Engine Compartments are often the most abused areas in our vehicles. If you work on your vehicle a lot then you are likely to get chemicals on your paint, scratches from removing and installing parts and because its not an area that everyone else sees it often gets neglected.
Over the time that we or other people have owned the vehicle there may have been a number of color changes and touchups. Often the paint is rattle can dollar store paint that just hides previous attempts to make it look nice but at some point we are going to want to restore the engine compartment to original or at least use some professional paint that we won’t have to touch up every spring.
Here is the problem if someone paints synthetic enamel from a spray paint can in the engine compartment to change the color and you go right in with some urethane or acrylic enamel professional paint it will start wrinkling up like the texture on your valve cover.
What you want to do is test the paint for type and then decide if you need to put primer on it before you base coat it.
The way you test for synthetic enamel is by taking a few paper towels and moistening them with paint reducer.. don’t use a lot just enough to get them moist.
If you scrub the paint with the towels and it comes off then you need to use primer.
since engine compartments are difficult to work in with all the tight places and complex areas .. meaning its not a flat hood then it is probably best to use primer sealer on the surface to give you a fresh barrier between the synthetic garbage paint and the good paint you will be putting on it.
As long as the paint is in good condition you can scuff it with a gray scotch brite pad you can get at the paint store.
Then put primer sealer on it that does not need to be sanded.
Let the primer cure and then you can paint your basecoat or single stage paint over it.
Primer surfacer will require sanding before you paint it that is why i suggest primer sealer which does not require sanding unless you let it sit for over 8 hrs.
I do not suggest an epoxy primer that stuff pretty much sucks for any area you want to look good .. its just too much to deal with. If you had a ton of rust maybe but i don’t even like it then for any area that is going to show.
So .. test it.. if it comes off real easy then primer seal it.. give it the recommended flash time and then start painting.. if you get a run you can cure and sand it lightly .. if you take more then about 8hrs before you start painting color let it cure overnight and scuff the surface before you start applying color.