Help! 66 Clutch problem

[Jace66vette]

Hi i was wondering if anyone has come around this problem with their clutch.

I have a 1966 BB which i have restored about 3 years ago, and at that time i wasn't happy with the adjustment of the clutch but used it regardless, well haven't really used it that much maybe 1000 miles. Well i have just been fixing a few oil leaks and I just checked my clutch again and referred it to the book. Now the problem is to get the clutch to fully disengage i have to preload the thrust bearing about half way down the adjustment threads, but if I adjust the nuts to the correct position as per the book which ends up being 2 or 3 threads from the rearward section of the adjustment rod then I cant disengage the clutch. It is like there is not enough throw from the cross bar to disengage it correctly, I have checked the pivot ball and i have the long version, the clutch fork sits 3 to 4 degrees forward. So i think that's right, the only thing i can think of is the bottom lever on the cross bar is not long enough for full clutch travel. Has anyone else ever heard of this?

Thanks

 

[JohnZ]

Corvettes are very sensitive to having the correct mix of components in the clutch linkage in order to be able to adjust it for correct pedal free play (1" to 1-1/4" at the pedal pad, from fully up against the rubber bumper to the point where resistance is felt when depressing the pedal).

The first issue is having the correct throwout bearing; Corvettes use a bent-finger clutch and 1-1/4"-long bearing, and passenger cars use a flat-finger clutch with the 1-7/8"-long bearing. If you have the "long" bearing with a Corvette bent-finger clutch, you won't be able to properly adjust the linkage.

The second issue is the linkage components (pedal pushrod, cross-shaft, and lower fork pushrod). They MUST be combined as shown below in order to be able to adjust the linkage properly.

CORVETTE CLUTCH LINKAGE USAGE



1963-E1966 SMALL-BLOCK:

3832857 Cross-shaft - 135° arm separation, 4.65” and 4.0” hole centers

3819154 Pedal Pushrod – 18” long

3844209 Fork Pushrod – 10-9/16” long (’64-E66)

3739045 Fork Pushrod – ’63-only (integral pin at fork end)

3819152 Pedal Bracket


1965-1966E BIG-BLOCK:

3872962 Cross-shaft - 155° arm separation, 4.65” and 4.0” hole centers

3872961 Pedal Pushrod – 19-1/4” long

3872960 Fork Pushrod – 8-9/16” long

3872963 Pedal Bracket


L1966-1967 ALL:

3888279 Cross-Shaft - 155° Arm Separation, 4-3/4” and 4-1/4” centers

3888213 Pedal Pushrod – 19-1/4” long

3872960 Fork Pushrod – 8-9/16” long

3872963 Pedal Bracket (1966 only)

 

[tracksnblades1]

Is your pressure plate new or rebuilt? Some rebuilders in the past have excessively machined the pressure plates and those assembly's didn't adjust satifactory either. Check the above post for the specs. I don't use remans any more because of the frequency of bad ones.

 

[Jace66vette]

Thanks JohnZ and tracksnblades1 for your advise, Iam currently working away but when i get back i will check all the rod lengths and type of cross bar. But going back through all my paper work i recalled that the clutch was brand new heavy duty setup, but the pressure plate was modified again with a higher spring rate. So iam thinking that the fingers on the pressure plate are flexing to much and not allowing the clutch to disengage correctly, if that's the case i will have to modify the cross bar to give me a longer clutch throw but it the pedal will become stiffer but ill just have to deal with it. Anyway thanks again