Got a big Block Chevy block,it’s got 7.4 on side of block how much can I bore the block

0.060". I pushed one to 0.070" but the walls start getting a little thin. I gave up on OEM blocks. Went with a Dart 4.6 block and punched it out to 4.625 and still have 0.300" thick cylinder walls.

Casting number?
I have a handful of Gen 6's that I sonic checked. At standard bore, not a one was less than .210. I've seen older Mark IV's that couldn't safely go more than .030.

Magnafluxing and sonic testing are only expensive if you fail to use them.

I've had great luck with oem blocks but I always keep the bore to a minimum. I sonic test all my blocks and always use the thicker ones for the good stuff. Only way to safely tell how far you can go is to sonic test but .030 is rarely a problem.

We push ours to .070 4.320 and most are at 4.310 with no issues. We do use Embecco cast iron grout block fill but I don’t believe it’s helping the power or the bores. This new combo we have had no filler. If you can swing it buy a dart block. That’s our next build. Stable blocks are worth power.