better). If you can find them, you can also run the steel/composition gaskets. I never blew one of these gaskets when running supercharged gas. I still have a few sets of the original Fitzgerald steel/asbestos gaskets for the 331 (3.875) and 354 (4.000) – check out the “Parts for Sale” section. When utilizing the copper or steel composition gaskets make sure the o-ring is inside the lip where the copper/steel is folded over.

If you run alcohol or nitro you’ll need the solid copper gaskets. I run .043 SCE gaskets. It doesn’t make any difference how “dead soft” the gaskets are they will not seal the oil and water effectively. The use of massive amounts of sealer is not a good idea since you will want to re-use the gaskets and you don’t want to tweak them out of shape getting them off. SCE makes a gasket with a bead of rubberized sealer around the water holes, but once used, the bead is gone. You’re kinda stuck. In my case I have the water holes on the combustion chamber side of my heads plugged so my main concern is oil. These areas are: 1) Oil hole to the rocker arms at 80 psi. 2) Drain-back holes 3) Crankcase pressure causing seepage around the pushrod holes. For items 1) and 2) I use a 5/8” diameter hole saw to cut around the existing holes in the gasket – three places. Then it’s down to the hardware store for some 5/8” o.d. x .06 thick o-rings. For item 3) I use K&W Copper Coat (dauber) around the pushrod holes in the block, head and both sides of the gasket. Note: Copper Coat goes bad after a long shelf life. Shake well and open can at auto parts store. If green don’t buy it. Have them order a fresh can.

Rocker Assembly

Nothing fancy here. I’m still using the same setup I got with my first engine. Stock intake rockers and Donovan exhausts on stock height stands. This setup twisted over 9000 rpm with the gas engine. I have a second needle bearing set I use with the roller cam. This also has the stock intake rockers with Gotha aluminum exhaust rockers. I just can’t bring myself to spend $3000 when I have something that’s lighter and works great. If you are not running a lot of spring pressure, Hot Heads or Rocker Arm Specialist (530-378-1075) can rebuild your stock assembly and install adjusting screws in the rocker arms. You could call them to see if they can add reinforcing straps along the top edge of the stock exhaust rockers. If they can, you have an assembly that will work well with spring pressures up to about 500 – 600 lbs. (open) AND are adjustable – I can’t do that with mine! For those that want the best, or are going to a cam over .650 lift, manufacturers like Rocker Arm Specialist and T&D also do the aluminum roller tip assemblies. You’ll have to jack the spring pressure for these heavyweights.

For reference, the stock stands measure: Intake – 1.483 to centerline of rocker shaft, Exhaust – 1.943.

Note about stock intake rockers: I noted mine are stock – completely stock. I have some of the fancy intakes that are lightened, polished and treated (redish/brown in color). If you want to polish them to reduce the possibility of a stress crack – fine, but lightening is definitely worthless and only weakens the rocker. Even with my 2.200 intake valves, the exhaust will always float first. It’s just wasted effort.


I use 3/8″ Smith Brothers adjustable pushrods. With a stock rocker setup and solid lifters which are 1 1/8″ from pushrod cup to the base of the lifter, the pushrod lengths are 9 3/4″ for the intakes and 11 3/8″ for the exhaust. As mentioned above, the tubing wall thickness is .046. I recently talked to the rep at Smith Brothers about getting a couple spares made and they refused to make them with such a thin wall. Said they wouldn’t work. I was wondering how I could run something for so many years that didn’t work! Anyway, for lift numbers in the .600 range purchase .060 wall pushrods. With higher lifts and aftermarket roller rockers go with something in the .070-.080 range. Pushrods are expensive so make sure you mock-up your assembly with a pushrod specially made for checking. If you need one I can make one.


I still run my original hardface flat tappet cam. It’s an Engle F31 with .600 lift and 322 degrees duration (.020 checking height) and 108 lobe centers. For what we’re doing, anything in the 108-112 lobe center range will suffice. The comparable Engle grind in a roller was the L131 – a great supercharged gas or alcohol cam. I normally run the hard face to avoid the possibility of a roller failure as well as less weight. I also have a “modern” roller with the same duration, an aggressive ramp and .047 more lift on 114 centers. I didn’t see any improvement in performance. I’m back to running “old reliable”. Here’s the valve timing for the F31 at .050 checking height: IO=36 deg BTDC, IC=66 deg ABDC, EO=72 deg BBDC, EC=30 deg ATDC (282 deg duration). Delta Camshaft in Tacoma, WA has the master for this grind. If you want a “copy” you will need to supply a cast “blank”. Remember, 331/354 and 392 take different blanks – try Isky. Since you can no longer get a hardface cam (cast cam with brazed-in hard steel inserts), ask Delta about nitriding the cast cam. An Isky 590 is a similar grind and they will still grind them as of 2015. Note: If you decide to run a cam with lift above .650 you will need special stands with the rocker shafts moved higher and outboard to retain the proper geometry. Custom aluminum rockers will also be required to handle the additional spring pressure. If this is your plan, cam selection is endless.

Gear Drive

Here’s one area where I would spend a little more money on insurance. Get a gear drive. It’s not worth taking a chance on a timing chain in comparison to the damage that can occur if it breaks. I have a Donovan on mine but RCD also makes a nice one. Buy an extra lower gear so you’re not pulling it on and off if you swap rotating assemblies.  Note: Donovan no longer makes the fuel pump extension for their drive. If you find a used Donovan drive without the extension, Enderle makes extensions that register where the fuel pump mounts on the flat Donovan cover for stack injectors. I just noticed Good Vibrations now has a 5″ (B-2126) or 6″ (B-2128) extension that fits most Donovan gear drives. It looks very similar to the old Donovan extension.

