Our Ford NAA is getting a painting update to control rust, bare spots etc. When the valve lifter and rocker arm covers were remover, both showed some rust on the engine side. Was wondering if a couple coats of red oxide primer would hold up on the engine side ? Would hope this might prevent future rust or at least slow it down. Would use Rustoleum red oxide primer with no hardner.
Thank you for any help you can give me.

Paint will fail. Dont do it.

I doubt it would be worth in on a tractor, just clean up the rust and put it back together.

Although, back when I was racing stock cars, on our racing engines we always painted the valley under the intake manifold with a gloss enamel. The idea there was to create a slick surface to let oil drain down faster from the top of the engine to the oil pan. But, that was for an entirely different purpose, and those engines were torn down frequently.

I forgot to mention that working on a old Wisconsin Air Cooled engine prompted my question.
My dear father bought a Bolins Handy Man Garden tractor back in 1962. I still use the tractor. Two years ago the rear main seal went out. In the process of replacing it, I noticed the whole inside of the case was painted with something that looked very much like iron oxide primer. The paint was intact except where it had been machined off for shafts etc. Since the case is cast iron I suspect the painting was to prevent particle of sand from coming loose and getting in the oil. It probably was a special paint or at least specially cured. But it sure held up well. I plan to try the phosphate idea that was suggested.
Once again thank you for your great help.

That's Glyptol and it's there for what you thought. It was actually developed by GE for insulating and sealing electric motor windings.

It was used due to porosity of the cast iron. Paint peeling off the outside due to oil permeation on the underside was not a desired effect.

Many thanks for the replies. They were very helpful.
Thanks again

Clean all the rust you can get manually, paint the outside then soak it in Evaporust. It will not harm the paint. After rinsing and drying wipe the inside with oil.

You would have a terrible time getting paint to stay inside of the motor parts. Little by little the paint would flake off and get into the engine. On new parts which haven't been coated with oil a factory will sometimes put a chemical resistant paint on inside parts but it's baked on. It's certainly better than any rattle can paint you could get. I would just clean the rust off, treat it with phosphoric acid and let it be.

I would not paint the inside of those.

Internal rust is caused by condensation, put in a good thermostat, warm it up and run for at least couple hours regularly and keep oil changed.

Regardless of what you use preparation comes first. You don't want to cover any rust because you will be enhancing its environment and growth, and no paint will stick to rust. flakes of paint coming off inside is worse than doing nothing.

I would never paint the inside of an engine,I would be afraid of peeling paint down the road. Paint chips in the oil pump and plugging the pick up screen.