EDELBROCK PRO FLO 4

they are 1-1/2" hex heads and they wont fit the only ones I can get to thread are the 1-1/4 hex heads but that's only 3 threads in the aluminum heads the ones I ordered from edelbrock are 1-3/4 12 points they wont fit either. I cut one of the 12 points down to 1-1/2 and it still wont thread