Hey everybody! I recently purchased 9.8:1 cp pistons and as I'm waiting for them in the mail I realized that the 9.8:1 is based off of a pr3 head, not a p72 head. I'm planning on running a gt3582, and dailying around 450whp.

Does anybody know what the compression ratio would be with those pistons and a p72 head? And would my power goal still be safe? I do plan on getting dyno tuned from a pretty reputable tuner around me, on 93.

 

This is a helpful compression calculator that should tell you what you're gonna get: https://www.zealautowerks.com/bseries.html

 

I couldn't find dome size anywhere online, so I estimated it to be around 144.25 (as that yielded a 9.8 with the pr3 head) and that gave me an answer of about 10:1 which seems a little lower than I was expecting? Does this sound right, and will it effect my power goal at all or should I just run with it?

 

144 cc for dome? That's a lot. Is it an off the shelf piston from CP? You should be able to find the dish or dome if it is. Or call CP and ask them.

 

A GSR (P72) type combustion chamber typically increases compression by three tenths of a point over a PR3 combustion chamber. I would say you computed correctly.