I just picked up my heads from the machine shop. Although they offered to prime them, I declined the offer, preferring to paint them myself. The heads looked clean, felt clean, so I went ahead and applied the primer. Within a half hour, the primer began to peel. I had used the same primer numerous times before (more on that later) without a problem, so I concluded that they must have been residue on the heads.

Fortunately, I was able to remove 95+% of the primer by using a brass wire wheel; brushing on Goof Off took care of the rest. I then used several applications of 91% Isopropyl Alcohol to remove any remaining residue. I primed the head (fortunately I'm doing one head at a time) with success. I'll apply Ford Red tomorrow.

Seymour's PBE Professional Primer is the best rattle-can primer I've ever used and will use no other. It doesn't run/splatter, dries quickly (can be sanded/top-coated after 15 minutes), and the spray pattern can be adjusted horizontally/vertically, if needed. I also use Seymour's Ford/Chrysler Red because Gil Baumgartner (CTCI Gil's Garage) said it was the closest match to the original Ford Red.

Save yourself a lot of trouble by making sure there's no residue on your engine parts before you paint them.