FE bore job - need the pistons first?

[ajsmolik]

The machinist asked me for the pistons to ensure proper clearance. I told him I wanted 0.030 over, but didn't have the pistons yet because I wanted to be sure I didn't need more bore than that.
He said some pistons allow 0.0015 and some up to 0.002 and it's better to measure first to make a tight fit. I told him to assume a 0.0015.
Is this a big deal? I thought most guys waited until they got the block back before deciding which ones to get.

[DuckRyder]

Yep, you need the pistons to do it right.

They need to be measured to ensure proper clearance, or in the case of skirt coated speed pros, you will get an exact measurement to finish the bore too.

Your machinist should be able to give you an idea if .30 over will clean it up.

[FORDification]

I agree....a GOOD machinist will actually fit each individual piston to the cylinder, in case there are very minor manufacturing differences in diameter, especially between different manufacturers. You'll have to find out from your machinist if your block needs to be bored out, and if he says it does need a .030 overbore, then get the .030 pistons and give those to him so that each cylinder will be bored/honed to the exact tolerances required by each individual piston.