Editor’s Note:Kevin Tetz, creator of the Paintucation video series, is a seasoned automotive painting pro, and today he’s sharing some 101 tips on how to paint an engine bay for best results.
The first place people look at on a car is at the hood—typically a front three-quarter view—getting a feel for the car.
The second most popular view is UNDER the hood to check out the engine. Whether you’re restoring a car, refurbishing it, or a mixture of both as we’re doing on our 1990 Jaguar XJS project (XJ-LS), it really matters how the engine compartment looks.
Granted, it’s hard to keep the oily bits clean with a daily driver, but starting with a strong and great looking foundation is the key to not only a stunning under-hood impression, but to easy maintenance as well.
We decided to go with Summit Racing’s Hot Rod Flat Satin Black topcoat over a bed of black DTM Epoxy Primer for our engine compartment. Even if we weren’t changing the color on this car, spiffing up the engine bay with a satin black finish looks great, and the fact that its catalyzed urethane makes it chemical-resistant and very strong!
Check out the step-by-step methods we used to paint the engine bay of this Jaguar before we swap in an LS engine to replace the out-of-commission 5.3L V12 that it originally housed.
The Jag’s 5.3 V12 was toast, so LS power is replacing it. With the engine out it’s the perfect time to prep the firewall and aprons for new paint.
Time and brake fluid have taken their toll on the factory paint, so a fiber wheel and wire brush gets rid of the scaly rust.
We’ll be using Summit Racing-branded epoxy primer and paint on different areas of the car, so we got a gallon of each as well as all the masking, prep and safety supplies we’ll need.
The original paint gets prepped for epoxy using red scuffing pads (SUM-ABHPMAROON).
The great thing about scuffing pads is that they conform to different surfaces easily. We’re wrapping the pad around a screwdriver to reach into tight areas so our paintjob doesn’t flake later on.
Since we’re dealing with a little scaly rust still in the pits of the metal, POR-15 (POI-45008) is a perfect coating to form a barrier between any rust that’s left over and our new coating.
One coat of POR-15 is enough, and is applied with a disposable brush. Make sure you protect yourself while using this product—it’s impossible to remove from your skin!
Here’s a tip—use plastic when replacing the lid on the POR-15 can. This makes it easy to remove the lid next time you use it.
We’ll pre-clean our surfaces with Summit Racing wax and remover (SUM-UP404G), Tork low-lint wipe towels (TOK-192475-1), and Nitrile gloves (GPN-B46100) to protect our skin. The pump sprayer mists the cleaner onto the surface and is wiped off in one direction with the towels.
With the wax and grease remover wiped down, we’ll use compressed air at about 60 psi to blow any dust and debris out of crevices and cracks.
Masking what we didn’t remove (ABS system and brake lines) is tedious but makes for a clean looking job. You’ll need several rolls of ¾-inch masking tape for this job.
We used a roll of 18-inch masking paper (FSX-18) for the sheet metal and surrounding areas. Don’t use newsprint with urethane and epoxy coatings. Modern paint coatings will bleed through the newsprint.
This is our two-part paint system—epoxy primer for the ground coat and Hot Rod Black Satin urethane paint as the top coat. Every Summit Racing paint product has a TDS sheet that can be printed from the Summit Racing website. These sheets contain everything you need to know about using these products including mix ratios, spray gun selection, preparation guides, drying times, and important safety information.
When we spray we use a well-ventilated shop, a new active charcoal respirator (LMG-08311P), gloves, and safety glasses. Safety is no joke—make sure you’re protected.
Mixing cups give you options and take away the guesswork when mixing paint. Find your correct ratio on the side of the cup and follow it left-to-right for a perfect mix. Your ratio is clearly labeled in the TDS sheet.
The epoxy primer uses a 1:1 mix ratio—equal parts of each component. If your mix ratio is not on the side of the mixing cup, you can do simple math and use the markings to make your ratio. Stir or shake your primer before blending.
I always mix paint products wearing gloves and glasses on as well. We’re adding the equal part of catalyst last.
With both components added, thoroughly blend them together.
Strain the mixed primer into the PPS cup (or your spray gun cup if you’re not using the mixing cup) to make sure you’ve filtered out any debris.
PPS uses a twist-lock top to lock it to the gun. Make sure it’s snapped in.
Run a small amount of material through the gun before you spray! This make sure the fluid chamber of the gun is purged and ready.
A tack cloth (LMG-020003G) is used to do a final surface cleaning before spraying primer or paint.
Test your spray pattern on the masking paper. You should see an elliptical (football) shape for your pattern. We’re using an Iwata LPH400 gun with a 1.4 fluid tip for both primer and paint.
A single wet coat of epoxy is applied using a 50% overlap on each pass, approximately 6 inches from the surface. Overlapping your pattern on each pass gives you an even layer of material without runs or drips.
The masking paper on the fenders allows us to lean over for access while spraying. This engine bay is a challenge to spray with all the different shapes and angles.
The primer’s TDS sheet calls for waiting at least 30 minutes before you can paint over it, but it gives you a 48 hour window where you don’t have to sand it to paint it. This is important with an uneven area like ours that took a long time to properly sand! Epoxy saves you time and allows you to wait overnight to paint if you have to, without doing any more surface prep.
We let our epoxy sit for an hour before topcoating. We cleaned our paint gun with lacquer thinner and started mixing the Hot Rod Flat Satin Black paint. These products tend to settle, so make sure the paint is completely stirred with nothing settled at the bottom of the can.
The paint has a 4:1 mix-ratio—4 parts paint to 1 part catalyst. This ratio is clearly marked on the side of the mixing cup and makes it easy for you to get a perfect mix. Four parts is marked on the far left column, then you move to the next column for the 1 part of catalyst.
A kitchen ladle is an easy way to keep your bench clean while mixing out of a full gallon of paint.
We’re using medium temperature reducer since we’re around 73 degrees in our shop. Summit Racing offers a range of catalyst temperatures to suit whatever your conditions are.
Testing the gun pattern on the paper again tells us we’re ready to paint.
I found it was easiest to start on the firewall and work my way to each apron, alternating from side to side to get even coverage without dry spray.
Here’s why it’s important to have good ventilation as well as good safety equipment. Overspray needs to be cleared out of the shop quickly so the solvents don’t dive back into the coating. Our garage doors were open halfway to create airflow.
We shot two wet coats over the engine bay with 15 minutes of drying time between coats. The Hot Rod Satin Black needs at least 30 minutes before it evens out and takes on its final appearance, so don’t worry if it appears to dry inconsistently at first.
We let everything dry overnight and then carefully unmasked the project. What we’re got now is a beautiful satin-black finish that will be compatible with whatever color we choose for the outside of this project. The coating should last a lifetime and be easy to maintain.