not to argue with anyone the later shop manuals show more adv timing for hei i believe, not 30 deg though. my rebuilt 250 runs more even more advanced like you stated. i have checked tdc and i don't know why it is but it is right on the balancer mark. i used a sealed power cam. can you set the timing where it runs good even if it shows more advanced?? just wondering. i will follow this thread i have been wondering about mine fore years, it has no hesitation though. good luck i hope you find your answer so i will know as well.