I had one intake manifold and one set of valve covers powder coated black, NEVER AGAIN
The reason being was the heat retention by the powder coating, both of those parts where on my bracket car and they were horribly hot to touch after a run
I think your "heat" issue was with the color choice, not the technique employed, Black coatings of any kind used on objects that generate heat, radiate heat more effectively in black, however items that don't generate heat painted black, will absorb heat more readily... black coatings in an engine compartment can be a double edge sword when it comes to absorbing or radiating heat
