Exhaust manifold paint prep

[Mertz]

I’m getting ready to paint my exhaust and intake manifolds and have some silver header paint but not sure if I should use high heat primer. I also read in the archives someone using slipplate graphite spray and baking it. The spray is a lubricant. How would that work?  Should I paint the exhaust black?

[JBNeal]

originally, the manifolds were painted aluminum (silver) from the factory, but those castings were clean.  Rust removal through electrolysis or Evaporust could prepare the metal surface for adequate coating adhesion.  Also, these flatheads were low compression designs so I would be surprised if exhaust manifolds exceeded 500°F.  If your header paint does not require a high heat primer, then stick with the paint instructions to the letter...I have found those instructions are your guide for best coating performance.

[chrysler1941]

I painted mine with aluminum can spray directly on brushed engine parts. 

 

I did not degas engine parts but holds nicely.

 

Coin size flake off occurred after start different places. These are then re-sprayed and blends perfectly.

After 2-3 years flaking has stopped.

 

My advice, pre-heat cast iron parts in oven

[Mertz]

The instructions on the can says may or may not need primer. The guys on the hot rod show tested it with primer and ran the engine retarded to add more heat. Top temp was 946. They worked their way up starting at around 600. I’ll use the primer as Insurance. Seemed to hold up for them during the test but long term is unknown.