What is the comp. ratio?

[FARGO318]

I found a set of Speed Pro pistons, 0.05" deck clearance, 1.637 compression distance. I have a '78 360 block, with what I believe are 66cc heads, correct me if I'm wrong.

Now the problem is, I've read from one person that the compression will be over 9.0, and from another source that the compression will be under 9.0, which is it?

I tried to do the math using other pistons as examples, and came out with 9.02:1, but I don't think thats reliable enough.

How much extra compression will be gained with a thin head gasket and head resurfacing (not mill)

Thanks

[skankweirdall]

The short answer is the volume at BDC divided by the volume at TDC. Take the deck height, rod length, compession height and the crank stroke to figure out were the piston will be at TDC. I don't have the formula in front of me and quite frankly I'm too lazy to look for it right now. It's in the back of the NHRA rule book though if you have one. You can figure gasket volume from that as well. If you don't have it I'll look some time tomorrow. I need to go to bed right now.