anguswilly
+1y
If you want the paint to stick you'll need to sandblast it. depending on your use you might find the headers last just fine with heat wrap and the under hood temps will drop huge - there is a reason why they use it. Underhood heat causes power loss and can partially negate the HP gains from a header.
Yes it can shorten the life of mild steel headers especially but the benefits outweigh that I think. If you want a real solution, get them ceramic coated.