First the obvious stuff…. Make sure you have all the bracketry , hardware & components attached that you want to paint. Support the engine to allow easy access to all the areas. A lift plate mounted to the carb area on the intake manifold works well because it allows the engine to be lifted up to access the oil pan. Also, on a 4 speed engine, the bellhousing is painted and won’t allow the use of an engine stand.
A spray gun in which a cup liner bag can be used works nice because it allows you to paint at extreme angles and even upside down. If you’re doing an OE type engine where you don’t want a lot of paint under the oil pan, the bag trick isn’t needed…
Various types of paint can be used for engine painting. Aerosol engine enamel will give the poorest long-term durablilty and quality. Acrylic enamel without hardener gives a very original look, however is more easily chipped. For a better, more durable finish, single stage acrylic urethane is the best choice. A correct original look can be obtained with addition of approximately 10-15% flattener additive. Follow the mixture directions for the particular paint manufacturer you choose. Acrylic enamel with a hardener is a good choice as well, but not as durable as the single stage urethane. For the slickest gloss & depth, urethane clear can be used, but it really isn’t a very noticeable difference.
Although some recommend not using a primer and applying the paint directly to metal as the factory did, for the best long-term durability & paint adhesion I’ve found the best method is using a primer. Epoxy primer works well , but I prefer an etching primer such as DuPont Vari-prime or equivalent for the best adhesion.
The most important step is getting the engine clean & oil/grease free. I like to start cleaning with the Zero-Rust Prep Step. It’s a crystal powder mixed with water. This product will remove water-based contaminants that wax & grease removers won’t, as well as oil & grease. This is followed with a wax & grease remover chemical. The best I’ve found for metal cleaning is Glasurit 360-4 Metal Cleaner. Expensive, but it really does an incredible job of cleaning and leaves no residue behind. These products are much easier to handle by applying with a plastic spray bottle. It prevents contaminating the container that can occur if you use the “tip & soak” a rag method. Spray on with the spray bottle and wipe off with a disposable shop towel. Ordinary shop towels are a no-no as they carry oil and other contaminants that can be reintroduced to the object you’re cleaning. For stubborn areas, a scotch-brite scuff pad is helpful to break crud loose. Surface rust can be treated with Picklex20 &/or wire brushed clean. 3M Clean ‘n Strip discs also do a nice job of cleaning up surface rust and are available in various disc styles & shapes.
If your engine has any old paint on it, it’s best to strip it off. An aerosol spray stripper is easiest to handle and will easily remove it. Engines that have been tumble cleaned are ideal to work with, however still must be thoroughly cleaned. They are often treated with a rust inhibitor that can be troublesome if it’s not completely removed.
1. Mask off any openings as needed before starting to clean. 2. Thoroughly clean engine. 3. Blow dry and wipe with a tack rag. 4. Apply primer. One good coat with complete coverage is all that’s needed. 5. Allow recommended dry time. Dust nibs, etc. can be sanded out as needed, but be sure to maintain primer coverage if sanding is extensive. 6. Apply topcoat color. Be sure to apply within the primer’s drying window for recoat. Scuffing the primer on an engine can be difficult! On the first coat I pay particular attention to the easily missed areas first, then apply a more general overall coat. Typically, 2 coats are enough as long as good coverage of all the areas is obtained. On a “fussy” job or area such as the valve covers, the first coat can be allowed to dry enough to scuff out dust nibs, re-tack wiped and given a final coat for a cleaner finish.