MG Car Repair: carbon release baring probs, clutch packs, loose bolt

Question

I recent finnished rubilding my 74 mgb, and after 1500 i still have one last problem, it has since rebuild intermitantly screeeeeaammmmed when you put you foot on the clutch, under load(ie when you are moving) and its getting worse, then it goes away then comes back. But this doesnt affect the gear change, Which is fine.

The clutch alingment was checked before it went in. (im told)

Only thing i noticed was that it was installed with the clutch pin jammed against the slaves shoulder on the gearbox, i had to cut it off.

Ive asked around

some say, the new pin from the clutch slave is to long and its pushing the baring into the splines. I did try to shorten it to the point where it couldnt change gear no effect.

I have noticed recently that the car will drive in nutral. and that the rev drop when the clutvh is down is excesive. even with a release bearing. (will stall idle after 30 sec)

it was sugested that maybe its just a loose bolt vibrating at the speed of the engine.

Im gonna have to pull the lump out but dont know what to expect.

Answer
Hi Oliver,
I have installed so many clutch packs and carbon bearings that I have lost count when working in dealerships. About half of them were due to the carbon bearing ware. I don't have a picture in my head from what you said. "it was installed with the clutch pin jammed against the slaves shoulder on the gearbox, i had to cut it off."

Do you mean that after you installed the engine to the gearbox you noticed that the clutch pin (operating rod) was not in the bore of the slave cylinder and it was jammed so hard that you cut the operating rod off? If this was the case, I agree that you need to remove the engine and see what damage the installation had done.

Even though the carbon is running on the metal pad of the pressure plate, the carbon is a lubricant and should not make any noise. While it is true that the carbon does not last unless you take steps to prolong it's life.

The RPM does drop at idle when the clutch pedal is depressed but it should not be any more than 25 to 50 RPM drop. Keep in mind that it is not just the carbon bearing dragging the RPM down, it is the crankshaft thrust bearings also because there is close to 400 lbs forward pressure on the crank when you depress the clutch.

When you get it out, look closely at release arm to see that it is not bent due to the installation and that release bearing is well centered. Anything that can make a loud noise will usually leave marks on something.

Let me know,
Howard