Oil Pump

I use a stock oil pump with a square Milodon pickup. The spring has been shimmed to provide 80 psi. This has worked effectively for 9000+ rpm – meaning no spun bearings. You can also use a Milodon setup that utilizes a spacer and 340 pump. These are a necessity on stroker motors. For a stock stroke I prefer the stock pump as the pump registers in the rear main cap for a near perfect alignment.

I fabricate an oil pump pressure checker to make setting the pressure easy – Get it correct before you complete the engine assembly. Check out the Products section where there’s more info on the subject.

Note: There are two different oil pump mounting spacings on the rear main cap. If your pump does not match you can still use it by elongating the hole in the pump base flange closest to the pump drive shaft (white arrow) by .100. Elongate it toward the oil hole in the cap and parallel to the back of the engine. Some caps must also be milled to clear a hemi oil pump shaft housing so it can locate in the cap – black arrow.



Oil Pump Drive Gear / Intermediate Shaft 

Make sure you check for engagement of the driver and pump shaft. This is easier to do with the cam out. The drive gear wants to be seated when engaged in the pump tang. With the pump out, use calipers to check the depth from the top of the block down to the top of the drive gear – record for future use (around 3.770 on a 331-354). Then check after the pump is installed. If the pump is pushing the driver up, add a ground shim between the pump and rear main cap. If the drive gear shaft is only engaging by say 1/8”, compare the shaft length and pump shaft length to other stock parts to find the problem. The recorded depth is also helpful when installing drive gear/shaft with the cam and pump in place to ensure the drive gear is seated. Tap a 10-24 or 10-32 thread in the top of the drive gear so you can get it out if it doesn’t drop into the oil pump tang. Use threaded stock or long screw as a removal tool.

Oil filter

I use a System1 filter with AN fittings on each end. This does a good job without any drop in oil pressure. It has a screen inside that can be easily cleaned. Assuming no nasty bearing failures, what kind of debris are you most likely to find inside the filter? How about lint from the rags used to clean and assemble the engine. To minimize the lint, use closed loop towels or the common blue paper shop towels. I’ve included a picture so you can check out the trick brackets that holds the filter. If you need custom brackets made, let me know.


Lucas High Performance 20-50 Synthetic works best with my clearances (.004). In the 70’s Pennzoil was my sponsor. The bearings always showed some wear and tear. With the Lucas they look new! Lucas also makes a high zinc Racing Only oil but I don’t find it a necessity. Maybe a consideration if running a lot of rpm.

Note: Oil pressure as indicated above (80 psi) is the recommendation with the clearances noted. If you prefer an increase in bearing clearance then reconsider the oil selection – possibly straight 50W.


What it is? An accumulator is basically a cylinder with a floating divider inside. On one side you put say 10-20 lbs. of air. When you prime the oil pump, pressure builds to 80 psi. and the divider moves to fill the accumulator with oil. At 80 psi manually close the valve. Before you start the engine at the races, open the valve to prime the engine. Starting the engine refills the accumulator. Leave it open. When you reach the quarter mile mark, pop the chute and hit the brakes, oil pressure can drop to zero. As pressure drops, the accumulator dumps oil into the system until the pressure in the accumulator is depleted. By that time you have shut off the engine without damage. Try to plumb a 2 or 3-quart accumulator into the system. Most are made by Canton or Moroso. Remember to overfill the pan with the additional 2 or 3-quarts of oil. If you don’t have room for a 2 or 3-quart accumulator, use a 1-quart. Note: If possible, a remote cable shut-off is recommended for the accumulator. Before shutting off the ignition, close the accumulator to retain oil pressure for next time out to the track. If you change oil before each visit to the track and intend to prime the pump, the cable shut-off is unnecessary.


Mag or MSD?  Take your choice! I’ve run both and performance is the same. I ran the Vertex until I got the tip of the fuel squirt bottle caught under the injector butterfly – 10,200 rpm per the computer! It got me thinking about a MSD.

A Vertex magneto carries the nostalgic “look” and I wish I was still running mine as this is the only item on the engine that doesn’t look ‘60’s. Tom Cirello (541-948-0547) is the best at setting these up. Many of the used units floating around have weak coils. Never run a used magneto (or a once good one that has been sitting for years) unless it has been tested. There are a couple of negatives with the magneto: 1) no “soft” rev limiter like a MSD 2) electrical interference with on-board computers.

If going with the MSD, they make a distributor for the early hemi. I would buy the Cap-Adapt large cap for this distributor. Unless the blower (6.71) is set back on your manifold the large cap should fit. You will also need to remove the guts for use with a trigger setup – instructions included. I used the Digital 7 box, HVC-2 coil and Taylor ThunderVolt spark plug wires with the hemi ends.

For the trigger setup I used the following RCD products: long crank hub and bolt, 7” flat alcohol degree wheel with magnets, and left side crank trigger bracket with TDC pointer . You will need to make custom spacers for the trigger bracket – see picture.

To ensure an adequate electrical supply you can run a small ultra mini 50A alternator. The alternator crank pulley is mounted on the back side of the degree wheel (just behind the red pointer in the picture). The trigger pickup is an Electromotion (Dave Leahy) unit. If you’re turning the engine over with a conventional type starter, gap the trigger pickup at .035. The faster the starter turns over, the wider the gap can be.

MSD ProMag – For some reason I decided the Digital 7 wasn’t burning the fuel so I decided to invest $3500 in a 20 amp MSD ProMag setup (you don’t need a 44 amp). I bought mine from BR Motorsports (559-739-1515) because they have them in “Black” (I hate those red caps on a nostalgia engine). Mike Dunn Services (417-967-0528) makes the black anodized cross drive adapter for about $400. With the adapter, the setup is pretty tall. I fabbed the aluminum clamp shown in the picture and attached it to the top of my intake manifold for added support. For my low Cragar manifold I attached the clamp to the supercharger rear bearing cover bolt holes via an “L” shaped bracket. To date the ProMag hasn’t improved performance over the Digital 7 – save your money. As a side note, one of the guys in our group utilizes a standard MSD distributor with a HVC coil and runs well over 200 and in the 6’s so maybe all the concern for a trick ignition is wasted time.

