Cloned Kurzheck

We look at a 907K re-creation that holds its own next to works racers.

Photo: Cloned Kurzheck 1
June 30, 2022

Cloned sports cars can be a tricky subject to navigate. Some enthusiasts grumble that clones—often entry-level models upgraded to higher-trim specs—are pretenders that don’t live up to an original’s pedigree or character. On the other hand, a high-quality build of a more affordable Porsche, like a 1969-1973 911T, into an expensive one, like a 1973 911 Carrera RS 2.7, is often a glorious sight to behold and experience. Perhaps clones aren’t such a bad thing, as long as they aren’t passed off as something they’re not and are built to or above the standard of a factory original.

What do you do, though, if you want a particular car that has no affordable trim models on which to build? The answer is you build a re-creation, also known as a continuation, when produced by the original carmaker years later. However, these cars are also often a topic of criticism. Like clones, if a re-creation has a fully disclosed origin and is constructed to factory specs, then it functions as an accessible version of something that otherwise wouldn’t be available to be enjoyed. That brings us to the 907K you see here.

Engineer, fabricator, and the owner of this 907, Erik Shahoian, developed the skills to create this machine over the last 30+ years. He developed a serious interest in Porsches after getting a ride in his cousin Ken’s 934 tribute at the age of 18 and a passion for fixing and building cars while studying at UC Berkeley in the ’80s. He went on to own a 914 and later an early 911 with a Sportomatic transmission that became his first Porsche rebuild project in 1989. After seeing his restored 911, some friends started asking Shahoian to do work on their cars. This led him to do a fuel injection rebuild, rust repair, and Light Ivory respray on the late Cris Huergas’ now legendary R Gruppe 1969 911S.

Shahoian took things to the next level in 1995 when he started building a factory-correct Porsche 910 replica along with partner Mark Hutchinson after studying and photographing a factory-original 910 at Sears Point Raceway in Sonoma, California. The result was a gorgeous re-creation that graced the pages of Excellence in February 2004 (#126).

Photo: Cloned Kurzheck 2

The cabin of this 907K replica is tight but correct to a factory-original version down to the millimeter.

Through his build of the 910, Shahoian made friends and contacts with a small but enthusiastic community of classic Porsche race car collectors, builders, and parts makers. For example, while he was dyno testing an engine at Jerry Woods’ shop, he met Dale Miller, who was restoring a few 908-03s. Shahoian then fabricated replacement titanium ball joints for the 908s and reverse-engineered their titanium axles. That work led to brainstorming a new build.

“Somehow, Dale and I got on the topic of my favorite Porsche prototype cars, the 907 and 908-02,” says Shahoian. “He made my year when he offered an opportunity for me to build a continuation-style 907—my dream car—with his help.” A 907K build was pursued, as Miller could help with all the bodywork for a K. Shahoian also loved how the 907K looked.

Built in 1967-1968, there was a 907K (for Kurzheck, or short tail) for medium-speed tracks and a 907L (for Langheck, or long-tail) for higher-speed courses. Other than the rear bodywork, the 907K and L models were nearly identical. Today, the 907K is best known for being driven to overall wins in the 12 Hours of Sebring and the Targa Florio in 1968.

In 2004, Shahoian met enthusiast Carl Thompson, who eventually managed and owned the entire Vasak Polak Porsche factory racing parts collection. Shahoian was amazed at Thompson’s parts warehouse and discussed the 907K project. Luckily, Thompson was in possession of extremely rare factory 907 drawings. With a clear goal in mind and blueprints to follow, Shahoian began gathering parts and collected most of the essential pieces to replicate a 907K.

Photo: Cloned Kurzheck 3

Many parts used from this build—like this oil tank—are originals that still wear their original factory part number labels.

Shahoian was able to find many of the rarer parts through friends and connections in the Porsche world.

“When I was helping Dale Miller with his 908-03 project, he and my friend ‘Big Ron’ Gruener gave me NOS spare parts for my project as generous gifts—things like the factory aluminum castings that get welded to the ends of the oil cooler core,” he recalls. “Dale said those were the last OE ones on the planet as he handed them to me. Their generosity put many correct features on the car.”

Next, Shahoian imported metric-sized steel tubing from Germany and started the years-long fabrication and build process. The frame was assembled using TIG and MIG welding as well as brazing with silicon-bronze alloy throughout. It took 750 hours (nearly 94 full workdays!) to fabricate the tube frame alone. Some parts of this build were very straightforward, while other tasks called for some drastic measures.

“Part of the 907K project involved taking the very last NOS 907/908 steering rack purchased from Carl Thompson and replicating it in every detail,” explains Shahoian. “This was two months of engineering and involved at least ten vendors including machine shops, gear hobbing specialists, casting magnesium, precision grinding, heat treating, plating, etcetera.”

