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MG MGB Technical - MGB clutch noise

I have installed a refurbished engine into my MGB. The clutch was not changed as it was OK. I now have a really bad grating sound when I depress the clutch which gets worse if you select a gear. It occurs on any gear selected, but doesn't happen when changing gear on the move. This noise was not apparent prior to dismantling.
Can anyone suggest what might be the problem? It doesn't sound like a thrust bearing, and it is intermittent. I'm trying to get an idea before I go back to the garage that rebuilt the engine & gearbox unit.
J Reckitt

I'm no expert on MGB clutches. but having read Paul Hunt's chapter on clutches and particularly on release bearings, I did wonder whether you have a roller bearing fitted rather than a graphite bearing? It would seem they can be noisier than graphite.

http://www.mgb-stuff.org.uk/clutchtext.htm

Also according to John Twist roller bearings are not recommended.

https://www.youtube.com/watch?v=4KIdkOWVcGg&feature=youtu.be
Andy Robinson

Thinking out loud.

Before depressing the clutch the gearbox internals would be spinning, to stop when the pedal is depressed - in theory. A noise as you press the pedal, ow while it is half fully or partly down, is more likely to be release bearing/cover plate, particularly if there is any vibration up through the pedal. I can't really see that being gearbox

If there is grinding rather than a 'simple' crunch as you engage reverse then it means the internals are still spinning, but that should only result in baulking for 1st to 4th.

However if there is vibration up through the gear lever then it sounds more like a gearbox problem, in which case maybe two problems.

On the one hand unless you know the clutch and bearing has only done a few k then it's false economy not to change it. But on the other there have been a spate of graphite release bearing failures and even a cover plate failure recently, as well as the problems of using a roller bearing unless it has very good concentricity with the first-motion shaft. JTs explanation of why rollers are not good doesn't really hold water as in practice the alignment only changes fractionally between fully in and fully out and not the huge travel he shows. It's the alignment as it starts to take the load of the clutch that is important.

With a roller as standard in the V8 and having had one in the 4-cylinder they are not inherently noisier - until they start to break up!
paulh4

I have a graphite release bearing which I think is breaking up due to the clutch components being replaced in a different position to the one it was originally in. I have decided that the first step is to remove the engine (again!) and replace the clutch. The question is whether to replace with a graphite bearing again, or go for a roller bearing. I have heard that roller bearings can cause trouble?
J Reckitt

See above! If the concentricity is good you may be OK.
paulh4

I have now replaced the clutch with a roller bearing thrust. No more screeching noise!
J Reckitt

Did you lubricate the crankshaft pilot bearing? Have put pictures on my blog at https://mymgbinfo.wordpress.com/2019/02/20/oiling-crankshaft-pivot-bearings/
This can be a source of screatching noises.
But sounds like you've sorted it.
steve livesley

This thread was discussed between 04/02/2019 and 06/03/2019

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