Hey, I'm getting ready to buy a Performance bottom end kit from Howell. My question is about the "main bearing size" and the "rod bearing size". I have the option to get standard, 25mm and 50mm. I don't know which to choose. I'm building the block first, and I've got a ported and polished head with a 5-angle valve job that I'm going to build after that, with plans for a turbo this spring. I'm not sure what the significance of the bearing size differences are, so any help or advice would be really appreciated. I want to make sure I do this right. Thanks alot.

Bryan

Is the crank you're using factory sized? Then you need standard.

If you turn the crank journals down .010", you need the .010" oversized bearings. (.25mm)

If you've had it "turned" (aka cut down, or metal machined off the journals to insure roundness and a smooth journal surface) then you're going to need a bearing that accounts for that size. it's actually .25mm and .50mm. One-quarter and one-half millimeter. Same as .010" and .020".

Thanks!