Pistons and cylinder bores

I’d wager the pistons are not bringing measured right. Most pistons are designed for the overbore they are sized for. But some pistons need more wall clearance. KB hypers and some forged want them tight. Like easily within a percentage of error. the solution is buy the pistons, and measure each bore and piston properly. If they need to go bigger have it jones to the right piston to wall clearance and go.

Edit: if you have them a little loose it’s not going to hurt anything. Too tight will.