Cottage Industry

We head to the English heartlands to see a 1972 911E-based 935 clone that perfectly epitomizes the ethos of “built, not bought.”

Photo: Cottage Industry 1
October 26, 2023

From some angles, Richard Chamberlain’s unique creation looks like a slant-nosed 935 from days gone by, while from others, it resembles an early Group C race car. Now fitted with a mid-mounted 962-inspired engine, the most surprising fact about this gorgeous creation isn’t that it started as a 1972 911E or that—with countless racing wins over more than three decades—it is arguably the ultimate privateer racing Porsche in the UK. Instead, it’s that this machine was built in a garden shed.

Chamberlain has been a fan of Porsches for as long as he can remember. In the late 1980s, he faced a slight dilemma when he was forced to choose between keeping his 911 Carrera 3.2 or his driving license. With how he liked to drive, keeping both wasn’t an option. A friend suggested he sell the road car and buy a race car instead, and this way, his need for driving fast would be rewarded with silverware instead of being punished with tickets and license points. He duly sold the road car and bought this 911, which had been converted into an “RSR 3.5” by racer Mile Youles.

His initial legal way to go faster on public roads was by entering hillclimb events. With years of karting and Formula Ford experience, Chamberlain knew how to handle the car and enjoyed much success. However, before he bought the RSR clone, Youles raced it in the UK’s popular Intermarque series. After a few years of hillclimbs, Chamberlain decided he was ready for different thrills.

In the early 1990s, Chamberlain took the 911 back to the championship the car had been built for. In a nutshell, the Intermarque series is for homemade Group 5 cars, where almost anything goes; it is a proper ‘if you can build it, you can race it’ philosophy. But while the silhouette racers might look weird and wonderful, the racing was always serious, and Chamberlain lined up against some of the great names of motorsport of the day, such as Gerry Marshall in his Aston Martin and Win Percy in a Jaguar XJ220. He never looked back and has been circuit racing ever since.

But while it’s usual for drivers to go through a series of ever more competitive cars in ever higher tier championships, Chamberlain’s entire Porsche racing career has been behind the wheel of his trusted and beloved RSR clone…although, with more than 30 years of serious development, there is hardly anything left of the original car.

Photo: Cottage Industry 2

Currently, only the curves of the roofline are recognizable as a 911. After a few years of lightening it and squeezing more power out of the Bob Watson-prepared engine, one of the first major changes was fitting a turbo. A potent competitor had entered the series with a turbocharged Porsche, and another raced a fast Jaguar E-Type with 700 hp. Both outclassed Chamberlain to such a degree that a significant upgrade was needed to remain competitive. Bolting a turbo to the exhaust didn’t seem too hard, in theory, but it wasn’t so simple in reality.

“For 18 months, all I did was blow engines up on the dyno,” Chamberlain shrugs. Eventually, despairing at not getting the engine set up right by himself and beginning to be concerned about the mounting costs every time he needed a new block and pistons, he went to the famous racing engine builder John Judd in Rugby.

“At first, I was terrified at how expensive it would be,” says Chamberlain. “But they showed us how to do it, and all of a sudden, the engine ran perfectly rather than just exploding,” Judd had been involved in Formula One for many years, so Chamberlain doesn’t think the success he went on to have in the Intermarque series meant too much to him. The series organizers certainly took note, though.

After a couple of seasons driving rings around the opposition, he got a polite letter asking if he would please not enter again, as the other teams wanted a chance at more than just seeing the Porsche’s big rear spoiler disappear off into the distance. He obliged and, in 2003, took the opportunity to enter the Porsche Open championship…which he also dominated. After a few years of growing his trophy collection, he took another step up and joined the Britcar championship.

Here, the competition was a lot tougher, and good results weren’t a given. Still, he enjoyed the challenge as a driver and preparing and setting the car up. On the other hand, the races were up to six hours long, so they necessitated a lot of extra fuel and tires, as well as more wear and tear on other components. This meant the cost-to-fun ratio was a bit skewed the wrong way. The perfect solution, Chamberlain found, was the GT Cup, which runs 30 or 50-minute races. “These are brilliant,” he enthuses. “And the car fits perfectly into it.”

Photo: Cottage Industry 3

But at this time, in 2017, the car was still recognizable as a 911 RSR. The extreme, 935-style modifications actually began by accident; a large, fiery one.

At a GT Cup race at Silverstone, a tire blew at full tilt on Hanger Straight, and the carcass flailing around at 155 mph ripped an oil line off a turbo. Although the subsequent fireball from the oil spraying over red-hot engine components was apparently quite impressive, it destroyed everything from B-posts back.

“It happened a week before the Formula One Grand Prix,” recalls Chamberlain, “so on the TV, I could see the scorched grass where I’d come to a stop in a puddle of molten aluminum.” Thanks to the quick action of the marshals, the front end of the car escaped mostly unharmed.

Wanting to salvage what he could, Chamberlain got a plasma cutter out and basically split the car in half. But instead of just building back what he’d had before, he decided it was an excellent opportunity to engineer some serious upgrades. The first was to make the car mid-engined, something he’d been mulling over for some time but had balked at because of the amount of work involved. A year later, ably assisted by his son Matt and long-time friend and stalwart of CTR Engineering in Cambridgeshire, England, Tony Frost, the evolution version was ready.

