well since you never got an answer ill try to help you out, i have personally sanblasted a briggs and stratton 5hp engine, at 120 psi line preassure, works like a charm, cleans it all nice-nice and it doesnt mess up the metal
now iv seen studys on paint vs. engine temp, 2 identical motors fed from 1 fuel tank,1 flat black, 1 chrome and bright chevy orange, the black repels heat way better, and the black motor ran cooler,
that being said, paint wont affect your cooling all that drasticly if used correctly, but i wouldnt go drownding it in paint, nor would i even consider por 15, its way too thick for anything that needs to be air cooled
also powder coating is extremly involved and doesnt need a curing light, it needs an oven, how it works is(if you understand how magnets work) - goes to + ok?
now charge the metal to be coated + , and the "powder" particles- spray on and it sticks magneticly, heat it(i belive 400+ F) and all the particles melt and you have a super hard, perfictly covered peice of metal, that engine atleast around her, would be probibly $100 or more to powdercoat a non metalic color
hope i helped
run it with the paint, shoundnt hurt,
if its an engine,use engine enamel...
simple as that