I have a 70 383 we are putting in the kids duster on a budget. I bought a 70 383 motor a few years back that was rebuilt at one time. We put engine in car and had low oil pressure. So engine came out the rebuild must have been a while ago bearings were shot and it has a pretty good ridge at top of cylinders. How much of a over bore can a 383 take? It is .030 now not sure if .040 would clean up. Is .060 safe on a 383.

Only the sonic checker knows for sure. Odds are you could go 0.060 but best to check it. Good news is that 383 blocks are easy to find if you need them. I have a couple of them that I can't give away.......

Thanks Andy. I think I'm going to look for another block if these pistons check out ok they are speed-pro forged.

Make sure and check the ring side clearances before making your final decision
if it has more than .006 on any of the rings think about buyng new pistons.
I use to race a M.W. stocker back when we had to run OEM stock pistons, the top ring lands had .009+ side clearances and the second rings weren't much better. That motor would blow the stock push on breather caps off during the burn out
I should have had them cut for ring spacers to take up the space so the rings would have been kept square to the cylinder wall

I will have them checked at machine shop. I was told to make sure skirts measure ok.

Check that to