Many car owners are content with just keeping their car engines and engine bays clean. However, more meticulous enthusiasts and car restoration fans go a step further with engine painting. So, those who aren't familiar with painting engines might be wondering if enamel paint needs a primer coat. We've done the research to bring you the answer.
Whether you're painting over an engine's bare metal or coating over its old paint, you'll get the best results if you apply a few coats of heat-resistant primer paint.
Would you like to learn more about engine primer coating and the whole engine painting process? Do read on, because we have a lot of tips for you. Without further ado, let's get into it.
Do You Need Primer To Paint An Engine Block?
Enamel automotive paints are some of the best types to use for the engine. Aside from their hard and glossy finish, they also have excellent color retention and high heat resistance.
But if enamel paint is already tough and heat resistant, then do you still need to use a primer?
Some paint manufacturers claim that their newer enamel paints don't need a primer. However, for a great-looking and long-lasting paint finish, the short answer is yes, you need a primer.
A paint finish is only as strong as its primer foundation. Considering the engine's exposure to vibration, heat, chemical fumes, and fluids, you also need a heat-resistant primer for your engine's paint job.
When applied correctly, the primer creates a strong bond with the engine's metal surface and provides greater adhesion and texture for the subsequent color coat.
Without a primer, your enamel paint will struggle to bond firmly with the engine's surfaces, especially with cast iron engine blocks. Even after curing, the enamel paint may shrink or chip off more easily.
However, before you apply any primer or color coat, you need to do a few more steps to prepare your engine surface for painting.
How Do I Prepare My Engine For Painting?
Preparing your engine's surface for painting is probably more complicated and time consuming than the painting job itself. Without proper surface preparation, even the best painting technologies will fail.
Before doing any paint job, you must ensure that the surface to be coated is as clean as possible. Your painting products must stick to the metal itself and not on any loose particles or contaminants.
- Cleaning and degreasing - This involves using mild detergent solutions and degreaser products to remove dirt, grease, and sludge. You may use a brush to help the degreaser. Alternatively, you can try dipping the engine block into a hot tank.
Check out this video on engine block cleaning using a DIY hot tank:
- Rust removal - Depending on the location and severity of rust, you may use a power sander, wire brush, or sandpaper.
- Paint stripping - For best results, your primer should bond with the metal surface. You may use a paint stripper product to help remove any old paint from the engine surface. However, if your previous paint job is still in excellent condition, you may only need to sand the surface for better primer adhesion.
- Cleaning and drying - The previous cleaning steps will leave moisture, chemical residues, metal filings, or other debris on the metal surface. You may use a tack cloth to wipe these contaminants off and let the surface dry completely. For faster drying, some enthusiasts wipe the surface with acetone or pressure dry with an air compressor. Professionals can even heat the surface in an oven or with a gas torch.
Although some new primers contain etching compounds, it won't hurt to do this step separately, especially for smooth, polished surfaces. You may etch using a chemical compound or with a 320- to 400-grit sandpaper or tool.
Whether you use sandpaper or a surface preparation chemical product for etching, you need to clean and dry off the surface again.
After cleaning and etching, you need to cover the engine parts that should not get painted. These parts would include your cylinder bores, crankshaft, timing chain, and many other parts.
Masking may take quite some time and patience. However, you will need to do this to avoid getting paint into parts that are vital to your engine's operation.
After cleaning, sanding, etching, and masking, your engine is now ready for primer application. Make sure you try to apply primer as soon as possible after masking because the surface preparation processes have exposed the metal surface to the elements.
Many modern primer products come in ready-to-use spray cans. Make sure to use a high-heat primer that can withstand high engine operating temperatures. Engines normally operate between 195 to 220 degrees Fahrenheit (87 to 103 degrees Celsius).
Two to three primer coats should be enough for an engine paint job.
How Long Does It Take For Automotive Primer To Dry?
Most primers can dry up after 20 to 60 minutes. Furthermore, some professionals recommend painting the first color coat no longer than 1 hour after the last primer coat.
Although different painting professionals have varying recommendations, you should always read your specific primer product's instructions on the back of the paint container.
Painting The Whole Engine
Some car care purists insist that the only way to paint an engine properly is outside of the car. First, you won't be able to reach, clean, or coat all the engine surfaces that you want to paint. Second, you won't be able to mask off all the parts that should not be painted.
Check out this video on how to prepare and paint an engine outside of the car:
As we saw in the video, the painter cleaned and stripped down the engine to bare metal before applying any of the coats.
Painting Parts Of The Engine
Taking an engine block out of the car indeed seems like the most effective way to paint the engine. However, not many car owners have the tools, resources, and expertise to pull the engine out from under the hood.
Some people may not really be interested in cleaning and painting the lower parts of the engine. Instead, they may just want to paint some top sections to improve their engine bay's appearance.
Check out this video on how you can prepare and paint sections of the engine while the block is still under the hood:
Do You Have To Remove All Old Paint Before Repainting Metal?
Although some painting professionals claim that you don't need to strip away all old paint before a new paint job, you must remove all loose or peeling paint. Furthermore, you need to sand down any good-condition old paint.
Finally, you should still use a primer. Check out this video showing how to paint over a previously-painted engine:
What Happens If I Paint Over Primer Too Soon?
Like with base color coating, you should also wait for the primer to dry in between coats. Color coating over wet primer can give you some bad results:
- The primer may mix with the color coat
- A wet primer coat may peel off
- Your paint may wrinkle or have a flaky and uneven finish
Before applying the color coat, make sure that you follow the drying time stated on your primer product's label.
You may also do a simple check. After waiting about 30 minutes, press a finger on an inconspicuous area of the applied primer. If your finger doesn't leave a dent, then you can spray your next coat.
How Do You Apply Enamel On An Engine?
Before you go crazy with your paint spray, here are a few tips on how to color coat your engine properly:
- Make a few test sprays away from the engine to ensure that your paint sprayer has no build-ups.
- Use long spraying motions for even application.
- Maintain a constant distance between your spray can and the metal surface to be painted.
- Three to four thin coats will produce a better finish than one to two thick coats.
Some enthusiasts prefer to use a brush to apply their primer and color coats on their engines. However, ready-to-use spray cans can be much more convenient for average car owners.
Does Engine Enamel Need Clear Coat?
Some high-heat engine paint jobs can end with enamel color coats as their topcoats. However, for extra heat tolerance, shine, and protection, you may want to apply a high-heat engine enamel clear coat.
Should I Paint My Engine?
Years of abuse from extreme engine heat, fluid and vapor leaks, as well as the elements can take a huge toll on your engine's outer surfaces. At some point, even the most potent cleaning chemicals may not be enough to restore the engine's appearance.
If your engine still runs fine but its outer surfaces have gotten too corroded or blemished, then it might be a good time for an engine paint job.
Some car owners try to give their engines a makeover paint job for engine restoration and rust protection. However, some hardcore car aficionados paint their engines for aesthetic purposes and car show competitions.
Finally, some speedsters do it for a perceived engine performance boost. According to scientific research, black paint radiates heat faster than any other paint color. This means that black paint can help engines run cooler.
If you want your engine's enamel paint job to last longer, then you should apply a few coats of heat-resistant, high-temperature primer before applying the base color coat.
Thank you very much for reading. We hope we were able to help you understand the steps and best practices for painting your engine.
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