High temp engine enamel. $7 a can at the local auto parts store. I sand blasted the valve cover, masked off all the areas I didn't want paint to be, and applied about 10 LIGHT coats.

It's been about 8 months, and the heat hasn't got to it. The side by the timing cover is scratched off though. I was replacing a belt, and had to move the power steering pump, and the valve cover was the only thing is would rest on.