Updated March 2020 - It's a lot of work, it's kind of inconvenient, and if done incorrectly can be downright dangerous - but lawdalmighty, when executed correctly, can send your project build to the next level of lust-worthiness. Originally published in 2016, take a gander at your updated guide to a proper shaved and tucked engine bay.
Smoothing out the sheet metal around your engine and ditching or tucking away all kinds of bits that you don't want seeing the light of day won't make you go any faster. It also won't make your car any safer, it won't let it pass an emissions test any easier, and it's on the top of your to-do list this side of an unreasonable ride height and rims that cost more than your whole Civic. Execute things right, though, and a properly shaved and tucked engine bay can make whatever trade-offs you've had to make entirely worth it.
A History Lesson
Know that the 17-year-old with the dumped Integra on Instagram didn't invent the whole idea of a shaved and tucked engine bay and you already know half the story. Carburetor-era hot rodders like your grandpappy have been smoothing out firewalls and concealing things like brake lines since the days when street racing was a wrist-slapping offense and the thought of mandatory smog checks was about as likely as men walking around with hair buns. It's the VW and Honda masses who've turned their engine bays into blank canvases, though, and as it turns out, there's a whole lot more to doing it right than you think.
Getting It Done
A shaved and tucked bay isn't an all-or-nothing proposition. Smooth out that firewall and stow away that wiring harness but leave that power steering pump and those brake lines alone. Or tuck it all away and get rid of every bit of nonsense the guy who designed your car thought you needed but is too big of an eyesore for you. There's no right or wrong plan, but there are all kinds of wrong ways of going about doing it. Read on and shave and tuck your engine bay the right way.
The Body: You're in for a whole lot of bodywork, so if you've ever thought about painting the outside of that ratty 240 of yours, now's the time to do it. Shaving that engine bay starts with removing the engine and just about everything else from under the hood. And by everything else, we mean every bolt, bracket, and line you see.
Get yourself a pneumatic air grinder, stick a wire brush on the end of it, and cancel your Netflix and chill because you'll be stuck removing whatever seam sealant you can find for the next several hours. Whoever made your car applied that sealant to just about anything that was welded or butted together underneath your hood to prevent corrosion and keep paint from cracking, but sealant's ugly and the ugly's got to go.
The shaved part of that shaved engine bay starts with you figuring out which bolt holes and openings throughout your firewall, shock towers, and frame rails can be closed up. Plan on relocating that brake proportioning valve someplace else, for instance? Might as well say goodbye to those mounting holes. You'll need basic fab skills to go any further, though. Here, you'll be cutting sheet metal to fit those holes and welding them into place before assuming body shop duties. Phoenix-based engine bay expert RC Chacon of RC's Garage says that prepping the metal properly is key. Here, any paint near whatever hole you'll be welding up's got to be thoroughly removed.
Finished? Grab that air grinder, swap that wire brush for a cutoff wheel, and smooth out those booger welds you just gobbed into place. Apply a thin layer of body filler throughout the bay before sanding it all down to a smooth finish. According to Downstar Inc. 's Frank Garcia, who's got one of the most recognized Honda engine bays in the country, the less body filler you use, the better. That seam sealant you just got rid of helped absorb vibrations and flex that occurs in the chassis where sheet metal joints are butted or welded together; without it and with too much body filler, the chances of your paint not cracking are about as likely as man-buns being a good idea. Chacon follows a different approach, applying self-leveling seam sealer throughout the bay for a smoother look.
The Electrical: There are as many ways to tuck away that wiring and those electrical bits underneath your hood as there are hacks who've got no business using a soldering iron. It starts with relocating that battery and under-hood fuse box someplace you'll never see them, like in the trunk or, in the case of the fuse box, under the dash. When relocating that battery to the rear, Chacon says to make sure it's still accessible and to not skimp on wiring thickness. "A lot of people use the wrong gauge wiring when relocating the battery," he says. "I like to use a minimum of two-gauge for power and ground."
For everything else, you'll need to cut, splice, and lengthen every wire, but if you're slightly more sophisticated you'll de-pin them all from their connectors and replace them with longer, splice-free sections. And don't even think about using butt connectors. Garcia says that no matter which method you use, you'd better label every connector and every wire before disconnecting a thing or, better yet, modify one wire at time to avoid mixing everything up. Plan on routing that harness inside that frame rail? Good luck diagnosing that next electrical short that'll happen about two days from now.
