Nevermind, I just read they are Edelbrock RPM heads. So... if you do have 10.5-1 comp. it would probably not detonate but you may have to back off timing. But like techinspector said the best way to do it is to be positive. Find the formula for compression ratio online. You need to know the piston dome volume, chamber volume, head gasket thickness, etc. You can get all that info from your engine builder.