QuestionQUESTION: I have a 1967 Chevelle; smallblock; Muncie M21; 11 inch B+B clutch; Hurst Competition Plus; aluminum bellhousing; headers. I wore out the pivot ball under the shift fork mounted in the bell housing a number of years ago in such a way that I can not compare it to a replacement part. As such, I took a best guess and installed one of medium length. Now I eat clutches! In like 15 miles. Local GM dealer offerred me a handful to choose from but I do not know what the original part looked like (ball gone) This has been a obstacle for many years. (I have had the car since 1973) Obviously Chevelles never came with 11 inch flywheels but the setup worked gloriously until the ball wore out. Any help would be phenomenal. Thank you.
ANSWER: disconnect everything from the throw out bearing fork and let it be loose. Then hold it with your hand in the perfect position, measure length of pivot point. Them using whatever, ( a ratchet strap works good) "operate" the fork until the clutch is fully disengaged, but no more. Take a measurement. THIS is the adjustment for your leakage to operate the clutch. For all intense and purposes, the pivot ball height is not critical as long as the adjustment is correct.
What you have done by changing clutch size is eliminate the freedom of leave 1" slop at the top of clutch pedal and calling it good. You probably just got lucking the first time.
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QUESTION: My problem is that I don't know what "the perfect position" is. I cannot visually observe the parts inside of the bell housing. The damage that occurrs to the new plate and disc suggest that the "pivot point" is wrong as the clutch release bearing is not held like it should be (because I have the wrong pivot height). All new clutches either chatter or wear and slip within just a very few miles. It would be nice to cut away the housing to watch its action, however not possible. Simply adjusting the freeplay would probably be right if the pivot ball were in the correct place.
ANSWER: A^2 + B^2 = C^2 even if B is wrong. What I am saying is you can adjust out 'any' pivot ball you get. Since you cannot know which is correct, adjust accordingly for what ever one you have. You are either overranging the clutch when you depress the pedal or not releasing it enough when you let off. That is physics, no other options (if you have the correct parts for the 11".
The ball pivot DOES NOT align anything. That is done by the shaft collar on the trans, which by the way, if it is missing, will do exactly what you have as a problem, but you say EVERYTHING else is correct.
Once again, the perfect position is "just released", as in, jack up the car or remove driveshaft and notice just when tires (or shaft) turn free while depressing clutch slowly. That is the max adjustment length for you linkage.
The relase should be 1" pedal slop. It is that simple.
On one of my 15 1957 Chevs, I ran anywhere from a 3/4" length pivot to 2 1/4 and never trash a single clutch.
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QUESTION: If the pivot ball holds the release fork too high or too low it does not hold the release bearing correctly. Therefore, the bearing does not work properly on the input shaft. THAT is the problem. It seems that it does not work freely on the shaft, causing uneven pressure when depressed and released. If the ball is too long the bearing will hang on the forks ends and/or will not be held completely or at all. Simple physics. If you throw a baseball without the correct grip, where will the ball go? I have extensive mechanical experience also and have built many vehicles. This however, is not something I do alot of as the 4speed is a dying breed it seems.
AnswerI honestly believe your problem is on the shaft collar, not the pivot ball, but you seem to feel differently. I have put probably 15 of these in and have incounter the same situation before. Sorry I could not have resolved your problem, but the ball is in the same spot, vertically and holds the bearing the same on the shaft no matter the length. Fulcrum force is really all that changes and the ablity to "push" the too far in the clutch and that can be adjust out.
Thanks for your interest.
