I know I am asking questions and not answering your's, but I am just trying to get a better handle on the problem. I assume you are sure the cam is in straight up and not off? What carb and distributor are you running? I asked about the rpm wondering about the converter, but if the set up is not new then you did not have this problem before. I had a car that would not spin the tires at all, but upon accerleration it would come alive about 2800 rpm (problem was wrong converter).