I recently did some custom work for a Pete Robinson (PR) blower drive.
If you have one of these drives (or any other ‘60’s drives) and are missing parts, I may be able to help.
Pete Robinson cast adapter
Pete cast these thicker adapters because the Delta cast front cover with integral idler arm boss were thin and prone to breakage if the engine encountered a backfire. The adapter mounts to a stock supercharger front cover.
PR blower pulley mounted to a rear collar.
This later configuration shows the idler arm mounted to the blower snout.
Myth-Racing machined Rear Split Collar for supplied PR blower pulley
PR blower pulley mounted to the split collar and the one-off idler arm required to clear the pulley.
This is a 36-tooth pulley. The reason for the clearance problem and special idler arm is that PR cast his idler arm boss .550 closer to the center of the blower pulley than a Delta setup. In addition, the boss on his adapter is 2.500 in diameter compared to 2.750 for the Delta configuration.
Most of this work involves some research to find the correct parts. For example: The Pete Robinson adapter was bored for a 2.4375 O.D. deep groove ball bearing with a 1.375 I.D. This bearing is no longer available. After searching the internet and a couple of phone calls, a bearing was located with the same I.D. and a larger O.D.
Once the preliminary research is done, I draw up sketches of the work to be done to minimize mistakes. You’ll get a copy. Here’s a sketch pertaining to a PR 2” idler pulley. If you see an error or want something different, by all means let me know – this is a partnership.
The bearing I.D. was non-standard at .787. The fix was to turn a .787 O.D. x .625 I.D. insert for a 5/8 bolt as well as a rear standoff of the same diameters. This isn’t hi-tech stuff but takes time.
I will supply you with a detailed weekly status report including the cost of any supplies needed. I’ve included a few pages of an actual status report here:
Pete Robinson Project
1/30 – FedEx Shipment received.
Drive shaft, (2) idler pulleys, (2) blower pulleys, stock blower cover and Pete Robinson (PR) cover adapter received unharmed.
1/31- Time – 2 hr. Mock-up on my supercharger and determine to-do list. Supplied drive shaft running true within .001. PR 36-tooth pulley will rub big end of standard Delta idler arm. Reason – PR adapter – Center-line of pulley to centerline of 2.500 idler arm boss is .550 closer together than Delta setup. Will make special idler arm with smaller big end to clear – see sketch below. Ordered 1 3/8” aluminum stock for idler arm.
36 tooth PR pulley will need special split collar to mount behind pulley for attach from front as in picture of PR dragster. Layout shown in sketch below.
PR idler pulley (2”) will need existing shaft pressed out and .787 O.D. sleeve made for 5/8 bolt. Also needs a rear standoff
Idler pulley (3”) bearing has a .975 I.D. and will need a sleeve for a 5/8 bolt. Existing standoff will also need a sleeve to 5/8.
2/2 – Time – 1.8 hr. Researched and ordered National 7769 (or 6241S) seal for PR adapter on ebay. Called Timken.com for shaft bearing. No longer available in 2.4375 x 1.375. Will bore PR adapter to fit a Delta deep groove bearing.
2/3 – Time – 2.5 hr. Layout of rear split collar for 36 tooth PR pulley. Ordered 4” round x 1” aluminum stock.
Rear split collar sketch
Belt clearance with 36-tooth pulley and special idler arm
2/4 – Time – 2.5 hr. Completed turning and boring portion of rear split collar.
Week 2
2/5 – Time – 1.0 hr. Made fixture to press out 2” idler pulley shaft and removed shaft. Diameter through bearings is .787. Will make a 5/8” ID x .787 OD sleeve to use the same 5/8” bolt as the 3” setup. One snap ring to retain bearing is missing. Will order.
2/6 – Time – 4.0 hr. Completed (6) 5/16-18 holes, broached 5/16 key-way, added 3/8-16 for tightening split collar and completed slitting operation. Rear split collar/adapter complete. Allen bolts (6) 5/16 -18 x 1 1/2 to attach supplied PR blower pulley.
PR blower pulley adapter to split collar
As you can see by the above, there was an extensive amount of work. This just gives you an idea of the detail I will provide.
Can I give you an initial estimate? Likely not. I will need to see all pieces to determine work involved. For custom work, I get $50/hr whether it is finding parts on line, scratching my head, communicating with you, drawing sketches or machining. I don’t pad the hours – you’ll get the best deal possible. In the unlikely event of a break-in at my shop, I will not be responsible for any loss incurred. I do have insurance but the outcome is uncertain when dealing with these companies. To minimize the chances of loss, I do not leave these parts unattended in my shop. They go home with me.
Anything on my site such as a standard Delta split collar is a fixed price as shown.
If you have any questions by all means give me a call at 310-995-8224 or drop me an email at emiddlebrook@hotmail.com. I’ll be happy to help with your restoration.
Thanks, Ed Middlebrook