Piers’ 240Z: From First Principles

Piers Hugh Smith recently took to mechanics through cafe racers — a consequence of lockdown boredom while living in London. Underneath his apartment complex, he began spending his spare hours rebuilding a classic motorcycle with the assistance of battery-powered lights and powertools as there were no outlets in the parking lot available to him.

“It was a 1970s Honda CB550 and it was a total wreck. I found it in a commercial waste site. I took the opportunity as a way to learn about rebuilding engines. It was just so simple and light — I could pick it up easily and install just about everything on my own.”

It also set the stage for his later projects by having a motor quite similar to a modern car’s. “Through some forum trawling and badgering a few friends over the phone, I learned my way around its carbureted inline-four and got it into a reasonable state. In fact, I commuted to work in London for about a year on it — a great bike for traffic that’s much smaller than modern bikes with similar displacement.”

Piers educated himself on the essentials of internal combustion and learn his way around an air-cooled four-stroke motor fairly quickly — thanks largely to his obsessive commitment to understanding the fundamentals, and the simple nature of a classic engine.

The smooth, swooping lines of a fastback had always spoken to him and his aesthetic tastes, which, after deciding to try his hand at restoring four-wheeled vehicles, made choosing the titular vehicle easy.

“I remember seeing a 240Z with the Pandem kit years ago while I was in school — it just blended the original curves of the car with something aggressive, but sympathetic to its basic shape. Plus, the fastback has great aftermarket support, so the combination of visual and practical appeal drove me towards modifying one myself.

This one came up for sale as an unfinished project. I was still in the UK at the time, where the car was, and the bodykit had been installed. The owner, a bodywork specialist, was asking a reasonable price since, mechanically speaking, it was a complete mess. The wiring was horrid, the interior was mostly MDF from the DIY store, and the mechanics were in poor state.

I got the car ambitiously; thinking it’d be a quick and easy finish, but it took a year and a half to get it sorted,” he admitted.

Over those eighteen months, he took to this car with the same fervor he had with his cafe racers. There was a plan, however — this was no flight of fancy.

Sympathetic Modernizing at a Reasonable Cost

“The whole idea was to learn how the chassis works and modernize it while preserving the original design intent and spending pragmatically on maximizing the driving experience. I thought about engine swapping the L24 with a BMW B58, but in the interest of preserving the soul of the car, I decided to keep the original engine and keep it carbureted, albeit with some modern updates to make it more usable.

It involved a full rebuild of the engine with partnership of Four Ways Engineering. It’s a basic performance setup with triple Weber DCOE40 carburetors, a bigger aluminum radiator, electric fans, a stainless straight-through exhaust, and a stainless intake. I haven’t yet dynoed it, but people with similar setups make around 180-190 to the wheels. I also converted it to electronic ignition and labored over the wiring by introducing common grounds and independent relays to ensure reliability, then I installed a newer and slightly taller diff from a later automatic 240SX to improve cruising manners and replace the tired original unit.”

The powerplant functional, Piers moved onto the chassis and its lengthy list of to-dos. “I wanted to modernize the handling, first by stiffening the body with some bracing, and then by welding BC BR coilovers to the original spindles and rear hubs.

“You buy a standard weld-in coilover that is the right size for the car, then you weld it to the original front spindle. It’s a generic fit,” he added.

Along with the new shocks, he turned to Silver Project, a Polish company specializing in 240Z suspension components builds, for their adjustable control arms and tension rods given the cost of securing US imported parts in the UK.

In keeping with the classic looks, he decided to updated the interior with some modest street buckets and an aluminum center console from Skillard, an Oregon-based aftermarket specialist, as well as a couple new powdercoated items to maintain a vintage period look inspired by aviation panels of the era.

The car has a weak point in its chassis stiffness; there is a lot to be gained by taking some load out of the original thin steel. Piers made up for this by introducing Apex Engineered triangulated strut braces in the front and rear.

Piers made the move across the Atlantic to San Francisco this January and brought his beloved Z with him, though it lagged behind by six months. Once he’d shipped and registered the car stateside, he made the next bolt move — to track the car. Last weekend’s event at Sonoma was a first for both him and the car he’d spent so long restoring.

