Hello, I have a 1956 Pontiac that I decided to manual swap. This has turned out to be a lot more complicated than I had been expecting and I have been fighting with the clutch for months! The clutch is solid as a rock and I have been unable to get the clutch fork to move at all. The engine I am using is a 1960 389. The bell housing, clutch fork, and throwout bearing are from a GMC truck (they used Pontiac engines for a while, so they are a good source for manual parts). Manual flywheels for early Pontiac engines are really hard to find, so I am using an aluminum racing flywheel that's drilled for a Ford long style clutch. I was unable to find a clutch linkage, so I ended up fabricating one. When I tested it out it broke before the clutch disengaged, so I assumed the linkage was the issue. I reinforced the linkage and tried again several times until the linkage was finally strong enough that I could push the pedal with all of my strength without it breaking. The clutch fork still wouldn't budge, so I'm convinced the clutch is the problem. I took the transmission off today and discovered that the clutch disk is oriented the right way. I have no idea what the problem could be, really appreciate any ideas! Thank you! -Falcon H
Use a pry bar & a spacer of some sort & try & depress just one finger ( gently) that cwill tell you if its the clutch or the linkage / fork / pivot/ bearing
Did you check the linkage for free/unrestricted movement before you installed the pressure plate? Any chance that something in the linkage is binding when it has to push the throw out bearing? If the linkage checks out it almost has to be in the pressure plate - check it like 2OLD2FAST suggested.
Thank you! I'll try this evening. The linkage moves freely when not bolted to the clutch fork. I don't think it's binding, but it is definitely still suspect. I think I had it in the right way. There was very little play in between the bearing and the arms of the pressure plate. Thank you for the help. everyone!
Is the diameter of the T.O. bearing face correct for the Ford long style clutch release levers? That is, do the contact surfaces of the levers ride roughly in the center of the face of the T.O. bearing. Can you see any "witness marks" on the face of the bearing. It might help to put a bit of blueing on the face of the bearing the next time you try reassembling it. Without the clutch pedal linkage installed, do you have any free-play at all when you try to move the clutch release fork?
It could be that you have your leverage all wrong. You might try putting the throw out bearing in the clutch fork and have someone try to push the pedal down while you observe what's happening inside the bell housing. It should be easy to see with the transmission out.
Do you have one of those alignment tool/shafts to put inside of your Throwout Bearing and see how everything looks. Might have to use a tubular sleeve or spacer to simulate the bearing housing of the trans.
Looking at your picture, the clutch assembly looks strange to me. It looks to me like it's off center to the left. Is that just an illusion? The throw out bearing is hitting on something, preventing it from moving. Just a thought but the GM throw out bearing is not compatible with the fingers on a Long style pressure plate, if memory serves. Are you using A GM bearing and collar? You can get a pressure plate with the Long style bolt pattern and GM type fingers, I believe, from Speedway. If you can't find that one you may have to re-drill your flywheel for a GM bolt pattern. The GM plate has wider stamped steel fingers and maybe a lower profile. Are you using the correct pilot bearing? I may be off my rocker, but didn't GMC stop using Pontiac engines in '59?
....I gotta agree with Glenn , something looks funky in your picture...the bore of the disc seems centered over the pilot bushing as would be necessary for the input shaft to slide in but could the flywheel be drilled off center??.... also I would hook up all of the linkage to the fork and cycle it through its motions without the throw out bearing....
The clutch disk is off center, but I'm pretty sure that happened when I was taking the transmission out. I'll have to look at that pressure plate. It sounds like it might be the fix! Thank you for the help!
The bearing contacts the tips of the arms. It may be a little on the small side (I think) , but it has never slipped through. Also, I tried levering the arms of the pressure plate a few minutes ago. I was able to get one of them to move a little bit, but not very much. I may be able to do better if I can figure out how to get in a better position, or find a pry bar that fits a little better.
What is the spring load of the pressure plate? If you installed a high pressure race style, that could over tax your linkage. I have listed this before but if you haven't read this: throw out arms are a 3-1 ratio. That means if you have a 3000 lb. pressure plate you will need 1000 lbs. of force on the throw out bearing. I believe a normal force on the clutch pedal is 100 lbs of force. So when you look at the ratios involved see if you have adequate mechanical advantage to move the bearing.