Photo: Cloned Kurzheck 4

While the complex steering rack build went smoothly, the simple location of an oil fitting proved tricky.

“One day when Dale was visiting, he pointed out that I had positioned a through-the-frame oil fitting in the wrong location—just slightly, but it mattered,” says Shahoian. “I was fortunate to be in Stuttgart on vacation, and the Porsche Museum had a 908-02—which was similar to the 907—on display. With my girlfriend as the lookout for the museum authorities, I was able to lean far over the ropes and position a camera under the dash of that car without contact or instability and snap a dozen photos of the oil line fitting—exactly how it was angled out of the tube frame. I was obsessed with making sure every detail of my 907K continuation was exactly as original.”

The bodywork is the correct thickness and weight as the original and was hand laminated using NOS German twill glass cloth. The aluminum door frames and rear and front cover frames were hand-formed over wood mandrels and even Shahoian’s knees, then TIG welded and carefully fitted and formed to fit the fiberglass panels. Next, the windows were thermoformed using some of the very last sheets of original Plexi 10 amber-colored plastic. This material is virtually extinct now, and no manufacturers will reproduce it due to toxicity and cost.

Despite being a re-creation, this 907 does have a fair number of factory components. In fact, about 25 percent of the car is made up of original Porsche parts, according to Shahoian.

Photo: Cloned Kurzheck 5

“There are NOS suspension components on it, like the front uprights, hollow axles, front and rear hubs, wheel nuts, front A-arms, and rear wishbones,” he says. “There are other pieces too, like the front and rear anti-roll bars, body clamps, the oil catch tank, and the gauges and lights, which still have the factory part number tags on them.”

All four corners of this 907 have original part-numbered coil-over suspension parts with original springs. Shahoian swaps those in and out with modern Bilstein units depending on when and where the car is being raced. Even so, the original and aftermarket suspension parts look so similar that only Shahoian can tell the difference without pulling them apart.

The yellow anodized 30-mm (1.2-in.) oil hose fittings seen throughout the car are originals that once crossed the finish line at Le Mans in a 936 and were recycled years ago—removed with their tired oil hoses. These were simply cleaned and reused. The oil and fuel tanks were fabricated to factory specs using 5052-T3 aluminum and TIG welding and took months to build.

Underneath the 907K’s fiberglass engine cover rests a 2.0-liter naturally aspirated air-cooled flat-six built to Type 901/20 specs (most commonly found in the 906 and 910 racers) that puts out 210 horsepower at 8,000 rpm and 152 lb-ft of torque at 6,200 rpm.

Photo: Cloned Kurzheck 6

Shahoian meticulously re-created the factory wiring harness and controls.

“The 907s ran both six and eight-cylinder engines,” says Shahoian. “The frame was designed for both. The first 907s to compete ran six-cylinder 906 engines due to the limited availability of Type 771 flat-eight engines (mostly seen in the 906, 907, 909, and 910). We have not yet located an affordable 771, so we opted to build a correct 1,995cc racing engine.”

The flat-six in our feature 907K has custom pistons that yield a 12.5:1 compression ratio (up from the 10.3:1 ratio in the factory 901/20 engines). It also has 46 IDA Weber carburetors, 38-mm (1.5 in.) intake and exhaust ports, a modified 906 grind cam, straight-cut timing intermediate shaft gears, and custom ported twin-plug 1969 911S cylinder heads.

The transmission casing is from a 914 that has been machined and modified to fit in the 907 frame. The ratios are a CHMRV arrangement (Porsche identified each transmission cog ratio with a letter. In this case, C is 2.4; H 1.684; M 1.318; R 1.08; V 0.925) as specified in an original 907 owner’s booklet Shahoian used for reference. The final drive ratio is changed depending on where the car is racing. The shift linkage is identical to the original from the wooden knob to the engine bay, but a custom shift arm goes to the gearbox as necessitated by the 914 housing. Shahoian also swapped out the factory Nadella axles for 930-gen 911 Turbo ones. Veteran vintage Porsche racers told him the titanium Nadella axles sometimes disintegrated back in the day.

The brakes are NOS 907 single-piston calipers from Carl Thompson fitted with Pagid Orange racing pads that squeeze 267-mm (10.5-in.) AP Racing vented rotors that are identical to originals. The fragile NOS 907 cast brake pedal that they first used was replaced with a beefier 935 replica part in the interest of safety.

Photo: Cloned Kurzheck 7

As with most race cars, this machine has multiple sets of wheels. It is typically seen on Crosswaithe & Gardiner magnesium replicas or factory original Porsche racing wheels measuring 13 × 8 inches up front and 13 × 12 inches in back. Shahoian also made a custom set of three-piece mag wheels as backups. The tires are Avon racing rubber measuring 8.2/22-13 in front and 10.5/23-13 in back.

