Crankshaft Tolerances

Old 08-07-16, 11:38 AM
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Crankshaft Tolerances

Hopefully someone can clear this up.
My crankshaft is on the bench for my 1986 Ram 50 due to a rolled bearing.
So the tolerances I believe for a new rod-bearing are 1.77106-1.77145. My rod bearings are #1 1.771, #2 1.773, #3 1.771, #4 1.772. This is not something I do very often so I get confused. What I really want to know is if the crankshaft is still good to use without regrinding? The faces are smooth and clean on the crankshaft after I cleaned them up with 400 grit w&d using the old shoelace wrapped around the 400 grit trick.
Old 08-08-16, 03:41 AM
Join Date: May 2006
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Your # 2 and # 4 are out. That's really not by much.

The problem I would look at would be any crank damage done with the rolled bearing. If this is a "last forever truck" I'd regrind it. If you're wanting something to get by for a farm truck, I'd probably get it cleaned up real well and stick it back together. The oil pressure will likely be OK, but you can go to a little heavier oil to compensate.

A lot of guys I know would clean up a crank like you're doing and everything works fine. Some use the 400 grit, but since a lot finer stuff is around now I would go to 1000 or 1500. A big issue is getting the residue grit out of the oil passage for the journal. Make sure you get that cleaned out.

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