Originally posted by 4ontheFloor:
Use a thin coat of radiator paint on the outside or nothing at all.
I agree standard engine paints are too thick for this use because they can interfere with heat transfer. Eastwood has a "Radiator Black" that withstands 300ºF. As they put it, 'it sprays on thick enough to cover completely, yet thin enough to not interfere with heat transfer.'
Thay also sell a brake drum coating for this exact purpose.