The Brakes: Your car's brake booster works in tandem with your car's master cylinder, allowing you to slow down and stop that 3,000-lb. sled of yours. Ditch that booster and your brakes'll still work, but those chicken legs of yours will have to work a whole lot harder to make it all happen. Get even more serious by relocating that proportioning valve and whatever brake lines normally run past your firewall underneath your dash. Here, the right fittings and you knowing how to properly bend and double flare those custom brake lines you're about to make can mean the difference between success or your car not stopping when you need it to. Or follow Chacon's advice and get yourself a pre-made kit made up of flexible lines. "If flaring lines is a must, though," he says, "prepping the line properly is [critical] to a good flare." Chacon says perfectly straight cuts and properly de-burring them is key. "If you don't," he says, "when you start the flare, excess metal will [cause it to] not seat properly."
The Smog: If your car's old enough-say, OBDI or prior, or you've got some sort of standalone engine management system, you can ditch almost all of your engine's emissions bits without affecting drivability or performance, and with nary a check engine light. That doesn't make it right and it doesn't make it legal, but it doesn't make it untrue. Most of the time, unloading all of this is about as easy as plucking the evaporative emissions canister out along with its lines, unbolting a purge solenoid or two from the firewall, and throwing it all in a pile until you get pulled over and are forced to put it all back on.
Everything Else: It's difficult having a show-worthy engine bay with all sorts of aluminum tubes and rubber hoses getting in the way. Which is exactly why tossing things like power steering pumps and your Nissan's entire heating and A/C system has got to happen. When nixing power steering, swapping steering racks for a non-power-steering version will make being able to manhandle that steering wheel without any hydraulic assistance a whole lot easier. And when ditching that heater and A/C, don't forget the less obvious bits, like that heater core behind the firewall and the wiring harness and relays that route throughout your bay.
The Ugly Side of Shaved and Tucked
Shaved and tucked engine bays aren't all rainbows and trophies. Go overboard or do it wrong and you've just made that electrical connector impossible to access or that fuel line a roadside inferno waiting to happen.
You'll Hate Chasing Down Electrical Gremlins Even More: Whoever assembled your car put that fuse box where it's at for a good reason. Turns out somebody smarter than you strategically placed just about everything underneath your hood with future accessibility in mind. In other words, those engineers wanted you to be able to swap that blown 15-amp fuse on the side of the freeway without having to disassemble your dashboard. Tuck that harness and stash away any of those fuses and relays deep enough, and you've just made diagnosing that electrical problem you're about to have a whole lot tougher.
Smog Checks? Forget About 'Em: Depending on where your car's registered, tossing or tucking away some of those engine-related bits is probably illegal. It's against the law to remove anything emissions-related no matter where you live and, in some states-we're looking at you, California-so much as relocating any of this is also a no-no, the consequences of which range from a failed emissions test to a rejected vehicle registration to a fine that you can't afford. Garcia says that you'd better know what you're up against before starting. "If you're gonna go down this road, you'd better be prepared because you won't pass a visual [smog] test."
Brake Fluid and Your Face: Those engineers that put that fuse box where you could get to it, they're the same ones who thought it'd be a good idea to keep those high-pressure brake lines away from you and your mug. There's a reason Honda didn't route your Accord's brake lines smack dab in the middle of your interior: the fluid passing through them exerts more than 1,500 psi and is hot enough to scald you. Flare that line wrong or seal that fitting improperly and you'll do more than singe the hair on your legs.
Say Buh-Bye to The Good Life: Cleaning up that engine bay of yours means getting rid of everything that'd make girls want to ride in your Civic or you mom want to borrow it. A/C compressors and power steering pumps? Get rid of 'em. Anti-lock brake systems and brake boosters? Who needs 'em? When your finished you'll be left with a sweatbox that's harder to steer and more difficult to stop but with an engine bay that looks just how you'd planned.
Tucked Engine Mounts!?
You'd tuck that whole engine of yours if you could. But you can't and, in most cases, you can't even hide those rubber-filled lumps of steel or aluminum that mount it all into your bay. Unless you've got a '92-'00 Civic or '94-'01 Integra, in which case Hasport's got something for you. You know that pair of torque mounts that bolt up underneath the frame rails and that you typically leave off in hopes of shedding a few pounds? Hasport's just released its own, which, unlike the factory ones, are strong enough to support the front half of that engine and transmission of yours and without those left- and right-side mounts up top that you've never thought of getting rid of.
