I also think that Deuce Coupe is onto something. Notice in the first post by JW that the heasition at 18-1900 rpms when cruising are gone. At that engine speed you are on the main metering system instead of idle or off idle system. At cruise with just a slight push on the pedal he may not of opened up the power enrichment system or it heasitated until the power system opened. This could be a too lean condition that was helped with his new exhaust. Maybe a combination of things are at play here. Wapolla, my father was a private pilot and he and I flew in a lot of those planes that Hank mentions. Hank is right about the rpm range and I think he is right about compression also. In the 1960's and early 70's there was 80 octane avagas that was sold at airports and we used. Yes I said 80 octane. Some time in the 70's I think they did away with 80 gas and 100 high lead gas and everyone had to run 100 octane low lead. I remember that this was considered a bad idea for 80 engines because of the higher lead content. I don't know if any engine specs were changed or not to work with 100LL. Probably not because of certification costs. IMHO lead was the best thing ever to happen to gasoline and every effort should be made to get it back in. Jay 6155
