C2 Clutch Adjustment

[James W.]

I have a few questions regarding the proper clutch adjustment. I have a late production 1965 Corvette equipped with the L79 engine and 4-speed. It seems to me that when engaging and disengaging the clutch all the engagement and disengagement is happening in the first 1 to 3 inches as I press down on the clutch pedal and last few inches as I release the clutch pedal. When looking at the clutch actuation rod under the hood the bell crank attachment is within the last 3/4 to 1/2 inch at the top (towards the firewall) of the clutch actuation rod. I have the assembly manual, the 1963 shop manual and both the 1964 and 1965 shop manual updates and have read the information and looked at the diagram regarding the adjustment.

What is the best way to adjust the clutch on this car? I find that I have some difficulty getting the car into 3rd gear and downshifting from 4th to 3rd gear when driving the car.

Any suggestions would be greatly appreciated.

Thanks,

James West
Omaha, NE.

[John H.]

Re: C2 Clutch Adjustment

James -

The purpose of the clutch adjustment, as shown in the Assembly Manual and the Shop Manual, is to achieve at least 1" of free play in the pedal between the fully up (against the rubber bumper) position and the point where resistance is felt when depressing the pedal (when the face of the throwout bearing contacts the clutch fingers). The linkage geometry and the amount of wear on the clutch disc determines where the clutch engages in terms of where the pedal is relative to the floor; you adjust for pedal free play, not engagement position - inadequate pedal free play results in a fried throwout bearing.

As the thickness of the clutch disc decreases (wear), the swivel at the top of the bellcrank on the pedal pushrod has to be adjusted rearward (toward the firewall) in order to maintain pedal free play; when you run out of threads on the rod in that direction, it's an indication that the clutch disc is approaching its wear limit (assuming the components are correct).

Adjust the swivel and lock nuts to obtain the 1" minimum of pedal free play, as shown in the manuals.

[James W.]

Re: C2 Clutch Adjustment

John,

Again thanks for the reply. I will adjust to the 1" free play per the manuals.

Thanks,

James West

[Randy S.]

Re: C2 Clutch Adjustment

John,

"As the thickness of the clutch disc decreases (wear), the swivel at the top of the bellcrank on the pedal pushrod has to be adjusted rearward (toward the firewall) in order to maintain pedal free play"

I hope you are correct about the geometry. My swivel is all the way forward (away from firewall) and I assumed it was because my clutch was nearing the end.
Guess I got plenty of disc left

Randy

[John H.]

Re: C2 Clutch Adjustment

Randy -

Yup, as the disc wears, the pressure plate fingers move rearward, which moves the throwout bearing rearward, which moves the outboard end of the (pivoting) clutch fork (and the lower pushrod) forward, which moves the upper (pedal) pushrod rearward, which moves the pedal arm closer to contact with the rubber bumper. To move the pedal arm forward (to achieve correct pedal free play), the swivel must move rearward, thus pulling the pedal arm forward. Rube Goldberg woulda loved it