Inliners International Forums General Discussion Engines 261 crank

I had a rear main oil leak in a completely redone 261 (900 miles on since done). Pulled rear cap and bearing was worn. Machine shop has looked and says "the crank has been pushed forward" causing the brg wear, then leak. Used Langdons asbestos rope seals.

They think it could be a clutch set too tight, as if "riding the clutch", but I know the throwout brg was not tight against the clutch.

The trans is a M20 - I'll check to make sure it is not the cause, ie the input shaft is not 'long', otherwise ???

I never thought about it before, but I guess each time the clutch is pressed it puts forward pressure on flywheel/crank. Is there anything that should be taking this pressure?

It sounds like your thrust bearing has too much clearance allowing the crank to move back and forth. When the crank is reground for a rebuild the crank grinder should set the clearances for the new bearings on #3 main thrust surfaces to .002-.003 inch (or whatever the specs call for). Check with your machine shop.

You would have been aware of that long before 900 miles had accumulated. Initially the trans probably would'n sit tight against the bellhousing. Secondly, if the input shaft was tight against either the pilot bushing or the nose of the input tight against the back of the crank you would have had felt like there was clutch release problems. The pressure on the input shaft would have kept it spinning even though the clutch pedal was fully depressed.

What pressure plate are you using? I expect if it is an extra heavy one you would have mentioned it, but I have to ask.

I'll second the extra thrust bearing clearance as a possibility. If the bearing wore that much in 900 miles, what does the crank look like?

At this point you probably want to have the shaft checked for straight as well.

If the thrust bearing didn't have excess play when you put it together it does now,and if the input was too long there will be evidence of wear and metal shavings. If that was the problem you would have heard and felt it. How much can you move the crank now? Were you careful when installing the damper?

Sounds fishy to me. I have a truck engine with 20 thousands of end play and the fillet/radius of the crank still hasn't contacted any of the the main bearings.

Sorry about the multiple posts.

Got the motor back from shop yesterday - still not clear why the end play problem. Trans input shaft length OK.

They checked crank - fine, re-polished rear journals & rear seal area - felt the Langdon seals I was to use was much too stiff - they used a stock replacement that is much more flexible. Put motor in truck today - will have all bits re-attached & started soon.