EDIT: My Dad remembers the car would hardly even run right with the Offenhauser on it. I actually don't think it ever even went to the track with the Offenhauser on it the more I think about it. If I remember correctly it was through the recommendation of those on this site that I switch to the M1. Doing nothing more than switching to the M1 made the car run right which is also when it ran it's best ET when compared to the single plane. That Offy has been sitting on the shelf for years though as has the M1 now. With the addition of kids and a a lack of going racing I put a single plane back on the car for lowered maintenance during street use and down time for the last several years. Think it's worth another comparison before selling it?