How To Paint a Race Car Interior | Project LSZ

Tom
Update by Tom Suddard to the Nissan 350Z project car
Dec 23, 2020

Our LS-powered 350Z gets more and more track-ready goodies each installment, all in a quest to build a winning time trials car. Brakes, suspension, weight reduction, power–each factor part of a recipe that should produce an exceedingly fast track car.

Like any complicated project, there’s also a lot to manage here. To prevent duplicating work or forgetting important steps, we like to think of the build as one big flow chart, with each job having prerequisites that must be completed first, and next steps that should be done soon after.

Before this car’s engine swap in the LOJ Conversions shop, for example, we needed to put the LS1 together. Multiply this premise by a thousand individual tasks, and you’ll quickly have your project mapped out.

It’s not an exact science, but our system did make one thing clear: We’re on the homestretch, so it was finally time to paint our 350Z’s interior. No more splotchy red paint, gray primer or rusty roll cage. It’s race car time.

Mounting Electrics, Coolers and More

When it’s time to paint a race car’s interior, it means that you’ve reached an understanding–or at least a stopping point–regarding what will be in the car and how it will all be attached. After lots of imaginary installations on the bench and double-checking the pile of parts we’d ordered, we settled on a final bill of lading for our 350Z.

We’d install the driver seat via the factory mounts, while the Lifeline fire bottle, Moroso oil accumulator and F.A.S.T. driver cooler all needed to be bolted through the trunk floor with nuts and fender washers (so they’ll stay put in a crash). Harness attachments needed to be welded in as well.

The LOJ Conversions wiring harness includes a CAN translator and an auxiliary fuse box, which we’d mount to the firewall with rivet nuts. We’d already mounted our AEM dash to the steering column, while the vehicle dynamics module would be attached to the tunnel with Velcro to isolate the unit from vibration. Our wide-angle rearview mirror would simply clamp onto our cage’s halo bar. To give us an easy source of power for all of our accessories, we’d use more rivet nuts to secure a Rowe Electronics power distribution module next to the CAN translator.

What about our battery? In a nose-heavy car like this one, normally we’d relocate the battery from the engine bay to the cargo hold. However, since our Antigravity lithium battery weighs only a few pounds, adding the copper cable required to move it would more than offset any advantage. We’d just leave it in the factory location.

We also had to make some decisions regarding our wiring harness. After a few attempts at routing and mounting and reconfiguring, we realized that if we moved the factory body control module and fuse box from the driver’s footwell to the top of the transmission tunnel–beneath the windshield–we’d be able to reroute the harness through the center of the car and keep the driver’s footwell and rocker panel wire-free.

Why move the wiring? Because the fewer components the driver can touch (and therefore ruin) on track, the better. Plus, this move will allow our crew to change a fuse while our driver is still belted into the car. It should also help weight distribution slightly, even though we’re only talking about a few pounds here and there.

For now, we’ll leave the entire body harness in place and uncut, which means lots and lots of unused connectors flopping in the breeze. Once we’ve completed a test day and made sure we haven’t forgotten anything–maybe a relay here or an accelerometer required for the computer there–we’ll pull the factory harness back out of the car and chop off all its extraneous connectors.

If all this seems tedious, it is. And even more tedious is this fact: No matter how thoroughly you plan out your race car, you’ll inevitably forget something and end up scratching your fresh paint to add a bracket you overlooked. Our goal was simply to anticipate as many of those things as possible before spraying the car with paint.

Once we’d made our list, we had our to-do items: All that was left to find a home for was our GM E38 PCM, which hadn’t been mounted with anything stronger than zip ties since it departed its ancestral Corvette home. To keep it from whacking us in the head during a crash, we welded homemade brackets to the roll cage at the base of the passenger A-pillar.

While we had the welder out, we also finished our harness installation. We chose a RaceQuip six-point harness for this project, which comes equipped with clips and eye bolts for the bottom four points. After lots of measuring with an angle gauge and a few readings of the instructions, we drilled three holes and welded backing plates and nuts in place on the bottom of the car’s floor pan.

Note that we didn’t technically need to weld in our plates to pass tech, but it’s a stronger attachment and it kept things in place while tightened the eye bolts–no assistant required. There’s no reason NOT to do this if you’ll be painting the car’s interior anyway.

What about the fourth attachment point? The harness eye bolts use the same thread as OEM seat belt mounts, and one of the 350Z’s happened to be in the perfect place. These are plenty strong to hold a race harness. Our shoulder straps (the final two points of our six-point harness) will be wrapped around our cage’s harness bar after paint.

Ignition and Dash

We’d removed the steering column lock and thrown the ignition switch in a drawer weeks earlier, but now we needed a new way to start the car. First step? Wiring diagrams.

We dug into the books and pulled up a diagram of the stock ignition switch. Then, quite frankly, we got lucky: With just one toggle switch and one momentary switch, we’d be able to replicate the stock key’s functions while keeping the OEM fuse protections and still being able to use OEM wiring diagrams to diagnose any problems. Five crimp terminals and a generic “racing use only” switch assembly from the spares box later, our ignition was complete.

Of course, we needed a place to mount our fancy new ignition, and zip-tied to the dash bar isn’t what we had in mind. We also wanted to avoid our past mistakes: It seems as though every single car we’ve ever built has had too small of a switch panel, which means extra switches are inevitably added in a hurry with brackets on brackets on brackets until we eventually get fed up and remake it all from scratch.

How do we avoid that fate again? Simple: Make a larger switch panel. We laid out the ignition panel, fire system button, and Cartek battery shutoff switch on a piece of paper, measured their total footprint, then doubled it. This meant we’d start off with some extra room on our switch panel, then as our car evolves, we’ll be able to easily add more just by drilling extra holes.