“It went like a bomb, and we found three-quarters of a second a lap!” says Chamberlain of the re-done racer. That might not mean too much to us non-racers, but qualifying in a field of fairly well-matched GT machinery meant a significant positional boost up the grid. But it wasn’t quite as simple as that.

Photo: Cottage Industry 4

“Because the engine is in the middle, we found it was ridiculously hard to keep it cool, and for a time, it seemed there was nothing we could do,” continues Chamberlain. “With a flat floor, there was just no way to get the air out, and the car overheated so much that the cylinder heads went soft! It was obvious very quickly that we needed a water-cooled engine. A sensible person would buy a 997 engine from a scrap yard…”

Instead, a big fan of classic Porsches and their lack of complicated electronics, Chamberlain thought about finding an original 962 racing engine with water-cooled heads. One was found in the U.S….for $250,000. As such, that idea was ditched quickly. Next, he contacted XTec, a company in Stafford, England, that knows a lot about 962 powerplants.

“And so we built our own engine for somewhat less than the quarter-million dollars,” smiles Chamberlain. “But it was a massive amount of work!”

Some of the more notable components include a 930-generation 911 Turbo crankcase with a Turbo crankshaft and 935 through bolts. Inside are bespoke rods and pistons, Nickies cylinders with twin oil squirters per cylinder, genuine 935 IMSA-spec cams, and solid Porsche 935 rockers. The bespoke heads are cast from RR350 aluminum alloy. It also sports an Auto Verdi 935 “Indy” oil pump and a flat fan. The 640-hp capable engine is mounted to a six-speed Hewland LWS-200 gearbox.

Additionally, a lot of hours went into the design and creation of the water rails, a part that doesn’t exist in parts catalogs. “We did it all by trial and error, and, as we can’t weld that well, we took the idea to a couple of specialists,” says Chamberlain. “And it was even hard for them.” Another issue with the new engine was working out a practical solution between optimal aerodynamics over the front and the installation of water radiators.

Photo: Cottage Industry 5

“Where do you put them on an air-cooled Porsche 911?” Chamberlain shrugs. His son Matt has a mechanical engineering degree, and it was he who Richard credits with laboring over CAD software until they came up with a workable solution. “The whole car is an exercise in thermal management,” says the elder Chamberlain.

The highly sophisticated bodywork was all designed in-house and is another element of the project that took a long time to get right. It includes front and rear diffusers, a flat floor, a front splitter, and a twin-element rear wing. The front clamshell is a carbon fiber copy of the 1979 Le Mans-winning Kremer K3 935, reworked and modified for the specific needs of this car. The doors, roof, running boards, rear wings, and internal ducts are full carbon fiber.

The electronic systems are controlled by a Motec M150 ECU with a Motec dash and a bespoke race wiring loom. Concept Engineering made the radiators, and the Chamberlains had to work out how to duct the air in and out. As you can see, there’s not much space at all.

Chamberlain used to race with magnesium hubs from a Kremer K3, but being over 30 years old, those parts were potentially dangerous. Now, the car has in-house-designed hubs made from 7075 T651 aluminum-zinc alloy. The double wishbone suspension operates via rockers and push rods that utilize the gearbox as a fully stressed member. Damping is provided by Ohlins four-way adjustable TTX shocks that were custom made. All of this, of course, begs the question, what is left of the 1972 911E?

“Erm…not much,” says Chamberlain. “The front section of the floor, which is raised by 3.0 inches for the central diffuser, and the near side inner fenders are the same. The back floor section isn’t, though, because I smashed it into smithereens. The bottom of the B-pillar is the only other remaining part from 1972.” But as the car has always been (and probably always will be) a work in progress, Chamberlain knows there are still some areas to improve.

Photo: Cottage Industry 6

“The brakes are the Achilles heel at the moment. We have great big discs with an anti-lock brake system, but we still don’t have the braking capacity of the newer cars we race against. We have 18-inch wheels, but the latest cars have 19s and run bigger brake discs. Donnington and Oulton Park are hard on brakes, and halfway through a race, they’ve almost gone, but at Donnington, you’re braking from 170 mph twice a lap. The next project is bigger front hubs to cope with the bigger wheels.”

In the GT Cup series, Chamberlain races against the newest GT cars, such as the latest GT3 Ferraris, McLarens, Bentleys, and other non-homologated cars, like MT900 Moslers and a Lotus with a massive engine.

“It’s such a great feeling to race something you know every bolt of rather than something you just went out and bought,” says Chamberlain. “We have just Tony, another guy, and my son, and I’ll never get bored of beating teams who turn up with a 40-foot truck and 20 people.

“The only downside of running a car like this is if, or I mean when, I have an accident, repairs take a long time, as we have to make all the parts again,” he continues. “You can’t just go and buy them off the shelf. But that is far outweighed by how great is it to race a car that no one else has!”

Today, this fiery orange 935 is currently embarrassing modern machinery in the British-based GT Cup.

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