I ended up buying a zoom clutch (kit 30043) for my 72 350. Was looking at some higher end clutch kits but motor rebuild ended up being $5,000 and running out money for this project .... https://www.summitracing.com/parts/zzz-30043 It came with a throw out bearing and pilot bearing. Summit says it works for a Buick 350. 1) I noticed the original throw out bearing has a triangle hump in it (see pic). What is the purpose of that and does it matter the new one doesn't have it? 2) I don't have the motor back yet but have see threads where people say the Buick 350 pilot bearing is an odd size. How do I know if I need to replace mine and any idea if the pilot bearing in the Zoom kit will fit? Thanks all!
The little hump in the groove is to prevent the release (throwout) bearing from spinning in the fork. Some bearings will have a pin instead for the same purpose . But they should all have something to prevent it from spinning As far as the pilot, you'll have to measure the hole in the back of the crank. A GM pilot bushing will measure around 1.097. If the engine wasn't intended to be a 4 speed, you'll find that the finish machining wasn't done at the factory and the hole will be smaller. On my 455, the hole was 1.085. More than likely you'll have to machine the pilot to the crank. Also make sure the hole doesn't have a "step" in the back of the hole. If so, you'll have to reduce the depth of the pilot bushing. Ask me how I know all this! Good pilot bushing will NOT be magnetic. If yours is chuck it and find a different one Is the block drilled for the z bar ball stud? Some automatic equipped blocks aren't drilled. Especially later 72 blocks
Ok thanks. I will measure it. The car was an original manual transmission car with a 3 on the tree so I assume the crank was factory drilled and have been running the 4 speed already for a few years no so yes the engine has a z bar stud already..... Thanks Jason!
The last Zoom brand clutch I used required too much pedal pressure. Something like a Dual Friction is a better choice.
Ah, I didn't realize it was a manual already. Definitely change out the pilot since you have everything apart. As far as clutches go, I used a stock replacement set up in my 70 GS I just converted to a stick. I got it from Falcon. Mark is a great guy and really knows his stuff. The kit was $185 and came with everything, Its butter smooth http://www.falconauto.com/ A quick google search on that Zoom set up revealed its intended for circle track racing and its listed as having a kevlar disc. As Jim mentioned, Im not sure what kind of pedal you'll get with that or what the clutch engagement will be like. Plus Kevlar is a little tricky to break in. On the plus side, it holds up better to abuse
