I bought a 75k mile shortblock and started by pulling the rod and pistons. The rod bearings looked great except for # 6 and 7. The crank mains look and feel fine. I planned on installing new bearings and rings and reassembling it, before I found this. What would you recommend?

I'll go snap a pic of the crank...

 

This is # 7 and 8. You can see some discoloration on 7, but you can't feel anything. Should I worry about it, or try to have it polished out?

 

#6 has a similar situation going on. Looks visibly scratched but feels smooth.

 

I'd mic up the crank, check the journals for size and also see if there's any excessive taper or o-o-R. If it looks alright, get the crank polished and run new bearings throughout.

One thing I'd make sure to do is to check your clearances during reassembly - it's a gamble throwing an engine back together without doing that. Sure it takes longer but it'll save you lots of work and $$$ in the long run.

 

You're exactly the person I'd hoped would chime in, thanks. I've been following your build thread. I've got a basic 8" mic and tons of pastiguage. Other than that I'll need to rely on a machine shop. The pastiguage won't help me find out of round or taper, but I'm not sure if a straight mic will help much either.

I know they make bearings in .001 looser size, but do they make them in .001 tighter? I'm worried that polishing the crank may loosen up my clearances.

Anyone know of an excellent machinist in south Florida?

 

So far I'm leaning towards Mike at TOtal Engine Concepts. Comments?

 

If it were me I'd have it turned .010/.010 just for GP since that's something cheap to do and run oversized bearings.

 

Spoke with Mike at TEC and he seems to be fairly confident, without seeing the crank, that it should'nt need to be turned. He suggest to go 3.905 with aftermarket rods and pistons, but that's not in my budget. I explained that i am a cheap bastard and wanted to just throw bearings and rings at it. We agreed on it at least getting a fresh finish hone on the cylinders, crank polished, rod big end checked and very lightly honed if needed, hot tank and wash for $250.

I think that's money we'll spent, and I'm glad it will be in the hands of someone with ls specific experience.

 

I got rod knock and rebuilt my bottom end.
got crank turned at machine shop, and they got me the new matching bearing. Everything went in perfect. They took out the guesswork