Great information! This is like taking a college course. Harvester, you have made my uncles day with your response to timing. He said you are spot on using RPM and vacuum gauge. Also he agrees with Hg per thousand foot reduction. He was a mechanic in WW2 on bombers in the pacific theater and pressure as you stated has a lot to do with the internal combustion engine. I'm ready to learn a new timing method in this I will understand both methods. I will also purchase a vacuum gauge that has a big number face...Thanks, Steve
