questions on 850 engine rebuild

tripper225 · Sep 21, 2021

I got a engine overhaul kit from yesterdays tractor. The crank main bearings for .01 under are not the same size. The front and rear bearings are .002 larger than the crank installed in the block. The center main is .003 larger than the crank installed in the block.

The manual calls for .0007 to .0023 oil clearance for all three mains.

Two questions.

Is it correct to have more clearance in the center main to lubricate the thrust surfaces?

Is it correct to have the clearances toward the high side of the factory spec?

Thanks in advance for your assistance in this project.
Jim

Bern · Sep 21, 2021

While it's technically out of spec, myself personally I would not sweat being half a thou off. I'm not sure what you're using to make the
measurements, but half a thou is getting near the point of questionable accuracy for most people. And no, the center (thrust) main is not
designed to run with more clearance. If it was, the factory would have said so.

Fritz Maurer · Sep 21, 2021

Has the crank been turned or are you doing a roll-in
or what? If you are checking with plasti-gage, you
need to hold the crankshaft up in the block with a
jack if youre doing it from underneath.

questions on 850 engine rebuild

tripper225

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Bern

Well-known Member

Fritz Maurer

Well-known Member

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