pesky clutch issue on C3 corvette

[Belgian1979]

Guys,

I have to bother you knowledgeable people again. As some may have read my old clutch started making noise, which made me take everything apart to search for the issue. Not sure what was going on, but in the process I've done the following :
- changed pilot bushing to a real oilite one.
- completely new Mcleod prostreet clutch
- re-aligned the bellhousing to the crank centerline which is now withing .005".
- had to cut some material from the clutch arm opening of the lakewood scatterschield as the short Corvette clutch arm hit the bellhousing on the inside. This then made the arm hit the flange of the bellhousing when the TO bearing was completely against the trans bearing retaining, so I cut small slits in the arm and bend it a little outward to allow for some extra clearance.
- new bearing retainer as the old one was scored and I feared that the TO bearing would hang up on it.

So got everything back together and now I have the following :
- the clutch arm slightly touches the firewall when the pedal is fully depressed. It's not a lot but there is contact
- I had difficulty in setting the 0.05" air gap while at the same time getting the required clearance of .400" on the nuts on the lever coming from the clutch pedal. Somehow when I put in the .400 clearance the clutch doesn't free up. When setting it so that I get at least 0.05" air gap at the clutch plate it is around 1/6-1/4" at the nuts on the lever so the TO bearing is a lot closer to the pressure plate fingers.

Not sure where to go from here.

I was thinking that the pivot in the bellhousing was not correct, but I did set it up. It involved the chevy 4.75" setting (if I remember correctly) while accounting for the block plate and flywheel thickness).
Could it need the pivot to be moved more forward, is so how to go about ? Trial en error ? Because taking out the trans each time to test everything isn't exactly fun.

To note is that the cars does run, clutch fine and the clutch frees up as it is right now.

[sidestep]

Belgian, you are right 4.75 from tip of pivot ball to the block face. Great to hear things are moving in the right direction. I don't have much to offer,but, before you pull the transmission why don't you give this a shot. View figure E in the diagram. This is clutch adjustment procedure from a 55 Chevy.

[sidestep]

And, I apologize but I'm not familiar with the clutch fork, z bar arrangement on a c3, so if this is just not appropriate I apologize.

[sidestep]

Watch the stack height as well. I believe the clutch face side of the flywheel to the mount flange is around .9?for a stock gm sbc flywheel. Also you changed pressure plate and clutch, the finger height may have moved, has the flywheel been surfaced? Last, in regards to your firewall inference, are your motor mounts in good shape?

[bobmc]

throw out bearings with different thickness or height are available, I can still remember a nightmare with a McLeod clutch and a 1965 Corvette

[Belgian1979]

Flywheel was not resurfaced. Motor mounts seem to be in good order. No apparent issues. I think the clutch fork touching the firewall is because of the cramped space in there. Good knows why, but anyway that's were I am now. Not sure how to tackle it.

I also found an explanation on the C3 saying that you should turn the upper not on the rod about 4,5 turns backward from where the TO touches the fingers. That's about where I have it now. Pedal free play seems to be in good order.

Would a thicker TO bearing solve anything in respect of getting a better airgap, while at the same time preventing the arm from touching the firewall and getting the required .400' gap ?

[Belgian1979]

Belgian, you are right 4.75 from tip of pivot ball to the block face. Great to hear things are moving in the right direction. I don't have much to offer,but, before you pull the transmission why don't you give this a shot. View figure E in the diagram. This is clutch adjustment procedure from a 55 Chevy.

Thanks but I have the impression that the rod from the Z-bar to the clutch arm can be adjusted on that car. In mine that one is a fixed length. I can change the rod coming from the pedal in length and this is where I need (according to the manual) the .400' space between the nut and the swivel.

[bobmc]

2 things will move the fork end away from the firewall, moving the pivot ball toward the engine or thicker throw out bearing, obviously you have to be careful to not go over center with the clutch fingers

[Belgian1979]

2 things will move the fork end away from the firewall, moving the pivot ball toward the engine or thicker throw out bearing, obviously you have to be careful to not go over center with the clutch fingers

Hi Bob,

How do you tell if you go over center ?

[bobmc]

crude way is just enough disengagement to be drivable, do you have a hole in the housing to use feeler gauge? the manufacturer should be able to give you the air gap number, in the old days stock type clutches would not re-engage when shifted at high rpm- so called "stuck to the floor"

[sidestep]

crude way is just enough disengagement to be drivable, do you have a hole in the housing to use feeler gauge? the manufacturer should be able to give you the air gap number, in the old days stock type clutches would not re-engage when shifted at high rpm- so called "stuck to the floor"

I had removed an old Borg and Beck type pressure plate for a center force dual friction diaphragm type. Did not add a return spring at the clutch fork thinking the spring under the dash was enough. Went to pull 2nd at about 7200 and the pedal "stuck to the floor". Bob is dead on with the throw out bearings, I would add that depending on type of pressure plate the the throw out bearings contact face should match either flat or round/cone. Also there are two different pivot ball heights, off hand I don't have the figures hit I am sure a Google search or the like would generate a quick answer

Sounds like a neat hot rod, hope you get it sorted

[Belgian1979]

What is the proper release bearing height ? By the judge of the old one and I remember the mcleod being the same size, the new one is 1.220 " heigh.
At Summit I cannot seem to find different heights TO bearings for a 1.375 axle.

So what is the best solution ? A different TO bearing or adjusting the pivot ball ?

[bobmc]

can you access the pivot adjustment hole in the back of the bellhousing with the trans in the car? If you can, try moving the pivot ball, the non adjustable push rod scheme seems odd to my thinking, the clutch manufacturer should be familiar with throw out bearing lengths-very common issue with drag race can type bell housing of different depths and multi disk clutches

[Belgian1979]

I contacted Mcleod but they do not comment on the issue. The only confirmed they have an adjustable unit and that the clutch travel needed is .500" and the airgap needs to be within .050 and .075'.
I cannot reach the pivot ball and btw at the time I tack welded it so it wouldn't move anymore.

[bobmc]

I found this chart for RAM bearings https://www.ramclutches.com/release-bea ... t-bearings the adjustable one from McLeod is probably the better tactic, I never measured air gap back in the day, I don't remember the bellhousing having a suitable hole for feeler gauge, I just adjusted enough clearance to drive the car, it's not that hard with the adjustable length pushrod pushing on the fork