Spark Plugs

Champion N57DR    Gap at .018 – .020 for a Vertex or MSD ProMag and .035 for other MSD boxes.

Spark Plug Wires

Taylor makes a nice pre-assembled set with black insulator tubes. They’re under “ThunderVolt 8.2mm Universal. The part number is 85089 (black).

Blower Manifold

I use the low-rise ‘60’s Cragar manifold. Other than port matching it’s original. If you buy an old style manifold you will need to add a burst panel kit to be legal. Good Vibrations sells them. You can eliminate the gasket between the manifold and blower by having the manifold machined for an o-ring. A blower shop or Good Vibrations can supply the correct o-ring material. If you decide to go this route, assemble the engine with manifold torqued. Use a real machinist’s straight edge to check for flatness. If it appears to have high spots, lap the surface with an old cylinder head or other flat object. Coarse valve lapping compound works well. In cases of extreme warpage, assemble engine without crankshaft and place on mill or grinder. Kiss off manifold face. To test, mount blower without gasket and torque bolts. It should rotate freely. If you hear any binding of the rotors do not  run. It could also be due to warpage of the blower face. Machine mounting face and try again.

As noted in the “Head” section, I am now running a fabbed high rise manifold (2012) as shown in the picture above. See Ignition.

Tap 1/8-27 in rear of manifold for a boost gauge. Plumb in a pressure relief button like you see on superchargers. If you prefer you can run an electronic Autometer gauge or an inexpensive Auber digital gauge (ebay). They are less susceptible to pressure variances or breakage from vibration. Neither my data recorder or gauge agree on boost. I usually take an average.


Again, nothing trick here. It’s a stock 6.71 with hard anodized case and rotors – no Teflon strips. The bottom clearance is .003-.004. Don Hampton did the work in the ‘70’s. I also have a Dyer 8.71 stripped blower but haven’t seen any improvement. There’s a trade-off when going to a larger blower and using alcohol. On a small engine they take more horsepower to drive which may negate any horsepower gained by improved efficiency and the small amount of heat eliminated.  Another consideration is engine size.  You wouldn’t want to run a standard 6.71 on a 500″ engine.  If you’re running gas in NHRA competition a 10.71 on my 365″ engine would definitely be better to reduce intake charge heat and improve efficiency.

Fuel System

I use my Hilborn horizontal 4-hole from the ‘60’s with a 150-1 pump.  The pump puts out 100 lbs. @ 4000 rpm. For best atomization of fuel shoot for 100-120 psi max pressure – yes you’ll need a gauge or another sensor on your data recorder. Pressure is adjusted by nozzle size. If pressure is below 100 psi you can decrease the nozzle size one size on one or more nozzles. If over 120 psi increase nozzle size or maybe add an extra nozzle at the rear of the hat. Warning: For Hilborn or Enderle pumps, excessive fuel pressure is hard on the pump (no front rotor support).

Nozzles: (4) – 27A nozzles for gas engines under 400”

(8) – 40A nozzles for alcohol. No port nozzles or high speed bypass – just something else to fiddle with. Wait until you’re comfortable with alcohol then give it a try.

(8) – 47A nozzles for low percentages of nitro.

Don Enriquez at Hilborn can give you the correct setup for your application. Note: If you purchased used parts, DON’T RUN THEM until you send the injector and pump in for a checkup and calibration. Here are some of the things you can encounter with used parts: 1) Barrel installed backwards. 2) Cover on pump installed incorrectly – the cover position is set depending upon rotation – front cover or belt drive. 3) Pump no good or low pressure. 4) Linkage not set correctly. 5) Butterflies not closing all the way.

Eliminate as many variables as you can before you try to fire-up for the first time. If purchasing a used pump, negotiate paying the shipping to and from the manufacturer for a checkup prior to final payment. Hilborn can not rebuild a bad pump – you’ll need a new one. The best price on a new pump is from Their number is: 615-457-3192.

If you want to run my setup but prefer Enderle hardware, they can easily cross-reference. Just make sure you ask for a “rich” setup as a starting point. If running gas you won’t need port nozzles as you want the gas to provide a cooling effect as it passed the blower rotors. If running alcohol, port nozzles are OK as the nozzle size is large enough to pass small particles of dirt. Port nozzles are a good way to individually tune each cylinder via the EGT readings. A high-speed lean-out is a fine tuning device designed to bypass fuel (like the main jet) as the fuel pump supplies too much fuel to the engine at high rpm. See the Tune-up section for recommendations on jetting changes. On alcohol engines, a secondary bypass (comes off barrel) may be necessary to avoid going past center with the barrel adjustment and relieving pressure with the butterflies closed (See Tune Up section).

Nozzle orifice size on Hilborn 27A is .040

40A is .052

47A is .055

Engine Assembly Tips 

Assuming you have prepped your engine components as noted above there shouldn’t be any major surprises. I am NOT going to go over every detail.

Once you have cleaned the block thoroughly (brushes in all the holes, etc.), dry it off and wipe down the cylinders with a light colored rag or “t” shirt soaked in ATF. Continue to clean each cylinder until there is no black residue on the rag. Some say grit from honing gets stuck in the honing marks and must be thoroughly cleaned. If the rag looks good you’re OK – it doesn’t have to be perfect.

Install the oil galley plugs.

Install the upper bearing halves, rear main seal and oil bypass assembly.

Oil the bearing halves with assembly lube. I use PJ1 which is the old VHT formula. It can be purchased at Jegs. Note: Anytime I mention “lube” I mean assembly lube unless otherwise noted.

Oil all crankshaft journals and install in block. Place a piece of Plastigage on all main journals.

