Whenever I painted a set of valve covers, I never used a primer on them - just the engine paint and they have held up well.

Does anyone here use a primer? If so, what type?

Just curious.

I always spray an engine's bare surface and any of it's components that are going to be painted in Dupont etch primer be it cast iron, steel, aluminum

Yes. I primed my valve covers with a high temp (500 degree) ceramic engine primer before painting them. I think the brand was Dupli-color in a spray can. That was about 5 yrs ago. Its held up well so far.

I have never used primer and have had no issues so far at 10 yrs. No harm to use primer. To me, paint is insulation keeping heat in. Probably negligible.

A thin coat of etching primer on the stamped steel covers is a good idea.

Do any of you paint the insides of the cover?

No. Never. The oil splashing on the inside of them will coat them and keep them from rusting inside.

Yeah, leave the insides raw steel. Paint can flake off as well.

Speaking of valve covers I once had a set of old chromed DC valve covers for a small block and I pulled the baffles out and found large loose pieces of chrome plating just barely hanging on where the baffles were at. Having those fall off and end up in the oiling system would not be great.

Thanks for the replies. I am currently restoring a set and the insides look like they were painted with that rattle can undercoating or something. Never seen anything like it. Been a pain to scrape and blast off. Ugh.

Blasting valve covers is not a good idea !!

A little off topic but I'll fog a light coat of primer on an assembled engine before I paint it. Can't remember the exact number but it's a Krylon primer.

I blast them all the time. Never had a problem. Just make sure they are blown out really well before you paint them/use them.