Air suspension in a Datsun 240Z is nothing like a bolt-on modification like what you see with modern trucks. The Z has a unibody construction, which makes everything trickier. The engine bay is cramped, and there's barely any room to work with in there. Anyone who wants to get this modification right needs solid fabrication skills and plenty of patience to plan everything out.
The whole point of this upgrade is to keep what makes the Z so legendary, as you add the adjustability that comes with modern air suspension systems. It's a tough balance to strike, but when it's done right, the results are worth it.
The stock strut towers were never designed for the lateral forces that air bags create during their compression cycles. Early builders who didn't reinforce these areas ended up with cracked towers after just one season of hard driving. Factory weld spacing actually changes quite a bit between different model years, and those differences affect how the loads distribute through the entire chassis.
The rear suspension conversion gets much trickier because the original leaf spring perches won't work with air bags at all. Some builders go all out and build custom 4-link setups that have adjustable arms. Other builders choose trailing arm designs since they're easier to install, though you do lose some adjustability if you go that path. You need to get creative with the whole setup since the management systems and compressors have to squeeze into the Z's tight spaces, and you've still got to keep your trunk usable somehow. Tank placement also becomes a challenge in these compact spaces.
The structure of your Z has some characteristics that you need to know about before picking up any cutting or welding tools. Let's check out the different mounting options that will get your 240Z riding just right!
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Your 240Z and Its Body Structure
The 240Z uses a unibody construction, and it's actually quite a bit different from what you'd find in traditional body-on-frame vehicles. There aren't any separate frame rails underneath to carry the load. Each panel and structural member in the car has to share the weight and stress together. This particular design makes the car lighter and quicker to respond on the road. But it also means you need to think about how forces travel through all that metal.
When you swap coilovers for air bags, it changes the way that force moves through your car's structure. A coilover works as a rigid post and pushes straight up into the strut tower with all its force concentrated in one small area. An air bag is very different, though. As it inflates, it expands outward and creates pressure points across a much wider area. This distinction is important, and it matters every time you drive.
The SCCA races in the 1970s taught Z car drivers this exact lesson, and they learned it through some pretty expensive failures. Drivers would push their cars hard through corners weekend after weekend, and then they'd find that cracks were starting to appear around the strut towers after just a few racing events. All that repeated pounding and stress showed the weak areas that everyday street driving would never expose. Eventually, these racers figured out where they needed to add reinforcement plates and braces to stop their cars from literally tearing themselves apart on the track.
The difference is like pressing down on a table with your fist compared to pressing it with your open palm. Your fist concentrates every bit of force into one small area. But your palm spreads that same force out over a bigger area. Air bags work more like your palm does. But even with that wider distribution, they still need the right support structure to distribute all that force safely through the unibody.
Reinforcement plates and tower braces are the parts that can save you money in the long run. Skipping them is asking for real problems. Your car could be dead for weeks as you hunt for replacement parts or try to find a welder who can fix everything!
Custom Work Your Front Struts Need
The front suspension on a 240Z needs a lot of extra work if you want to mount air struts properly. Those strut towers were never meant to take the forces that air suspension puts on them. Just about every builder I've seen reinforces the towers first with welded steel plates or some type of bolt-on brace system.
Air Lift Performance struts won't drop right into your stock mounting points. The upper mounts are going to need custom adapter plates, or you'll have to fabricate something from scratch. You're going to have to measure everything multiple times until you get it just right. The mounting angle actually matters more than anything else in the whole installation.
Mount them at the wrong angle, and those air bags will fail within a few months. They have to compress and extend in a straight vertical line. Even minor side loading creates weak areas in the rubber that eventually wear through. Plenty of Z owners have already paid for this mistake the hard way.
Camber plates are going to give you a lot more adjustment options beyond ride height. After you get everything mounted up right, you'll be able to dial in your alignment settings the way you need them to be. The combination of adjustable camber and variable ride height has the control that static suspension just can't give you.