Install bearing halves in main caps – do not lube.

Install main caps and torque down being careful not to rotate crank.

Remove caps and check clearance. Anything between .003 and .005 is fine. Pick off Plastigage.

Install rear main seal and small rubber pan gasket seals in rear main cap. Add a tiny dot of silicone to the two rear main seal ends. Note: The installation of the rear main seal and pan are the only places in the assembly where I use silicone sealer. Where noted, “sealer” means Gaskacinch, Copper Coat, or your favorite.

Place (2) equal feeler gauges between the back side of the thrust bearing and the thrust surface on the crank. The feelers should point up and be snug but not tight.

If running water in the block along with 4-bolt mains, add some sealer to the (6) splayed 3/8-16 holes in the block.

Lube all bearings and install caps. Slide #3 down along the feelers.

When 4-bolt mains are used, tighten the ½” bolts (or nuts) just snug, add sealer to the 3/8-16 splayed bolts and install. Finish tightening all bolts. If you can’t remove the feelers, remove #3 cap and drop the feeler thickness .002. Reinstall cap.

Torque all bolts to manufacturers specifications.

Spin the crankshaft. If there are any tight spots, remove and locate problem.

Assemble pistons and rods. Assuming the valve pockets in pistons are the same it shouldn’t make a difference how you assemble them. Hold each assembly up to the engine, determine which side of the rod faces the cheek of the throw and place a mark at the top with a black marker.

Place rod in vise (protect with wood or ? – no shop rags) – black mark on piston away from you. Everyone has their favorite ring positions. The following works for me:

Starting with the oil ring assembly, place the expander gap at 6: o-clock. Place rail ends at 10: and 2:

Spiral the second ring onto the piston (start with the end of the ring perpendicular to the piston). Make sure the manufacturer’s identification mark is pointing up (or per their recommendations). Place the end gap at 6:

Note: You shouldn’t need a ring expander. There are some that say to only use a ring expander but I’ve found it very easy to over expand. The problem with the spiral method is carelessness – take your time. If the two ends of the ring line up after installation, you’ve done it correctly. If not, you may have to tweak the ring slightly.

Spiral the top ring onto the piston. Place the end gap at “high noon”.

Repeat for remainder of piston/rod assemblies.

Add some assembly lube to a rag soaked with ATF and apply a light coat to the cylinder walls. Now you know where all the lint in the filter came from.

Select the piston/rod assembly for #1 cylinder. Lube rings with ATF and rotate in  grooves. Wipe away excess ATF.  Reposition rings as noted above. Add assembly lube to the piston skirt, aluminum pin button ends and rod cheeks.

Add the rod bearing and lubricate. Lubricate threads in rod. Note: If threads are in a blind hole lubricate lightly to avoid a hydraulic crack. A good safeguard is to drill a small “through” hole in the bottom of the thread to avoid a problem.

Lubricate the inside of the ring compressor with assembly lube. Note: Don’t buy a cheap aluminum ring compressor unless it is hard anodized and smooth. The ARP compressors look pretty good. Most cheapies have a rough coating and the ring ends drag going in. My preference is to obtain a cylinder sleeve and cut it in half. Place in a lathe and turn a taper from about .150 larger than your bore down to about .005 larger than your bore. Use a fine stone cylinder hone or sandpaper hone to smooth the surface if rough.

Using “chop sticks” or other protective devices in the rod bolt holes, slide the piston/rod through the ring compressor.

Tap head of piston with a dead blow hammer while you keep quite a bit of tension on the “chop sticks”. Once below deck, twist rod to align with cheek on throw and pull into place. Make sure the rod end doesn’t hit the counterweight on the way in.

Add Plastigage to crank throw.

Add bearing to cap, lube bolt threads with ARP Ultra-Torque assembly lube, under head of bolt, seat in rod and both sides of washer (bevel toward bolt head). Install cap.

Torque to manufacturer’s specifications less about 7-10 lbs if using ARP Ultra-Torque. Most are between 70 and 95 ft. lbs. depending on the bolts used – or per stretch gauge if you want to be hi-tech. I don’t use one.

Remove cap and check clearance – .003-.004 preferred but not critical as it will measure different once engine is fired. If you see .001, PANIC!

Pick off Plastigage, lube bearing and re-install cap.

Tighten rod bolts but don’t do final torque.

Continue with remaining cylinders.

When all pistons and rods are installed, proceed to torque all bolts to manufacturer’s specifications. Less likely to forget one if all done together. Anytime you take a break, make a paper note as to where you are with the assembly (of particular importance if a member of the “senior” community).

Slide the four pair of rods side to side. If they move freely you’re “good”.

Rotate the assembly to check for any unforeseen clearance problems. If encountered, back to square one. If OK, rotate #1 around to approximately TDC.

Install oil pump.

Install baffle and pan.

Install a large degree wheel. I recommend one like a Comp Cams 16”. Locate TDC – refer to on-line instructions from Internet – there are hundreds. Use a 1” dial indicator on a magnetic base. A cheap dial indicator is available on e-bay, Harbor Freight or ??? You will also need it for degreeing the cam.

Install cam “straight up” or a couple of degrees advanced to start. To get the cam in roughly the correct timing, I install my F31 at 5 degrees before TDC on overlap where both lifters are level. Each cam is different so when you get it dialed-in, find where the lifters are level, make a note of the degree wheel setting for next time.

Install front cover if not already done.

Re-install degree wheel at TDC.

Remove tip on indicator and replace with welding rod long enough to reach pushrod cup in lifter. Position in center of intake or exhaust lifter. Zero indicator.

Check valve opening and closing events per the cam card supplied with the cam. These will normally occur at .050 rise on your indicator unless otherwise noted on the cam card. If within +/- 2 degrees you’re ready to go (best to be a little advanced – cam begins to open sooner than degree on cam  card). If not, adjust cam or crank gear as necessary. If you feel like fiddling with cam timing do it later. I think you’ll find it isn’t necessary at this time since there are too many other variables affecting performance.

