I think he has a 235 chev that would probably have a vacuum advance. If his centrifugal advance isn't working at all the vacuum will retard it even more when the vacuum goes up. He may have a distributor in it that wasn't designed to have a vacuum advance. Distributors for larger trucks didn't have a vacuum advance. Centrifugal only. If you put a vacuum advance on them, and it will fit, they will run like crap.