I have a 66 442 with a 455 and M21 4 speed. I recently had my trans out while completing some engine work. I got it all back together and took it out. All was fine for 45 minutes, then I had trouble shifting gears. I was able to get it to shift but it was difficult. I took the trans out along with clutch. Clutch wear seemed uneven and the pressure plate looked rough and had hot spots, the flywheel looked similar. I replaced the pilot bushing, my crank is for auto trans so I used a McLead 8617 (w/extensiion ground down), previously I used the Mondello conversion bearing. I also had the flywheel reground and got a new clutch set (Zoom 30006, disk, throw out bearing and pressure plate).

I put it all back together, adjusted the pedal freeplay (.75-1") and now the clutch will not release. I first found this after starting the car in neutral and was not able to shift into gear. I got back under it and I can see the throw out bearing rests less than 1/8" from the pressure plate splines. when pressing the pedal, most of the freeplay movement is taking out the slop in the linkages and getting the fork firmly set against the ball, there's very little distance before the throw out bearing contacts the splines. With the pedal pushed to the floor, the pressure plate moves but not enough to release the clutch. I tested this by having a helper push the clutch while I tried to turn crank (by hand) with trans in gear. If I tighten the pushrod a little more, the disk releases a little more, to the point where I can turn the crank but there is a drag and only a few thousands gap between disk and flywheel. In this setup ( few extra turns on pushrod), with clutch pedal released and trans in neutral, I can see the throwout bearing turning as I turn the crank, so I'm thinking the pushrod is too tight. The Z-bar has no slop, adjusting it (up/down) had no effect.The clutch pedal moves freely with no slop.

I am wondering if anyone has experienced the same or has ideas on what I need check or what might be wrong. Any help or suggestions would be appreciated.

 

Do you have worn areas where linkages connect to clutch pedal, Z bar and push rod? Little bits of wear here and there can add to your problem. How about Z bar bushing?

 

If you need more adjustment to compensate for linkage wear, there are longer adjustment rods available. https://www.inlinetube.com/products/inl10949

 

I bet you have a bent clutch disc. It’s more common than think. Do you have a stock bell housing? If so, pull the inspection cover and use a feeler gauge to check run out on the disc (between the flywheel and disc) every 90 degrees. Someone will need to be in car pressing the clutch. If you have a blow bell, then, pull it apart. Majority of clutches work with stock linkage and no modifications are needed.

 

Throw-out bearing may be too short.

 

Thanks for the inputs. I hope to be back at it this weekend.

 

Dumb question but did you put the retaining clips back on the throw out bearing. Seen It. Runs ok for while then drops out of place.

 

Is there a specification for the clutch fork pivot ball height for a big block Olds. Perhaps a spec for pivot ball distance to flywheel? I had my flywheel re-ground. I have no idea of the flywheel thickness before the re-ground or how much was taken off or how thick a flywheel is when new. I am wondering if so much material has been removed from flywheel and now the throw out distance is more than it was before.

 

They used one pívot ball in the bell housing regardless if it was a small block or big block. They do make adjustable pivot ball. However, I doubt that is your problem. Look at my previous post.

 

Removing material from the flywheel does not change the position of the pressure plate relative to the surface of the flywheel, so it would not change how much "throw" the throw-out bearing needs to move to release the clutch disc. It would change the amount of adjustment on the pushrod required to move the throw-out bearing movement range back into the clutch's operating range. Your symptoms indicate either a bent clutch disc or some other geometry change in the clutch release mechanism (like an increase between where the pushrod cup is at and the pivot point inside the bell housing).