When finished with the cam, move crank/degree wheel CLW to 27 degrees BTDC (#1 cylinder with both lifters down).

Add engine oil through valley and install valley cover.

If using head studs, lightly lubricate threads in block and run them in just a little tighter than snug. Do not over tighten or drench in oil as this could cause the block to crack.

Clean block, heads and head gaskets with lacquer thinner.

Copper Coat block, heads and both sides of head gasket around pushrod holes only. If running water in heads and block, goop all surfaces. Allow to dry at least 15-minutes before assembling.

Add head gasket to block. And, if going my route, three 5/8” o-rings.

Lower head into place. Stop just shy of seating and check the o-rings to make sure they haven’t come out of the gasket. If OK, continue down.

Repeat for opposite side.

Lube valve and rocker tips as well as pushrod sockets and install rocker assemblies.

Lubricate both sides of washers along with bolt or stud threads/nuts.

For ½” studs, torque the top row to 105 ft. lbs. and the bottom row to 90 ft. lbs. The bottom row is closer to the edge of the gasket and requires less pressure to ensure the block and head surfaces are parallel after torquing.

If using 9/16” studs, I would torque the top to 130 ft. lbs. and the bottom to 110 ft. lbs.

Install intake manifold and torque grade 8 bolts or cap screws to 37 ft. lbs.

If utilizing a MSD trigger setup on driver’s side, move trigger pickup until top of pickup diameter is just below magnet.

Pre-oil engine with driver and drill motor. Check for proper oil pressure and fill accumulator if not previously done. Remove driver. Check for leaks. Note: Driver should have a scribed line on top that is in line with slot in bottom. If there is no scribed line, add one so you can tell where to position the slot in the pump.

Turn oil pump with driver until scribe line is at about 2:30 (looking forward).

Position slot in drive gear/shaft at approximately 3:30 – 3:45 and drop into place. The slot should end up at about 2:50 when seated properly. These numbers may vary on your setup. This procedure is only to place the mag wires in approximately the correct position – facing forward. If not a concern, just drop it in anywhere. Check depth down to top of gear as recorded in Oil Pump Drive Gear/Shaft.

Install supercharger.

Install crank trigger distributor. With the centerline of #1 terminal in cap transferred to the distributor body, rotate body until the rotor is centered on the mark. Move rotor in both directions to center.

If using a magneto (not MSD) for racing it should be locked out (no centrifugal advance). Pre-set timing with a “buzz box” or you can make a cheapie utilizing two wires, flashlight bulb and batteries. Connect one wire to the case and one to the side “kill” terminal (kill wire removed). With the rotor between cylinders, the light will be illuminated (points closed). While applying a little pressure to the rotor against engine rotation, rotate mag body until the light goes out (points open) at #1 cylinder and 27 degrees on your degree wheel. Warning: Don’t get your hand close to the standing coil wire while adjusting or you’ll be picking yourself up off the floor. Tighten distributor clamp. Install cap. Make final check with self powered timing light (like a Flaming River FR1001 or MSD) and engine running.

Add remaining accessories, etc, etc, etc.

Place assembly in oven and bake for 45 minutes at 375 degrees – just checking to see if you’re still awake!

OK, I guess we’ve got it! Proceed to the “Tune up” section.


I’ll cover some general information first followed by some specifics for my gas and alcohol applications. If you have questions by all means ask especially if new to a supercharged setup. Best not to assume you can do some tweaking at the track and figure it out on your own. This is a formula for disaster – think I heard this phrase somewhere before. Most manufacturers like Hilborn or Enderle can get you pretty close on the setup for your specific engine as well as explain how the individual components function. A phone call could save your engine.

On-board computer – If you have the resources ($$$) I would invest in a computer from a reputable company. The more you spend the more features you get. On the high end units you get (8) exhaust gas temperature (EGT) sensors. The “ideal” temperature doesn’t always equate to the best performance. They are good for pinpointing your mistakes. For example, if you burn things up at a certain exhaust gas temperature at least you know enough to back things off to avoid doing it again. Make sure you get a pressure sensor for blower boost. I also “T” into the same line and use a gauge with a pressure relief button or electronic gauge. The computer and gauge never agree so I usually take an average. The gauge also gives you a quick visual.

EGT’s and alcohol – I use a max temperature for tuning. You may ask: “What is the preferred max temperature?” I don’t know! Having said that, I will explain. I have tried three (3) different EGT devices. My computer may say 1300 degrees (average) while my dual pickup FAST unit says 750 degrees. A dual pickup (unknown brand) I borrowed from my cousin says 1000 degrees. Many will say 900-1000 degrees is preferable (gas would be 300-400 degrees higher) but which one do I believe? It’s really not important. You need a performance baseline. Start on the low side (temperature) and gradually lean on it until you see a positive difference in performance. When you get to the point where a jet change makes little or no difference, you’re probably close to the “sweet spot”. Once you’ve achieved maximum performance your baseline is established. Note the max EGT reading and shoot to maintain this reading mainly through pulley and jet changes. If most of your racing is done at about the same altitude +/- 1000 ft. I would just use your weather station to make a jet change and leave the pulleys alone until you gain experience. Due to changes in atmospheric conditions don’t expect to run the same times as your baseline but this method should keep you from burning things up.  Summary – Any EGT system would be acceptable as long as you establish a baseline. If you can’t afford an on-board computer, go to ebay and purchase (2) digital EGT displays (one for each side) from Auber. They are a little over $100 each and will assist in the tune-up. These units have an output for a warning light. I set mine at 1300 degrees. If you see the light, shut her off.

