No performance effect. It just means that the crank was worn enough that it required machining to smooth and true the journals. When you rebuild an engine it is usually done. Future rebuilds may require it as well. You can turn a crank as much as 30 thou. Bearings have to match it as well and are sold in standard sizes of 10, 20 and 30 under.
That's one of those backasswards things that always threw me. It took me the longest time to grasp that, if a crank was turned .010" undersized, for example, that you order .010" under
bearings even though they're thicker than standard to make up the difference. But, hey, I graduated from a Cal State school so allowances must be made. :lol:
[Modified by The Dude, 1:37 PM 8/1/2002]