I have 2 cranks here from my boat engines, both had main bearing failure, cranks are fine but need machined to clean them up.

one is .010 now 150.00

one is .040 now 80.00 should be fine in a lower HP engine.

I had my crank cut .010 15 hrs later spun #3 bearing,complete rebuild again.Think I should put a new crank in there,it is a 502.I had it built by a good builder.Line bore balance,every thing.good oil temp,240 tops.lost 20 psi full throttle 5300 rpm.whats your feeling,thoughts.Thanks

It is not supposed to matter until you are at .030 or so, I was told the more power you make the more likely an issue will occur, I put 2 new cranks, rebalanced both assemblys, ran HV/HP oil pumps, I have 20 hrs now with not a hint of issues, I make about 430-450 hp.

If I was doing it buy a new crank.....run the 1-4 mains at .003 and rear at .0035 you should be fine, rule is .001 per 1" of journal, rear is wider, that is why you want more on the rear.

Thanks for the advice.The builder is trying to say I have preignition.The pistons (all) are coated with carbon,no burns,no scuffing,plugs look fine.It seems to be on the rich side (safe) in what I have learned.He said the head looks like it is trying to lift off the block.Carbon under the head gasket?The main cap was not straight any more.Need to replace it and line bore.I will keep you posted.

You will not wipe mains due to preignition, rods maybe but not mains, what was you oil pressure/temps? at idle cold/hot and at throttle cold/.hot? I doubt the heads are trying to lift, that takes alot of problems, what hp is it? stock? these heads have ALOT of bolts holding them down.

I have hi-volume pumps 70-80 psi start up.Hot 5200 rpm 40psi 240' F.It is a 509 (.30) over 502 JE pistons HP intake EMI Headers thunder.Square port heads.Set up like the HP 500.800 cfm Holley.# 3 main spun after about less then 20 hrs.Running wide open for about a 2min,oil pressure dropped to 20psi!!!!!