Purchase a hand held weather station. I use a CompuTech. Once you enter your nozzle size and baseline main jet (pill) diameter, the unit will display all kinds of good data. You will mainly be dealing with the air density ratio (ADR). The ADR can change drastically throughout the year at the same track. Using your baseline data, the weather station will calculate changes in your main jet based upon current weather information. If you change tracks with a big difference in altitude you will need to change your drive pulleys accordingly to maintain a similar air/fuel ratio (AFR). This weather station is not sophisticated enough to make both calculations. When racing at a new track with differences in altitude and ADR, you may need to establish a new baseline for your weather station.

Tune-up program – As noted above, the weather station is not capable of accommodating changes in the weather AND a pulley change as would be required for altitude changes or to tune for an index class. For the last (3) years I have been using a tune-up program available from Jim Maroney at American Flowtech ( Once your baseline is established, you can enter the weather data and any pulley change to obtain the correct main jet. If you are going to be making pulley changes, this is a “must have” program.

Purchase a leak-down tester. In addition to leakage past the rings, the tester helps locate leakage at the valves. When comfortable with your AFR and performance, do a leak-down every couple runs (every run if making jetting changes without the use of a tune-up program). If running supercharged gas, do a leak-down after each run. If lean on the main jet, the additional heat can take a significant amount of tension out of the rings in addition to scuffing piston skirts, etc. You want to catch it early. A rich condition just slows things down. If running alcohol, a lean condition is definitely “not desirable”. A rich alcohol mixture is more forgiving – no big change in performance if jetting is in the ballpark and zero ring problems. Note: I recommend a leak-down tester that is capable of 100 lbs of air supply. Some of the cheap ones and even Snap-On are low pressure. You want higher pressure to “snap” the rings against the cylinder walls as this is what happens in a running engine. Mine is an old ’70’s Child & Albert with a single gauge. I set the regulator on the compressor to 100 lbs, adjust the needle to zero and have at it.

Important – NEVER run a supercharged gas engine with iron heads unless water is circulating in at least the heads. Without water, the intake charge will be super hot and you will sneeze the blower – guaranteed! Aluminum heads will dissipate enough heat to work OK but you have no control over the head temperature. I recently tried running my cast iron heads without water when utilizing alcohol – worked fine as the alcohol provided enough cooling to preclude a “sneeze”. They were cracked and leaking so gave it a shot without water. I was also able to remove about 60 lbs ( radiator, pump, etc ) from the car. The downside would be making the final rounds of eliminations. The heads are still pretty hot after a half hour or so. You could devise a remote setup to pump water through the heads between rounds – 10 minutes would do the trick.

Valve settings – With a new setup I would check the valves after each of the first three runs to see if there is any movement (like something wearing or a bent pushrod/valve). If OK, button it up and forget about it unless there is a noticeable change in performance. Some fiddle with valve settings after every run – not necessary with cast iron heads and block unless you over rev it. If running a roller cam and/or aluminum block or heads, more frequent valve adjustments will be necessary. Note: Don’t let this information discourage you from checking the valves after every run, time permitting! I’ve been running my combination with a flat tappet cam for over 40 years and have yet to have a change in valve lash adjustment with iron components. Having said that, I once had the push rod come off. Leak down was great but only running on (7) cylinders.

Hilborn barrel valve setting on gasoline and alcohol – The shaft of the barrel valve (or rotor) has a screw driver slot that is generally perpendicular to the direction of fuel flow at idle. When the throttle is wide open, this slot should be in-line with the fuel flow. If set at the factory, the barrel is usually set at a percentage of leak-down. Prior to your first “fire up”, note the position of the hex turnbuckle with left and right rod ends connecting the butterflies and barrel valve. Mark one of the flats for reference. Shortening (moving the barrel valve lever in the direction of full throttle) richens the mixture at idle. Lengthening the distance leans the mixture. After the engine is warmed up, quickly flick the throttle by hand at the injector (about ¼ open and immediately closed) . If the engine hesitates (lean mixture), shorten the distance between the two rod ends until the engine quits hesitating, then turn the hex two additional flats. If on first time startup the engine does not hesitate, lengthen the distance until it does and then richen two flats. If your car is equipped with an automatic transmission and you are having trouble setting the barrel, get it as close as you can and then put the transmission in gear and do a stall test (on jack stands). If the engine starves for fuel (too lean) when you open the butterflies momentarily, richen the barrel until it quits and then give it two more flats. Note: The barrel setting has no effect on full throttle fuel flow unless you adjust way past where the screwdriver slot is straight across. A note on supercharged gas engines: A rich gasoline mixture is indicated by black smoke. If on initial startup the engine is puffing black smoke, lean the barrel until the smoke almost diminishes then proceed as noted above to fine tune the idle mixture. After the final adjustment to the barrel, note the position of the screwdriver slot at full throttle. If it goes past straight across you may need a secondary bypass – this is not normally required when running gas. I’m now running alcohol so my secondary is set to 6 lbs from the factory. Add a couple of the thin shims (more fuel on idle) and re-adjust the barrel to lean the idle mixture. Readjust until slot position is straight across. If using alcohol, milky oil is due to a rich idle mixture. Lean the idle mixture and recheck the oil. Diluted oil reduces the lubricating quality and must be avoided if possible. If this condition exists, you can contact the injector manufacturer for the proper barrel leak-down for your size engine. With alcohol you will always experience some condensation under the valve covers and in the pan. This is why it’s a good idea to remove both valve covers and pan when you return from the races.

Jetting – general comment. When making jetting changes consider the “area” of the size pill you will be changing. Let’s say you make a run using a .125 main jet. You check your plugs and find you need to go a little leaner (larger) on the main. .002-.005 larger would be the recommendation rather than .010 because the increase in area is substantial when up at .125. In contrast, let’s say you’re going to try for a little more speed by incorporating the “high speed”. Unless already running lean, you can safely go from a “blank” pill to a .030 because there is very little change in area at these smaller diameters.

