How much crankshaft runout is ok?

[eddiep]

Just took delivery of a used high end 4340 forged BBC crank, but the runout is barely under 0.002" (looks to be ~0.0017 or so). Is this acceptable?


Thanks,

Edward

[parsonsj]

No. .0002 is acceptable. .002 is not. Main bearing clearances are typically around .002.



jp

[eddiep]

Thanks JP, pretty much in line with what I thought. It's a Callies Magnum crank and was shipped from someone that didn't put a lot of effort into packing it correctly - I suspect it probably took a few hits during shipping.

Thanks,

Edward

No. .0002 is acceptable. .002 is not. Main bearing clearances are typically around .002.

jp

[Pro Stock]

Just took delivery of a used high end 4340 forged BBC crank, but the runout is barely under 0.002" (looks to be ~0.0017 or so). Is this acceptable?


Thanks,

Edward

Do you mean that the journal is out of round .0018 or that the crankshaft is bent that amount ? if the crank is bent it can easily be straightened, if the journal is out of round fix it by having it ground undersize, do all of the journals when you do this, just the mains or just the rods, you don't have to do both. Better to fix a high $ crank than to throw it away.

Dale