Main Bearing Question

[JDMMA70]

When i removed the old main bearings off my block i noticed a small scratch (catches a fingernail) and was wondering if this would cause the new bearing not to sit right? Or i shouldnt worry about it. Its not a crack either.

Thanks for your time
~jdmma70

 

[Nick M]

What about the crank?

 

[JDMMA70]

What about the crank?

Crankshaft was already removed when i got it. I have another crankshaft from another engine that i planned to use in this one.

 

[jdub]

The good news is there is nothing rotating on that surface. Just take a fine Scott's bright pad and make sure there are no ridges along that scratch.

I assume you will have the crank straightened, balanced and the journals sized/micro polished. Depending on how much material is removed from the crank journals will determine bearing thickness to set the correct clearances. About 0.010" is max that can be removed from the crank journals without having the crank nitrite hardened.

 

[JDMMA70]

The good news is there is nothing rotating on that surface. Just take a fine Scott's bright pad and make sure there are no ridges along that scratch.

I assume you will have the crank straightened, balanced and the journals sized/micro polished. Depending on how much material is removed from the crank journals will determine bearing thickness to set the correct clearances. About 0.010" is max that can be removed from the crank journals without having the crank nitrite hardened.

Alright ill go do that now thanks for the advice.

 

[grimreaper]

looks like some one nicked it with a screw drive or something used to pry with...

 

[Nick M]

I am confused. What about the crankshaft? The old bearing doesn't matter now. The new bearing won't have a problem. Unless you said that is the old bearing when it is the new one.

 

[Poodles]

It's on the surface under the bearing in the block...

 

[Nick M]

Good thing I realized I was looking at the block. :nono:

 

[Suprafast0422]

Is getting the crank straightened, balanced and the journals sized/micro polished mandatory on a small rebuild? I wasnt planning on doing anything to the crank, just stickin ne main bearing in there. Im re-using the pistons/rods and getting the decks machined for a cometic mhg.

 

[jdub]

It is if you want to do it right. At minimum, the journal should be checked, sized if necessary, and polished.

 

[Nick M]

You can have a competent machine shop check it for you.

 

[Doward]

Check it and you'll know. If it's a small rebuild, and within tolerance as far as straightness is concerned, I'd just micropolish the crank. Get your clearances nice and tight for good oil pressure.

 

[nosman4]

I would also have the mains in the block checked to be sure they are straight. If not, you need to have the block line honed. Not sure if this is a big problem with the 7m blocks, but I had it done on my rebuild.