I'm using a 347 Pontiac with a BW T85 manual box. This was from a 57 GMC. I've converted the clutch from Z bar to cable. It came without a clutch release bearing and I found out there is a long and a short bearing. This might be your problem I also made my own clutch pedal and gave it a 7:1 ratio. I'm using the standard fork which looks to be about 4:1. Sent from my moto g(8) power using The H.A.M.B. mobile app
If you can move the disc without disengaging the pressure plkate ,you have somneting really messed up. If you can't lever a finger with an 18" pry bar , something is amiss with the flywheel / PP / disc..
Have you turned the engine over with the clutch 'engaged'? The reason I ask..... Is it possible that while bolting the transmission up you are actually (because of miss matched parts) pushing the pressure plate fingers and fully disengaging the clutch. Having the clutch disc move when the trans is removed is making me think that could be happening.
Check the pressure plate . I had one that would not release . broke the linkage twice before pulling the clutch apart. Two springs in the pressure plate had turned sideways no amount of pressure would compress that . new pressure plate ,new linkage. Worked great. Sent from my VS987 using The H.A.M.B. mobile app
Pontiac and 57 GMC call for a 12 inch disk, Not knowing what model of Ford pressure plate you used or Ford pattern pressure plate you used by chance is the disk sticking out past the plate of the pressure plate and binding up on the case of the pressure plate? Basically being pinched on the edges by the pressure plate when you tighten the pressure plate down? If you do have the 12 inch disk and not a smaller one. I checked both Pontiac and GMC and they show 12 inch disks. They show 12 inch Ford Clutches but is your pressure plate the correct diameter for the disk?
Original Pontiac used a diaphram pressure plate, I see you have a Warner type with levers and springs. Possibly the throwout bearing does not function properly with the different pressure plate?
He should have a NATIONAL 1625 Release bearing or one that crosses from that. That is the number for a 57 GMC with a Long style clutch. NATIONAL 614018 is the release bearing for a diaphragm clutch in the same application.
Without the pressure plate on, do the the springs of the disc hit the heads of the flywheel bolts. I use Pontiac flex plate bolts to miss. Also it’s been my experience with a long pressure plate to use the flat face TO bearing. That fork is forged and should never bend. I’ve been using them for many many years.
When you say you made your own clutch linkage what part did you make? Did you mimic a known Pontiac clutch set up? I made my own pedal and linkage set up for my A and found out quickly that there is a ratio that you need to get the clutch to work properly. I had mine screwed up and couldn't depress the clutch at all. After going back and forth on here I was able to get it corrected by redesigning my set up to replicate a stock 47 Ford clutch linkage but only more narrow. Now it works like it should. Now I can depress the pedal with my hand if needed. Just a thought.
For the pressure plate to release, the cover fingers have to be able to move towards the clutch disc about a 1/4" and clear the springs on the clutch disc, and the throw out bearing also needs to clear the disc center hub. The throw out bearing needs to be able to move about 3/4" on the trans output shaft to move the cover fingers that 1/4". The bearing surface must be in contact with the ends of the cover's fingers from after the free play until the disc is released. If there is not sufficient space for these things to happen, you have a component miss match to correct, there isn't a clutch linkage in the world that will be able to release the clutch. In addition to that, when you tighten the cover onto the flywheel, the cover fingers should move towards the disc an amount equal to the thickness of the disc. One thing that bothers me with your picture is how much the dice is offset to the cover, I don't ever remember being able to see the rivets that hold the clutch lining to the disc when or if the disc was off centered. There just wasn't that much clearance between the disc and the center of the cover to move enough to see the rivets. It makes me wonder if the disc your using it too small of diameter. Gene
If the clutch plate moved to one side just by removing the box it sounds like there is no load on the plate by the pressure plate. Something is definitely astray.
Check to see if the release lever is hitting the pressure plate cover. I never ran across a GM engine of that period that had an aluminum flywheel as a stock item (?). Could it be causing a problem? Wrong setback, etc?. Wrong throw out bearing could be the problem ( long vs short). Whatever is keeping it from moving is obviously a solid object and it should leave a mark on something that can give a clue. Sometimes it can be very hard to see. Your bell housing has a removable cover on the bottom so you should be able to see something up there with everything assembled. The throw out bearing should be about 1/8" +/- clear of the throw out fingers with the clutch engaged.
Back in the day when I was doing Clutch job's if I remember right where the Clutch Fork bolts to the Clutch Housing there were 2 different sizes of Studs were the Fork bolted too 1-was a Short bolt & 2- was a long Bolt, there might be a Problem there. Just my 3.5 cents Live Learn & Die a Fool
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