Spark plug reading – No science here. As mentioned above, I set my EGT warning light to come on at 1300 degrees. This is on my leanest cylinder. You’ll have to move the EGT probe(s) around to find the lean cylinder. Since I have a pretty accurate tune-up program, the temperatures are always between 1250-1275. At this temperature I burn about 3/4 of the cad plating off the face of the plug. This is my sweet spot. On the next run, as a safety precaution, I install a new plug in my lean cylinder so I have fresh cad to check. In the last 50 runs the plugs always looks the same. In essence, I can run all year long and never change a plug. The downside is that a little more cad gets burned off with each run so eventually you can’t “see” a lean condition should it surface. Here’s a shot of a NGK B9es from my hottest (leanest) cylinder after 1 run. The arrow is pointing at the remaining cad plating. Warning: Spark plugs of other brands or heat range may show a different pattern. The NGK is out of my late model hemi and not the 354.

Timing – A supercharged hemi on gas likes 25-29 degrees total. If we were running a Chevy, an equivalent would be about 33-37 degrees. You can safely reduce the timing but I haven’t found it necessary to go much higher than 29 degrees. Alcohol is somewhere between 28-32 degrees. Any of the mentioned numbers will work fine.

Blower boost – If a supercharger is new to you, I would recommend around 17 psi boost as a starting point for racing and 6 – 8 psi for the street. After you get a little experience, you can “jack it up”. If you arbitrarily run the blower faster (smaller top pulley or larger bottom pulley), remember to richen accordingly. Your tune-up program will get you close.

Blower drive ratio recommendations in the examples below are for 350 – 365 cubic inches with a good 6.71.  If running a 8.71, slow it down about 10% from examples below. Disclaimer – Each engine combination is different and could lead to substantially different results. Start rich! The numbers below represent actual (good) runs at various air density ratios – use them as a guideline. Something to keep in mind: If you are running a 392 you will have to spin your 6.71 about 10% faster than for my 354 to produce the same boost. For a 450 incher, tack on an additional 15% over the 392. The higher ratios are pushing the effectiveness of a standard 6.71. For example, the 450 inch engine would run better with an 8.71 at 10% less overdrive as this would bring the percentage of overdrive more in line with the effective range of the blower and produce less intake heat. Heat robs power – especially if running gasoline. Note: As a starting point, Weiand has a boost chart for various size engines. It can be found at – Support – Tech Services – Resource Services & Library – Superchargers – Supercharger Tech Information.

Tune-up Recommendations with Hilborn 150-1 pump (see below) – Refer to your weather station for jet changes at different Air Density Ratios (ADR). Note ADR’s in the ’80’s are higher altitude tracks.

Supercharged gas: ADR = 100, Blower = 15% overdrive (boost = 19 lbs), nozzles = (4) 27a, main jet = .120, magneto = 27 degrees, fuel pump = Hilborn 150-1.

ADR = 88, Blower = 20% over (boost = 17 lbs), main jet = .150

Note: A super rich mixture on gasoline may miss or pop. If this occurs, lean the mixture (larger diameter Hilborn main jet) in .010 increments until it stops. If this happens, check your burst panel for a bulging condition. A super lean mixture will not miss – just burns things up.

Supercharged alcohol: ADR = 97, Blower = 14% (boost = 17 lbs), Nozzles = (8) 40a, main jet = .060, MSD = 27 degrees, fuel pump = Hilborn 150-1.

ADR = 80, Blower = 20% (boost = 16 lbs), main jet = .050.

For 7.60 class like NE1 with 2000 lb car: ADR = 94, Blower = 8% underdriven (boost = 12 lbs), main jet = .070, MSD = 22 degrees. This is my low altitude (west coast) tune-up.

Supercharged 10% nitro:  10% Nitro: ADR = 91, Blower = 17% (Probably better at 14%), Main jet = .030, Nozzles = (8) 47a. MSD = 29 degrees. Ran 4.54 @ 150.1  1/8 mile.

20% Nitro: ADR = 85, Blower = 17%, Main jet = .030. MSD = 27 degrees. Ran 7.31 ¼ mile shutting off at 1000’ (nosed over) – Burned tip off of one plug (no piston or ring damage) – Hilborn 150-1 pump maxed out. The 150-1 would work OK on 10%. Need to upgrade to a Hilborn 175 for the higher percentages. If you go with a 175 pump start with a .120 main jet @ 20% nitro and and equivalent ADR. Nitro notes: Percentages up to 50% will work fine with 9:1 compression. However, these higher percentages will reduce the life of the engine block due to increased cylinder pressure in conjunction with the thin deck. If you decide to run a higher percentage you will need to increase the timing accordingly to compensate for the slower burn rate of nitro. As an example say 55 degrees advance for 50% nitro. You can prorate the timing starting at 30 degrees for 10% to get you in the ballpark. For safety reasons start at a conservative number.

Starting the engine – Place pan under pump. Remove line from pump to injector at the pump. Check for fuel. If dry, fill fitting with fuel and turn engine over by hand (ignition off) until fuel from tank spills over fitting. Reconnect line. Turn ignition “on”. Open butterflies. Using a pump type squirt can, squirt about 7-8 times into injector. Close butterflies completely. Hit starter. When engine starts to run, continue squirting fuel through the small crack where the partially open butterfly meets the injector casting until the engine is running smoothly. If engine dies, repeat process. If using an upright injector with scoop, just continue squirting into the scoop. I like the pump type squirt can because it is easier to control the amount of fuel. The “beauty shop” plastic bottles tend to dump too much fuel into the injectors. I use racing gas in the squirt can or a combination of gas and alcohol for the alcohol motor. Cold weather – use gasoline.

Alcohol – Add Klotz “Uplon Fuel Lube” to your alcohol. If used as directed there is no negative effect on performance. Klotz adds valuable lubrication to your pump, shutoff and barrel which alcohol lacks.

