Ok, the common knowledge here is that the Omni Power flat valves will raise the compression about .3. But I also read that they decrease the combustion chamber volume by 3 cc. My stock B18C6 compression is 11.1 with the PR3 42.7cc head. Calculating with only 39.7 cc, my compression goes up to 11.8. Now that's a .7 difference not a .3 so obviously one of those two infos is incorrect. Anyone knows which one?