A Day of Firsts

“While I didn’t build it for the track, I wanted it to be fun and capable. I drive it to work, to social events, and on backroads, too. I wanted versatility, mainly. That said, it was easy to see how testing the car on track could improve the product, ultimately.

The first day, it was flooding the cylinders with fuel at high revs on the main circuit, so I did a carb sync, changed the fuel ratio and jetting, and then went back out for the third session, where the car had much better power delivery and more predictable behavior. However, with the additional speed, I blew out the brake booster. In every other sense, the car performed really well considering its age as well as my experience as a builder.

Getting to run with my friends in modern cars demonstrated how these older cars are so much more analog; needing a thoughtful approach from the driver. I spent most of my time trying to preserve my momentum because there’s not much power, and it’s only available across a narrow powerband. I can’t just floor it; nothing happens. I need to listen to the car and plan ahead to make sure the car is ready for the next segment as it does not respond well to sudden changes in demand.

Now, through driving the car aggressively, I know that there’s an iterative list of improvements to make, particularly in the suspension and braking realm. It’s got too much dive, and it still has OEM brakes. There are cheap OEM disc-brake setups that bolt in fairly easily with some adapters. I might also add a five-speed box from the 240SX, another bolt-in item, then leave this car alone. It would sound good, stop well, and produce a reasonable amount of power. I think I would be very close to hitting my build objective of a stand out resto-mod which delivers a huge smile to the driver and passenger at a reasonable level of expense.

I’ve not yet spent much time on aero. Given the speed of the car, my goals for the build, and the marginal return of aero modifications, I do not think it offers the best bang for buck at this stage, but is undeniably important and something to consider later on.

The car’s sitting on much wider tires than standard: 9.5 in the front and 10.5 in the rear, and those might be slightly too wide for the power and stiffness. There need to be other changes in the package to support a footprint that size. This was a case of form getting in the way of function rather than sticking true to my original goal: for beauty in their harmony.

I can only say that I was really happy with the event. It was my first-ever track event. Having my friends there was great — to drive alongside them and to have their emotional support when I was spending time under the hood wondering why I didn’t just bring something fuel injected!”

This car, as beautiful and as expensive-looking as it is, was built primarily to teach Piers some of the intricacies of the chassis without costing him a fortune. “With this one, the obvious thing to do is to keep spending time on the setup; I made sure everything’s adjustable as there’s a lot to be learned through making the most of the car as it is before endless upgrades. As long as they worked well enough, I picked mid-tier parts to keep costs reasonable, too.

His second Z car, which he’s just started building, will be built to further his understanding of balancing performance, aesthetics, cost, and usability. “The chassis has already been seam welded and acid dipped with full length frame rails to make the thin monocoque frame a little bit stiffer. They’re not safe cars to begin with, and rather than engineer crumple zones, I will install a six-point cage with removable door braces. I believe that installing a cage is also the best way to stiffen the chassis. The next engine is still an original block, and the intention is to keep it naturally aspirated, but bored and stroked to get more modern levels of power.

There’s a company called Apex Engineering that does a very interesting double wishbone setup for the S30 Z cars in the front and rear. This would be an easy way to achieve more predictable suspension dynamics and a stiffer sub-frame style set up.

In the second car the goal is simple: to take a blank shell from first principles and combine it with what I learned in the first and use it to create a beautiful, analog, and enjoyable high performance sports car whilst staying true to the original design intent of the 240Z.

Now when I’m driving the car, I feel more confident given I understand the basics of how it works, and I think the education the car has given me has made me a more sympathetic driver. There remains a very long way to go, but understanding why the car behaves the way it does has really come from putting it together myself.

I spend most of my day behind a desk, so this is a great distraction from my normal day and focus on creating something immediately tangible — it has this incredibly different feeling to the rest of my time that it makes it easy to become hyper-meticulous. I keep lots of notes, so when I go down a rabbit hole on one dimension of the build, I don’t lose that learning when I actually come to implementation later on.

I remember my design teacher in high school giving me advice to sleep with a notebook on my bedside table for those wee-hour solutions — I’m glad I listened. I try to be pragmatic about what I do and don’t do, which is why I picked a readily available, well-developed car, and I try and focus on tackling areas of the build where I can be additive, rather than re-creating a solution just so I can say I did it from scratch. All of this I think maximizes learning rather than just bolting bits together.”