In this howto we will paint the firewall and engine compartment with your engine in and match it to its original paint color or a new color if you are doing an overall paint job.
There are times when you need to paint your car’s engine compartment and doing so shouldn’t mean pulling the engine and a lot of hassle.
I have seen over zealot car builders get bent out of shape about painting their engine compartment so much so that they divert time from other jobs. They think they need to have the inside look as nice as the outside and go as far as wet sanding with 3000 grit and buffing the finish as if they are building a quarter million dollar Ferrari and not a daily driver that they want to show off to their friends.
The fact is you don’t need to go through all of this hassle to get a factory or even custom finish in your engine compartment.
The first step to a good paint finish is cleaning
The first thing that you need to do is clean … clean and clean again all of the surfaces in your engine compartment.
When I get a car that I am going to do an Overall color change on the first thing I do is wash it from top to bottom .. inside and out.
The choice to do the engine compartment first or the body first is really up to you but I normally start by doing the door jams then the body and then a day or two later the engine and any touchups.
Unfortunately when you paint this way everything needs to be clean and kept clean through the whole process. I say unfortunately because that means once the car is clean you really need to maintain it and not use it until you are finished. This can take a full week to complete an overall color change but if you do it right it should last many years.
Degreasing your engine is the first part of cleaning you want to complete it prior to performing any bodywork on your car.
A second wash should be completed after you finish your bodywork but before you prime the car for paint. At that point your engine compartment should be clean enough to paint.
If you are simply painting the engine compartment then I suggest that you clean it twice over 2 days that way it will have time to dry and you will be able to see any spots you missed.
It should also be said that if you are going to detail your engine you want to do that between the first and second washing of the engine compartment you do not want to come back after you have painted and try to remove valve covers or scrub down aluminum throttle bodies with wire brushes. AND you can not use reducer or solvents in your engine compartment for at least 2 to 3 weeks or you will melt the finish… not completely but just enough to make it look bad.
Preparing for Paint
Masking everything will be the hardest part. It takes time to mask off all of your wires and accessories but an easy way to get this done quickly is to use kitchen plastic wrap.
Don’t skimp and get a cheap brand of plastic wrap you want it strong enough that sharp edges wont puncture it and so you can pull it tight and it won’t release on you.
Wires and hoses can be wrapped loosely in plastic you do not want to have to cut it off with a razor blade so wrap it loose.
Smaller areas can be masked with paper and tape.
Make your final scrub down with reducer on a clean rag. This will slightly etch or melt the original finish enough to get a bite without the need for sanding. I usually order a pint just for cleaning all the jams and engine compartment.
Painting the Engine Compartment
Just like any other paint job you need to start with the surfaces that are farthest from you and hardest to get at.
The hardest parts will be the lower firewall behind the engine and then the area around your steering box and break power booster.
You want to paint under things and into any access areas first and then complete the job by working up the side of the firewall to the top of the engine compartment.
Make sure the lower areas have a good two full coats before completing the higher areas.
For difficult places you can use an air brush to get your hand into tight places.
I normally use a touch-up gun or an air brush for a lot of the lower work.
If you have used a single stage enamel with a hardener then your work is done when it looks ok.
Normally I come back the second day with my air brush and hit any areas that need it after the tape is removed.
An air brush can flood a pretty large area (maybe an inch or wider) if you open it all the way or it can hit fine lines if you close it up.
Final Note
Now some guys are going to say .. man think of all the taping its going to take hours to get everything right.. well yea it might if you are not very skilled at taping.. but then again think of how long it takes to pull an engine and put it back in and get all of that right.
Sure you can pull your engine in a garage in a day and maybe maybe you will come out with a slightly better finish. But if you take your time and give all the surfaces at least three full wet coats you will do just fine with the engine in.
Some people ask about clear coats.
This is not a bad thing if you have some clear around from your overall that you can spare but the fact is you don’t really need it if you put the proper amount of hardener in your paint and then let it cure for a couple weeks before you go in and try to clean your valves off by pumping 5 cans of gumout down the throttle body.