After everything is installed, you should cycle the suspension through its entire travel range. You should test for clearance at full compression and again at full extension. The bags need plenty of room to expand without hitting the fender wells or frame rails. Brake lines and wiring harnesses sometimes get in the way, too, and those might need to be moved or trimmed back.
The entire front setup needs patience if you want to get it done correctly, since each modification that you make is going to affect something else in the suspension system. You also need to take your time with the test fits and the measurements. Once those mounts are welded in place, that geometry is permanent!
Your Rear Suspension Options
The rear suspension on a 240Z works differently than what you'll find up front. Those original leaf spring mounting points weren't built with air bags in mind, and they're positioned in the wrong places for what we need. The geometry is way off from what an air suspension needs, and the stress points don't line up with where you'd actually want them for this type of conversion.
Custom brackets are mandatory for the rear installation. There's no way around this requirement, and every builder I've worked with discovers this pretty fast. Most of them go with a 4-link setup, and the reason makes plenty of sense. A 4-link has the exact mounting points that you need for your air bags, and it fixes some of the suspension geometry problems that have plagued these cars for years. Two big problems get solved with one modification, and that's why it's become the standard.
The differential housing is where the installation gets a bit complicated. Air bags need space to work properly and must compress and extend freely without interference from anything else back there. Frame rail notching is pretty common, and you might need to reroute some brake lines, too. The spare tire well is another area that usually needs attention. Some builders remove it, and others just modify it enough to make room for the new parts.
Most professional shops now actually include adjustable control arms whenever they do an air suspension install. Once the air suspension is all set up, these control arms are what allow you to dial in just how you want the car to behave. You can adjust the pinion angle, and it matters quite a bit for performance. And you get much better control over how the car behaves when you step on the gas and accelerate hard. The trailing arm versus multi-link debate never goes away in the 240Z community. Trailing arms are the easier option to work with, and they're also much easier to maintain over time. Multi-link setups give you better handling, but they demand serious fabrication skills and extremely precise measurements during installation.
The 4-link configuration lands somewhere between these two extremes and explains why it's become the go-to option for most builds. Your final choice depends on two main factors. Budget plays a big part, obviously. But how you actually plan to drive the car matters just as much.
Tank and Compressor Setup for Your Z
Space is always at a premium in the 240Z, and air management parts take up more room. A 5-gallon tank may be standard in newer cars. But it's just not going to happen in the Z. Most builders go with 2 - or 3-gallon tanks, and even those can be a challenge to fit right. The area behind the seats is cramped, and the rear hatch doesn't have much extra space either.
Compressor placement turns out to be one choice that really matters. Bolt that compressor directly to the sheet metal, and the vibrations will travel through every body panel in the car. The noise gets old fast on highway drives where the steady droning gets unbearable. A simple rubber isolation mount between the compressor and the metal makes all the difference in the world.
Temperature management is something else that deserves attention when you're planning the install. Compressors generate plenty of heat during normal operation, and they need decent airflow to work properly. Box one in too tightly, and the trapped heat will kill it prematurely.
AccuAir's ENDO-VT system has gained a strong following with Z owners for a reason. Everything integrates into one compact package instead of having separate tanks and valves eating up space throughout the trunk. The installation stays clean and also leaves room for whatever else needs to go back there.
Water accumulation is a part of running an air system, and the moisture trap needs regular draining to stay healthy. Mount that trap somewhere accessible, or you'll never actually drain it. I've seen plenty of systems with hidden moisture traps that have corroded valves after a year because nobody could reach them for routine maintenance!
Power and Wiring Changes You Need
Most builders who take on electrical work on their 240Z usually run separate circuits instead of trying to work with what's already there. The factory wiring harness in these cars is pretty simple because these cars were built in the early seventies. Back then, the wires weren't designed to handle the amount of power that air management systems need today. The best strategy is to run fresh dedicated power lines directly from the battery to your new parts.
The alternator that came with your car probably won't cut it anymore either. Air compressors are power-hungry beasts that can pull 30 to 50 amps every time they fire up. Add that extra load on top of everything else that your car already needs to run, and the math stops working pretty fast. A higher output alternator is mandatory at this point. The alternative is a dead battery at the worst possible moment - not a situation anyone wants to deal with.
