[MDGOAT69]

I have a 1971 455 that came in my 79 Trans Am that I am really wanting to run next season. *Please understand that I know this is less than ideal, my plan is to pick up another engine to build properly, but I want to drive this car next season and sending this engine to a machine shop for a proper inspection and new rotating assembly just about guarantees that won’t happen.*

The engine is a previous rebuild that has never been run. I pulled the 66 heads off and I confirmed that to be true. Now for the sad part. It’s bored .060 and the pistons in it are the Sealed Power NP417s, with the valve reliefs and the beveled edge (YUCK). Rods and crank appear stock.

Before I found out about the pistons I picked up a set of 6X-4 heads to swap on and was hoping for 9.3-9.5 compression and a nice fun engine with a RAIV cam swapped in. Now that I know I have these pistons, I know that CR ain’t happening.

So the big question is this, now that I know about the pistons; I know the CR is getting killed with the beveled edge. My question is how do I figure out how low this is going to drop my compression?