Building a 340

You need to be at least 10.5:1. At least.

To do it with those pistons you have to measure the recess in the head, add in gasket thickness and then do the math and see where you are.

The last 340 I did to get an actual 10.48:1 with those pistons I was .045 out of the hole and an .039 gasket. And that was .045 quench.

If the shop doesnt comprehend that the deck of the piston has to come out of the hole just like Chrysler says, find a better shop.

I’m a firm believer in doing a half inch down fill and doing the math to know the compression ratio because it matters. You can’t guess.