Plumbing and What You're Doing Wrong
There are all sorts of things standing in between you and a well-executed engine bay. On the top of that list is you not knowing a lick about what sort of fittings, adapters, and lines you ought to be using when tucking away those brake, clutch, and fuel lines. For starters, understand that your brake system's subjected to massive pressure. The fluid that runs through it is also corrosive; use the wrong sort of hose and you won't just ruin your paint, you could ruin your face. Follow these here tips and avoid your own plumbing disaster.
- For most fluids, just about any steel-braided or nylon-covered rubber-based hose will work, but for hydraulic brake and clutch lines, be sure to use Teflon-based hose instead of rubber.
- AN fittings with their specially designed conical seals don't require any sort of sealant. Want yours to leak? Wrap it in Teflon tape or put a dab of silicone on it before tightening it down.
- Speaking of Teflon tape, leave that to Bubba the plumber and his crack. When sealant's required, like for pipe-thread fittings, for instance, use something liquid-based that's less likely to come apart and clog a fuel injector.
- Metric, BSPT, NPT, AN, JIC; there are as many types of adapters and connections as there are ways for you to bungle them up. And while you'll never be able to thread an AN adapter directly into your car's metric-based master cylinder, know that there's almost always an adapter to join together two otherwise incompatible connections.
- You think those flared brass fittings hanging next to the toilets at Home Depot are exactly what you need for that fuel line and you couldn't be more wrong. Home improvement adapters like these rely on a 45-degree flare, unlike AN fittings that are cut to 37 degrees. Combine the two for an impressive shower of fuel, coolant, or oil under your hood.
Q&A with The Pros
What's your best piece of advice for those planning on taking on their own shaved and tucked bay?
Frank Garcia, Downstar Inc.: You have to know your goal before you start. Are windshield wipers important to you? If not, take 'em out. What about power steering? Write down what you want to keep and what you want to get rid of before starting anything.
Randy Chacon, RC's Garage: Have lots of time and patience. People underestimate the work involved when they've never done it before. But once you do it you'll have a better appreciation for the people who do it day in and day out.
What sort of compromises have got to be made when shaving or tucking a bay?
FG: When you're going for a specific form or look, you're going to have to get rid of some function. There's no way around it.
RC: Some people like the [convenience] of keeping the OEM equipment, like ABS, brake boosters, A/C, and power steering. Obviously, there's a noticeable difference when you remove those things. We enthusiasts make those sacrifices to build what we dream about.
What kind of precautions would you recommend taking to make sure safety isn't compromised?
FG: If you're not comfortable assembling a brake line or a fuel line, have someone else do it. If something goes wrong, your car can catch on fire or you can die
RC: Use the right tools for the job. If you're tucking a brake system, watch a couple of YouTube videos on how to flare hard lines properly. Same with wiring; watch some videos on how to use a voltmeter and how to properly solder connections and cover the wire correctly. Most importantly, don't rush it. Always think about what you're doing and do it right.
What are some simple things someone who's not ready for a full shave and tuck can do to their engine bay?
FG: One thing you can do if you've got a Honda is flip the brake booster upside down. It'll hide the vacuum line down low where you won't see it. Also, I noticed a huge difference from just adding hardware when I started.
RC: Go back to the basics, like with a simple headlight harness tuck, battery relocation, or hardline-to-AN fuel conversion. Simple and clean will never go out of style.
The Goods You Need
Downstar Inc. Beauty Washers: You're not ready for that fully overhauled engine bay yet and that's fine. Downstar's got the polished-up, low-profile hardware you need to replace those ugly-looking OEM lumps and clean up that engine bay in a hurry. Downstar's got applications for most popular Japanese cars and universal hardware that'll work if they don't.
Downstar Inc. Tuckin' Brakes Kits: You're ready to stuff that brake system of yours underneath the dash but you've got no idea what sort of fittings and lines to use. Downstar's brake line kits let you stick that proportioning valve out of the way, and since the lines are professionally assembled and tested, eliminate the chances of your Miata getting tossed into a wall.
Wilwood Brake Master Cylinders: Whether you're looking for a smaller and lower-profile master cylinder than what your car came with or something that'll allow you to safely remove that brake booster, Wilwood's probably got an application for you and for about the same money you'd spend for another stock one.