Inliners International Forums General Discussion Engines Need help with GMC 302 bellhousing-SM420

I got a good deal on a 1953 GMC 302 hoping to replace the stock 228 in my 51 GMC 1-ton. The 302 came with a bellhousing, 6 bolt flywheel, clutch, and pressure plate. The problem is that the bellhousing wont bolt up to the SM420. The top holes on the bellhousing are ~7.75" apart, bottom are ~ 7.25 apart. On the SM420 the top holes are 8.25 apart, bottom 9" apart. I cant use the 228 bellhousing because it isnt as deep as the bellhousing that came with the 302, so that there isnt room for the 302 pressure plate. I also cant just use the 228 flywheel and thinner pressure plate with the 228 BH (having the correct bolt pattern) because the 228 FW is 4 bolt and the 302 FW and crank are 6 bolt.

Any Suggestions

Izzenhood

Maybe have the GMC 302 flywheel drilled for the 228 clutch pack.I have a 270 GMC flywheel that came out of a cabover engine truck that has 9 bolts on the pressure plate with a Borg and Beck style clutch.Seems GMC used alot of different combinations for their drivetrains.
EvilDr235

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Two types of people drive old cars.Rich people because they want to and poor people because they have to.
Remember EvilDr235 has a cure for Your sixness.

You do have some options here, first being forget about whatever bellhousing and clutch came with the 302, it's way too heavy for use in a 1/2 ton pickup. Use the stock 228 1/2 ton bellhousing which **should** mate up OK with the 302 block but follow the shop manual procedure to dial indicate the bell housing to crank spec, adjust dowel pins if grossly out of alignment but chances are its OK. Your local clutch shop can reccommend a diaphragm clutch that will bolt up to your 302 flywheel (but a 270 wheel is lighter, same pattern). A B&B style (3 finger) clutch to match the GMC bolt pattern won't fit in that bellhousing, at least not that I could find.

Another option would be to obtain a SBC V8 nodular iron flywheel and have the flange and bolt pattern machined to fit the GMC crank. Then you have an unlimited variety of OEM and aftermarket clutches to choose from, cheap and plentiful. Ring gears are same as the GMC (12V) flywheel so starters should match. All of these clutches should fit the 1/2 ton bellhousing with no problems.

How about just drilling and tapping the 420 bolt pattern(stock Chevy, etc.) in the 302 bellhousing? Make sure the bellhousing has the correct retainer diameter.