I appreciate your interest...I understand that compression ratio is a value that needs to be factored in when determining the application of a camshaft...Suffice it to say that the pistons are advertised as .030-over replacements for the 383 HP engine...I do not know what the EXACT compression ratio is, and I frankly don't care. I would assume that it is close to what was advertised...that's good enough for me. This is not a race engine. I just wanted to hear of fellow hobbyists experiences with the cams in the subject line. Thanks