hey i was wondering... when i do my engine to match my old school feel i'm goin for... i was thinkin of welding some rails or somethin to my valve cover for a "finned" valve cover look.
our valve covers are cast aluminum. you can weld to it, but good luck making it look good. if you are going to go that far, just make a one off valve cover. it'll be way cooler.
Good question - valve cover should not get much hotter than the engine coolant which would be less than 200 degrees. Powder coat works great on all engine parts except exhaust and it will handle 400 degrees.
Bondo on a black car works fine in Arizona out in the sun - thats gotta be at least 140 to 150 degrees. I would say give it a try! If you don't mind a painted valve cover it could be a cool mod!