Drill/Tap Jig – 9/16 Studs

The addition of 9/16 studs provides an additional 30% increase in holding “pressure” on the head and therefore the head gasket. Higher compression ratios paired with an increased in blower boost can “squeeze” the gasket out between cylinders. Conversion to 9/16 studs acts as a safety measure to ensure you don’t miss a round of racing (well at least from a failed gasket).

This jig ensures each hole will be precisely located and perfectly perpendicular to the surface of the block.

In assembling items for this kit I have requested, and paid more for, “Made in USA” components. Help our economy by doing the same.

This kit includes a precision bored 3/4” thick aluminum jig, two button head locators, Slip Fixed (SF) drill and tap bushings, 31/64 drill, 9/16-12 3-piece tapping kit (taper, plug and bottom taps), (2) 1/2-13 hold-down bolts/washers, (2) 9/16-12 hold-down bolts/washers, anodized finish, storage case and complete instructions, including all the safety warnings you could care less about but should adhere to anyway.

Fits Chrysler

P/N   DT01   Drill/Tapping kit (standard):            $219 + shipping **

P/N   DT02   Drill/Tapping kit (o-rings in block):   $239 + shipping **

Reduced price – Drill & Tap jig for 9/16 head studs. Fits Chrysler, Dodge or DeSoto

This kit does essentially the same as the kits noted above at a reduced cost. Custom ground bushings are becoming very costly. As an example, the bushing for a 9/16 tap is about $60 (2018). I am making my own bushings from cold rolled steel. They won’t last for hundreds of engines but will suffice for what we’re doing. If you work on all three brands, this jig will accommodate your needs.

Kit comes with a 3/4″ or  1″ base plate, button locator, both drill and tap bushings, 31/64 drill, 9/16 tap, tapping fluid and storage container.

P/N   DT03   Drill/Tapping kit for Chrysler, Dodge or DeSoto:   $139 + shipping **

** Actual shipping charges only – no additional charge for packaging

Tip: If you look at the head bolt locations you will notice the bottom row is close to the edge of the head/block while the top (intake) side is set further in. The row closest to the edge will exert more pressure and therefore pinch the gasket more. To provide for a more parallel (equal) gap between the head and block I recommend torqueing the bottom row studs approximately 20 ft. lbs. LESS than the top row. After 2-3 engine teardowns check the gasket thickness top and bottom and adjust torque if necessary. If you are reading this and use 1/2″ studs, use 90 ft. lbs. on the bottom and 105 on the top.

Head Studs

I have discontinued selling the 9/16” studs. They are expensive to begin with and it would be in the best interest of the customer to buy direct.

Alan Johnson (AJPE) 805-922-1202 offers 8.650 oal studs. They are quality 190,000 psi pieces with rolled threads and a female hex on top for installation. There is about .200 on the bottom that is not threaded to ensure the stud “bottoms” in the hole and does not bind on the partial threads. I talked with Richard Wilkinson at AJPE about the cost to shorten (10) of these 1/2″ on the block end (they come with 2” of thread). Richard went to the shop and was quoted 1 ½ hours of labor for (10) studs.

If you contact AJPE you can refer to quote # 78991 so they can get a better idea of what you want. Here’s the breakdown from that quote:

(20) 9/16 studs p/n 11z-1058 @ $21.48 = $429.20

(10) 1 ½ hour shop labor to shorten 1/2″ @ $81/hr = $121.50

(20) 9/16-18 12pt nuts p/n 11z-2013-Al @ $4.24 ea = $84.80

(20) 9/16 HD washers w/ ID chamfer p/n 11z-2122 @ $1.00 ea = $20.00

Please note: Prices may have changed since quote.

These studs are a little longer than a “stock” length stud (8 ½”) but the top with the female hex is not threaded about .170 down so it comes out within .020.

NOTE: Standard height stands are: 2.060 on the intake side and 2.687 on the exhaust.

Keith Black also offers 8.750 & 9.260 oal stud that can be cut down to your specific length. They also have the .200 non-threaded protrusion on the bottom. The part number for these studs is 51287 and are $17.75. One of my customers indicated they fit his Titan setup.

For the unlimited budget, ARP has a 8.950 oal stud. This will accommodate any height stand as they have 2.400 of thread and can be cut off to fit. They are made of L19 material and can be yours for the paltry sum of $59.85 each.

Neither Titan or Donovan have 9/16″ studs for the early hemi.