A switch panel is no good if the driver can’t reach it, so next we put the seat in the car, jumped inside, and pressed our shoulders in place against the seat back. Then, holding a Sharpie, we marked the limit of what we could reach easily. This is how we figured out that while it might look good to have the fire system button mounted directly on the dash bar, we can’t reach it while belted in unless our switch panel is spaced out toward the driver by 3 inches. We’re happy we figured that out before spraying any paint–or catching on fire on track.

Once we had our size and placement figured out, we bent the panel out of some leftover sheet metal and welded it in place on our cage. Could we have saved a few ounces by welding steel tabs to the bar and bolting an aluminum panel to it? Absolutely, but we decided to use steel for now to keep things simple. We’ll probably cut the steel back to brackets and use engraved aluminum or plastic for panel 2.0 after a season of racing and adding switches.

Let’s Paint

We’d planned our cargo, made our mounts, and welded everything we were going to weld. Finally, we were ready to paint the interior of the car. But that posed yet another question: What color would we paint it?

There aren’t any rules to follow here, so that question comes down to personal preference. And ours is based purely on function over form: We like coatings that are easy to clean, don’t hide dropped bolts and spilled fluids, and don’t distract on track with bright reflections from the interior. Past experience has taught us that battleship grey is a color that accomplishes all of these goals and has the added benefit of complimenting most exterior paint colors nicely.

One last choice: Professional or amateur application? This wasn’t much of a choice for us: Sure, it’s appealing to have a “perfect” spray job done by a real shop, but with enough prep and care, it’s not hard to replicate the results at home if you’re just painting an interior. Since there aren’t any large panels and so much of it will be covered with equipment, nobody will notice if you have a few dry spots or runs in your interior paint. And it’s way cheaper: We probably saved $500 to $1000 by spraying our 350Z at home.

What did we spray it with? Rattle cans, of course. We may be hunting for track records with a larger budget than usual here, but that doesn’t mean we’ve above spray paint when it will get the job done. Spray paint isn’t as durable as a professional two-part urethane, but it’s also less expensive and easier to touch up. For something we’re going to be constantly scratching and scuffing, we prefer paint we can easily respray as necessary.

Before we could spray, though, we had to prep for paint. We removed every last bit of wiring from the car’s interior, then spent a day removing as much seam sealer as we could with a wire brush on an angle grinder. This wasn’t completely necessary, but removing the seam sealer makes it easier to mount things to the car later (no more lumps!) and removes a potential source of fire, too. Plus, it just plain looks better to have clean sheet metal instead of the factory-applied goop.

Once our interior was clean, we masked the entire car with 3M 06724 plastic sheeting. This stuff attracts overspray, and it’s way easier to use than newspaper or garbage bags. It’s also surprisingly affordable: We picked up a 16x400-foot roll online for $35, but you’ll also find it at most professional auto body supply shops.

Is it really necessary to mask off the car like it’s in a scene from “Dexter”? If you want to do a great job, the answer is yes. This is the only way to prevent overspray from landing on your shiny paint, and by masking everything off in advance instead of holding a piece of cardboard behind where you’re spraying like some racers do when painting cages, you’re able to put your full focus into painting.

Once the car was masked, we donned our respirator and went to work: 15 cans of paint later, we’d coated the entire interior from top to bottom in a shiny coat of gray paint. Is it perfect? Absolutely not. But for a $100 paint job, we’re thrilled with how it turned out.

It looked so good, in fact, that Lamin-x, the maker of popular protection films for paint and headlights, sent us a roll of its roll cage film to keep our 350Z looking its best. This high-strength paint protection film comes in a 4-inch-wide roll that’s designed to be stuck on high-wear areas of a cage. We applied a strip to each upper door bar as well as to the dash bar, since we grab it while getting in and out of the car. Time will tell how well it protects, but it’s already survived a week of abuse in the shop without showing any signs of wear.

Project phase complete, we stepped back to admire our work–then got right back to it. The next item on our flowchart is safety gear, and it’s certainly not going to install itself.

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Comments
View comments on the GRM forums
DWNSHFT
DWNSHFT Dork
12/18/20 7:22 p.m.

Yeah, but what's under the car cover?  wink

amg_rx7 (Forum Supporter)
amg_rx7 (Forum Supporter) SuperDork
12/18/20 7:35 p.m.

Jeez that’s a lot of work. I just leave the interiors factory color and go racing. 

efahl
efahl New Reader
12/18/20 8:36 p.m.

I've always painted engine bays and interiors white, so you can find leaks and dropped parts easier.

Honsch
Honsch New Reader
12/19/20 1:36 a.m.

We used Eastwood isocyanate-free epoxy primer with a 2K urethane clear coat for our interior, engine bay, and underside of the car.  It turned out fantastically well and has held up for years.

dxman92
dxman92 Dork
12/19/20 6:44 p.m.

That's a nice looking paint job for spray can.

jstein77
jstein77 UberDork
12/25/20 1:18 p.m.
DWNSHFT said:

Yeah, but what's under the car cover?  wink

Looks like a 1st-gen MR2 to me.

Feedyurhed
Feedyurhed UltraDork
12/25/20 7:28 p.m.

That is one good looking underside. Well done I say.  Wish I had one of those rotisserie thingies.

Tom Suddard
Tom Suddard GRM+ Memberand Director of Marketing & Digital Assets
12/25/20 8:00 p.m.
jstein77 said:
DWNSHFT said:

Yeah, but what's under the car cover?  wink

Looks like a 1st-gen MR2 to me.

Ding ding ding ding ding! 

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