Engine won’t start – There are many reasons for an engine not to start – far too many for me to troubleshoot. BUT, If you are using a MSD unit with a standard starter, try moving the trigger pickup a little closer to the trigger wheel. I use the Chrysler gear reduction starter and run a .035 gap. The faster the starter turns over, the wider you can make the gap. A 16 volt battery is the way to go and you can use it safely with your 12 volt electronics.

Car runs way too fast and quick – A shit eating grin is a sure sign of a happy racer! Good luck.

After the race – If running alcohol you will need to flush the fuel system. If alcohol is allowed to dry it forms a residue that resembles soft wax. You don’t want this. I use a male AN fitting with air fitting. Blow air through all lines and injector barrel valve to purge all alcohol. Then squirt some Marvel Mystery Oil in all lines and injector barrel valve.  Again, blow air through the system to lubricate. After disconnecting the fuel source, squirt Marvel oil in the outlet from the fuel pump . Crank the engine backwards to lubricate pump. You should now be ready for the next time out. Note: If wax from dried alcohol is found, gasoline will dissolve it.

As mentioned previously, if you notice any errors, omissions, items out of sequence, etc. please let me know. Your comments are appreciated.

Check the “Revisions” section below occasionally as I am continually making updates, additions and/or corrections.

Thanks, Ed Middlebrook



 1) 1/25/11 – Original

2) 2/8/11 – Under “Installation of new and used 4-bolt main caps”, changed to: Mill #1 and 5 caps (if originally on block) down .010-.020.  See 14) below.

3) 2/8/11 – Under “Installation of used 4-bolt main caps”: added drilling and tapping instructions as in “new” installation – text missing.

4) 2/19/11 – Added warning under “Block cleaning” about possible interference between the large rear pipe plug and the distributor drive gear.

5) 2/19/11 – Under “Pistons” added a minimum piston to valve clearance note at item 2.

6) 2/20/11 – Block – Oil bypass assembly: Revised text for diameter of restriction (was .440) and removal of stock assemmbly.

7) 3/10/11 – Added “Spark Plug Wires” section and bottom clearance on blower.

8) 3/22/11 – Added text to “Blower Manifold” section for flatening mating surface.  In “Engine Assembly Tips” added ATF lubrication requirements to rings prior to installation.

9) 3/31/12 – Block / Block Filling – Modified block filling procedure.

10) 3/31/12 – Crank – added “Update” re: crank life.

11) 3/31/12 – Oil Pump – Added text re: poly block rear main cap modifications.

12) 3/31/12 – Tune-up / Hilborn barrel valve setting – Added text re: shimming the secondary if the barrel screwdriver slot goes past straight across.

13) 3/31/12 – Tune-up / Starting the Engine – Added note about priming injector pump.

14) 1/26/13 – Under “Installation of new and used 4-bolt main caps”, changed to: Mill #1 and 5 caps (if originally on block) down .005-.010. This came from my machinist as he would rather take more time dealing with the reduced tolerance thereby ensuring a better rear main crank and gasket seal.

15) 1/26/13 – Added section for “Rod Bolts”.

16) 1/26/13 – Added Nitro tuneup info.

17) 03/01/13 – Added EGT section under “Tune-up”.

18) 03/06/13 – Added MSD ProMag to “Ignition” section.

19) 03/12/13 – Added Intermediate Shaft Bushing under “Block”, Steel Rods under “Rods” and bearing selection under “Main bearings” and “Rod bearings”.

20) 04/09/13 – Added note on main bearing runout in the “Used cranks” section.

21) 11/24/13 – Corrected BBC rod bearing number under “Rod Bearings”.

22) 04/01/14 – Added F31 cam specs to “Cam” section.

23) 04/01/14 – Added “After the Race” in Tune-up section.

24) 04/01/14 – Changed ignition timing recommendations in Tune-up section.

25) 12/16/14 – O-ring / receiver grooves – added text for using (2) o-rings.

26) 12/18/14 – Added picture and text re: poly block under “Block”.

27) 12/18/14 – Added picture and text re: o-ring tool under “O-ring”.

28) 12/18/14 – Added picture and text re: rear mail poly cap mods for oil pump under “Oil Pump”.

29) 12/18/14 – Added additional text for modifications to used 4-bolt caps under “Block” and picture of 1/4″ endmill cut.

30) 12/18/14 – Added additional tune-up information under “Tune-up”.

31) 12/21/14 – Added picture of ProMag stabilizing clamp under “Ignition”.

32) 12/31/14 – Added additional information under Tune-up/Nitro notes.

33) 12/31/14 – Modified wording for checking stroker clearances under “Stroking”.

34) 07/13/15 – Corrected BBC rod bearing callout under “Rod Bearings”. S/B CB743HND or CB956P.

35) 08/01/15 – Added comment about a billet rear main cap under “Block”.

36) 09/21/15 – Added picture and text in “Rod Bolt” section.

37) 10/08/15 – Added “Note” about exotic prep of stock intake rockers.

38) 02/11/16 – Added recommendations for a leak-down tester under “Tune-up”.

39) 02/11/16 – Added comment about port nozzles and high speed lean-out to “Fuel System”.

40) 02/11/16 – Added comment about tip on indicator under “Rod Bolts”.

41) 07/27/16 – Added rod bolt recommendations under “Rod Bolts”.

42) 07/27/16 – Added “Assembly tips” under “Heads”.

43) 03/06/18 – Updated as much as possible to accommodate for lost data.

44) 03/13/18 – Updated numerous sections after data recovery. Should be close now.

45) 06/06/18 – Added note about using Klotz in your alcohol.

46) 12/13/18 – Added “Jetting” and “Spark plug reading” in the Tune-up section

37) 02/18/19 – Added stock rocker stand dimension to “Rocker Assembly”.

38) 02/18/19 – Added “Pushrod” section.