power steering pump seal blowing out....5 times now

maybe i could run 2 cover washers to take up the space and seat it all the way down? could it be a pump relief valve sticking or a rotor vein sticking?
it is an original 68 saginaw...............there are no scratches or imperfections in the housing that i can see. when he seals blow out they have the metal to metal contact lines like a driven in seal.