engine paint temp

[gumby]

well i painted the block to keep it clean and keep rust from spreading like herpes in the engine bay. now realizing fireplace paint on the rusty exhaust might not have been such a swift move since i dont know weather it'll radiate heat as well.anyway now im wondering if i should paint the egr valve. the paints rated to 500 degrees. it isnt indicated for exhaust manifolds so im not sure if its alright to use on the egr or if itll just flake off and rust. how hots the exhaust manifold get?