Where you put your switches depends on what type of look you're after. Most builders will cut into the center console and mount the controls right where the radio or heater controls normally live. Some builders want to keep that factory appearance intact, so they'll tuck the switches under the dash or hide them inside the glove box. Either way works just fine. The only requirement is being able to reach the controls without fumbling around when you need to adjust your ride height on the fly.
Ground connections deserve extra attention on cars that are this old. After half a century of wear and tear, those original ground points are almost certainly corroded or loose at this point. An air suspension system with a bad ground will exhibit all sorts of weird behaviors that'll drive you crazy. What you want is clean bare metal touching bare metal for a solid connection.
Relay placement needs some thought about heat and moisture exposure. The engine bay runs way too hot for electronics, and water tends to pool in the footwells during rainy weather. Behind the dash or somewhere in the rear hatch area usually works best for most builds. The fuses that you choose should protect your wiring without tripping every 5 minutes for no reason.
Front Coilovers with Rear Air Bags
Hybrid suspension setups have become very popular with Z builders. The idea is pretty simple - you run traditional coilovers up front and then install air bags in the rear only.
This configuration makes everything easier in ways that matter day to day. You can still adjust your stance for shows or adapt to different driving conditions whenever you want. At the same time, you maintain the predictable performance that makes weekend canyon runs so fun. Your front end delivers steady and responsive performance right when it counts.
Your driving gets a whole lot easier when air lines and valve failures aren't always on your mind. Your morning commute should be about making it to work - not worrying if the suspension will hold up!
Weight distribution benefits are another big bonus with this setup. Coilovers up front mean that your compressor isn't always cycling during aggressive driving sessions. The system runs much more efficiently since it only needs to maintain the pressure in the rear bags. Your compressor also works less every time you hit the twisties.
The big downside with this setup is that you lose front adjustability completely. You can't lower the nose for shows or raise it when you need to get over very steep driveways. For most builders, though, the simpler, more reliable setup makes this worth the compromise. The rear height adjustment alone gives you enough control over your stance anyway and works just fine unless you're after an extreme show build.
Build Your Dream Car
Air suspension on a Z is one modification that can go either way. Do it right and you'll love every minute of driving it. The best strategy is to know your particular car inside and out and have a solid plan for where you want to take the build. These cars have been modified in every way imaginable for more than 50 years now. Each successful build turns into part of this massive pool of knowledge that everyone in the community can learn from. The builds that run great for years and the ones that become money pits have one main difference. The successful ones always take the extra time to strengthen the weak areas and mount each component in the perfect location for that particular chassis.
One of the best advantages of these car modifications now is that you have decades of other builders' trial and error to learn from. Somewhere out there, a racer back in the 1970s had already found which areas on the chassis needed reinforcement for heavy modifications. And somewhere else, a builder last month posted their clever fix for mounting an air tank in the spare tire well. Your job is to collect all that accumulated knowledge and work out which pieces apply to your particular build and your own goals. Some owners want a reliable everyday driver that works for their commute without any drama. Others are after a show car with the absolute perfect stance, and they'll gladly put up with the extra complexity to get there.
The reason all this effort pays off is that you get a car that performs just the way you imagined it would. A classic Z that can drop low for cruising downtown and then rise back up for carving through the best canyon roads is something pretty special to drive. Of course, you'll spend lots of hours measuring and cutting and welding, and you'll probably have to redo a few parts when they don't work out the first time - it's just a part of the process with these cars.
Since we're already talking about Z builds and what makes them special, let me mention something about parts quality that matters quite a bit. At Skillard, we've been around for years, and we've earned a reputation with Datsun owners because our custom parts actually fit the way they should. We also manufacture these really nice lightweight aluminum door cards that cut down on weight where it counts, and center consoles that are designed specifically for air management controls. If you want to change up the exterior as you work on stance, our bumpers, spoilers and body pieces all work together to give you the exact look you're after. Check us out at Skillard.com and you'll find the exact parts your build needs.
