Well, .500" is 1/2" so we can rule that out. LOL Honestly, I think somehow your measurement is off on the old pistons. It sounds like maybe your new ones are SIx Pack pistons, which do come up in the hole a good bit compared to stock, so it that information is correct, you could have a static compression ratio of around 9:1 give or take. Have you ever run a compression test? That could tell us for sure what we're dealing with and give a better insight as to what to do about a timing curve.
