The Stovebolt Site Forums The Shop Area Engine Shop GMC 270 crank problems

Some years ago I had a GMC 270 crank out of a CCKW ground -.030/-.030 and stored it until just recently. While getting ready to install it I noticed the rear seal surface is a little pitted. I set it up in my lathe intending to grind the seal surface. (using tool post grinder) I put an indicator on the flywheel flange and the seal surface and got about .001" run-out...looked good. Then I checked the rear main bearing and got about .004" run-out.
My question is...is that too much? Looks like that won't help the rope seal any. The shop that ground it is out of business so no help there.

I could:
1) Dial in the rear main bearing and grind the seal surface to match. I would think the rope seal would be pretty forgiving on size, but this would leave the flywheel running out the .004"
2) Have the whole crank reground to -.040 (expensive option)
3) Do nothing and just put it together.

Has there ever been a rubber seal conversion for the 270?

I'm working on designing a fixture to put a neoprene seal on a GMC block, but it will require some machining on the block and the rear main bearing cap. It looks like the shop that ground the crankshaft made a serious error when centering it in their equipment. The seal surface definitely needs to be concentric with the bearings, even if it's slightly undersize. Have you checked on the indexing of the rod journals? They might also have issues. Best Gasket makes a very good quality rope seal that can handle an undersize seal surface. Do you have a 4 or 6 bolt flywheel flange?

Drop me a PM message- - - -I have a suggestion for a fix that might need to be discussed by phone.
Jerry