“Other than the 914 transmission housing, the axles, and the brake pedal, the car is factory correct,” says Shahoian.

However, even after all the parts for the car were there, the 907K sat incomplete on a lift in Shahoian’s shop for five years, as it wasn’t a pressing project. That’s when his friend and racer Jason Richardson entered the picture.

“I was the spark that fed the fire to where we are today,” says Richardson. “I recommended that we finish the car and compete in vintage racing. That started—I believe—in 2015.” The goal was to get the car up and running in Sportscar Vintage Racing Association (SVRA) and the Classic Sports Racing Group (CSRG) competition at Sonoma, Laguna Seca, and Thunder Hill Raceway. Richardson would drive the finished product because, as Shahoian put it, “The 907K had no practical purpose without Jason—I can’t fit in it with a helmet on.”

Photo: Cloned Kurzheck 8

Every weekend Shahoian and Richardson put in a tremendous number of hours to complete the 907K. That hard work paid off. Once the car was assembled, it needed almost no tuning or adjustments before it went racing. They only changed a front anti-roll bar setting and tire pressures. However, after a few trips to the track, they became frustrated with oil and ignition system issues.

“The oiling system was perfectly accurate to the original in every detail, yet we kept losing oil pressure in hard right turns,” says Shahoian. “We also had overflow issues from the breather tank and loss of power at high speeds.”

He traced the overflow issue to a custom oil filter fitting that had been left a mere 5.0 mm (0.2 in.) too long and the oil light problem to an oil line that was also too long. It took five minutes on a lathe with the fitting, installing a shorter oil suction line, and relocating the oil tank closer to the engine to correct the issues. Next, it was time to sort the ignition woes.

“We found that our ignition problem was an original Bosch pull switch that powered the ignition relays,” continues Shahoian. “Jason was losing ignition randomly on some turns, and the car died on a practice run. Corrosion and vibration had loosened the screw.” Tightening a loose wire connection above the footwell was all it took to make things right.

Photo: Cloned Kurzheck 9

Many of this car’s hose fittings were once attached to a 936 that raced at Le Mans.

What’s this machine like driven in anger on a race track?

“Off the green light, the 907K has good pull and torque, but it really starts to shine when the tires come to temp after about two laps,” says Richardson. “It loves fast tracks and wants to be at wide-open throttle. The other cars it competes with have a hard time keeping up through the corners. If you see it race at Sonoma, for example, and see the car go through the S curves, you will see me gap the other cars.”

To date, this 907K has had two podium finishes and a top-five in the CSRG series, and a top-five in an SVRA race.

“The other huge factor that helps me as a driver is the brakes,” continues Richardson. “I am a late braker, and the 907 has my back in this department. Porsche had a great brake set up for its time in 1967. And once I am hard on the brakes, the car is perfectly stable—there’s no pulling or sliding. So when charging for a corner, I commonly will brake just a little later to allow me to pass going into that corner.”

Photo: Cloned Kurzheck 10

Are there things Richardson would change or doesn’t like, though?

“From a driver’s standpoint, I would say the things I like least would be visibility. The way the cockpit is set up, I sit very low, and the top of the steering wheel does cross my field of vision. Also, the long throw of the shifter is challenging. A short-throw shifter would have been fantastic. Another challenge is the heat. This was, I believe, the first car Porsche added the small trap door in the nose for what we now call a ‘Cool Suit’. It’s a system that runs cold water through tubing sewn into my shirt and is an absolute must in this car. The temperatures can get overwhelming, especially on summer race days.”

In the end, Shahoian fulfilled his dream of building a 907.

“I make my living as a mechanical engineer and product developer, so I invent new ways of doing things in medical devices, novel consumer products, and electric vehicles,” he says. “The 907K project was all about faithfully replicating something that exists as a piece of history, and that is a fun change of pace. I get to be an archeologist and a technologist as well as a machinist and fabricator.”

Regardless of its few shortcomings, this machine is a testament to Shahoian’s diligence and hard work. The car is stunning down to the smallest detail in person and compares favorably with original 907s I’ve had the opportunity to look over at the Porsche Museum, Porsche Museum warehouse, and a few Rennsport Reunions. Whoever says cloning and replicating classic race cars is a bad thing has never seen a faithfully recreated machine of this caliber before.

Also from Issue 293

  • 993 RS Drive
  • Terracotta Warrior 911
  • The Ten-Buck 356 Cabriolet
  • Market Update: 996 & 997
  • Boxster Shooting Brake
  • Interview: Kévin Estre
  • Porsche Electrical Issues & Voltage Drops
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