can someone point me in the direction of a calculator to tell me how much i have to get my gt40p's milled to raise my compression to 10.5:1? vehicle is a 1985 mustang gt.

 

alot more than you can possibly get out of them. A stock bottom end 85 block had 8.5:1 compression on 64cc chambers in the stock heads. gt-40P's will pring you to atleast 9:1, and if you mill them .030, you can get about 9.5:1

 

Cast Iron heads shouldn't be used to support more than 9.5:1 compression. The risk of predetonation is pretty high with iron.

And here's this thing:

http://www.carcraft.com/techarticles...ression_ratio/