need tips on painting engine

I clean them as good as I can, Put solvent into a paint gun and wash it down several times, then wash it once more to be sure. I spray a coat of DP epoxy primer on the whole thing then cover with 2 coats of Urethane color. Usually Hemi Orange or a IH red that is very close to the original early 273 color. It sticks well on bare metal and all prepped surfaces, only burns off on the heat riser if I use a iron intake and because it is so smooth, makes oil and grime cleanup a breeze. I have had oil pans I painted vatted and heat cleaned and it discolored it but it did not come off completely.