I am wondering what the best method of calculating actual compression ratio would be. I have a PR3 head that's been milled .020 and -1.7 dome pistons.

I'm trying to figure out what thickness headgasket I should use if my target compression ratio is 10.5-10.7:1.

I've used the Zeal Autowerks calculator. I realize it has a provision to enter in the .020" that the head has been milled, but does this also account for the actual reduction in size of the combustion chamber from the milling? It's obvious that the combustion chambers' volume would be reduced when the .020" is taken off the surface of the head. Hence, the chamber volume would no longer be 42.7 cc.

This isn't going to be an All Motor build, so don't bash me about my target CR. I just figured the AM forum would be the best place to get a good answer on this question of calculating my static CR.

 

The best way to figure it out is to have the chambers cc'd so you can accurately calculate the ratio. When I was trying to target a specific ratio, I would plane the head 10 thou and then cc it untill I got the chambers to 40cc on my b16a head and that required me to remove .030" off the head. It will vary for people as most heads have larger combustion chambers than the calculators specify.