Carrera 4 “RS”

A 1991 964 Carrera 4 is turned into a streetable track-day machine.

Carrera 4 “RS” 1
December 8, 2017

Larry Kosilla was born to his career. As a young boy, he remembers asking his mother for a bucket of soap and water and cleaning his pedal fire truck. He was one of the few little boys in the world who wanted to be clean. When Kosilla grew up, he studied economics at the University of Virginia and headed to the Mercantile Exchange, where he worked for a natural-gas commodities trader. While he couldn’t stand the job, Kosilla was getting good business experience. He was also detailing cars on the side to make ends meet.

From there he started working for a service in New York that rented cars out for film, television, and print work. His job was to make sure the vehicles looked perfect inside and out, make sure the models and actors didn’t scratch the paint, and then bring the cars back safe. Kosilla soon formulated his own products to use in his detailing business, then later created his own brand, AMMO, to sell them to others. With both businesses going full bore, Kosilla, who bracket-raced a Ford Mustang 5.0 in his teens and later owned a Chevy Impala SS, decided it was time to buy a new performance car. This time, though, it would be German.

Kosilla fell in love with the 964 the first time he saw one, and to his mind, the Carrera 4 version sits in the sweet spot for naturally aspirated air-cooled 911s. It features a 247-hp 3.6-liter flat-six engine, an all-wheel-drive system derived from the one in the 959 supercar, a classic-looking five-gauge dashboard, effective air conditioning, and coil springs instead of torsion bars underneath. But when Kosilla discovered this particular 1991 C4 for sale on Long Island, New York in April 2013, he had some concerns.

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While that time and place likely won’t set off any alarm bells for most readers, car buyers in the Northeastern United States remember it as the spring after Hurricane Sandy (a.k.a. Superstorm Sandy), which in late 2012 flooded large areas of the Mid-Atlantic states. Kosilla wanted to make sure this Porsche wasn’t one of the tens of thousands of vehicles that had been completely submerged just a few months prior.

Speaking with the 964’s owner, Kosilla learned that, as the storm got close to Long Island, the Porsche was packed with as many belongings as possible and driven to higher ground. While the C4 survived unscathed, its owner’s home was a different story; the car was being sold to raise money to rebuild. Kosilla was concerned he might be taking advantage of someone in a tough spot, but when the 964’s owner reassured him that he was okay with the sale, the deal was done.

The next step was an inspection, which Kosilla recorded and uploaded to YouTube. It was clear the Porsche had been well-maintained, but the engine definitely needed some help. There was a slow leak from two of the cylinders, which Kosilla suspected might be due to the 1989-1991 964 engines’ lack of head gaskets. While most cars were later retrofitted with the gaskets under warranty, this particular car had somehow missed the recall.

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The choices were: Pull the 3.6-liter engine and repair it, or recreate the 3.8-liter RS motor he’d been dreaming about. It wasn’t that tough a call, and it ended up making better financial sense when the flat six was stripped to bare bones. The dream was realized with all work being done at Speedsport Tuning in Danbury, Connecticut. LN Engineering supplied new Nickies pistons and cylinders, which were supplemented with EBS Racing valve springs with titanium retainers and Web Cam’s Super Sport racing camshafts.

The factory head-gasket upgrade was performed and a lightweight RS flywheel and clutch were installed, after which the built six was topped off with an FVD Brombacher exhaust for a mean, nasty sound. After some dyno pulls, which also appeared on YouTube and began attracting attention, as well as sponsorship, Kosilla had Steve Wong burn a new engine-management chip specifically for this engine to achieve a better air/fuel mixture. In the end, the 964 put out 302 horsepower, which is pretty good given that, in the mid-1990s, all-out 993 RSR race cars were making just shy of 400 hp.

Given the newfound go, Kosilla figured he needed more whoa, so the 964 was treated to a custom-fitted 993 big-brake kit. Then it was time to sample the result on the race track.

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After a few events, Kosilla decided it was time to beef up the C4’s track credentials. For the interior, he selected Sparco Evo II seats and five-point harnesses to replace the stock units, along with a DAS roll bar. Bigger brake ducts and a front spoiler from FVD were fitted to the car’s nose, while JRZ RS PRO adjustable suspension, RS America anti-roll bars (24 mm front and 18 mm rear), and Magnus Walker Design wheels were installed underneath. The final step was a race-ready alignment, and the 3,294-pound ballerina was ready to perform.

With the updates complete, Kosilla headed back to the track—and while running at New Jersey Motorsports Park, the C4 got stuck in third gear. It turned out the 3.8’s extra power had broken a shift fork in the stock G50 five-speed gearbox. Needless to say, the transmission was rebuilt with race-spec internals.

But there was still one last issue that had to be addressed. Kosilla knew when he bought the Porsche there was some rust around the lower part of the windshield (a weak spot on 964s), but when he started digging, he discovered the rot was more advanced than he had thought, extending into the cowl area. The 964 was entrusted to J&B Bodyworks in Mount Vernon, New York, where, instead of cutting the cowl at the A-pillars, a whole new roof was installed.

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Kosilla had never used the car’s sunroof, and when he found out a non-sunroof roof would be 25 pounds lighter and offer more headroom, he jumped in with both feet. The Porsche was stripped down to bare metal and meticulously prepped for four coats of Bentley’s Beluga Black and two coats of clear. The freshly painted car would later be wrapped in Xpel Ultimate paint protection film.

During reassembly, the C4’s interior received a new layer of soundproofing, a black Alcantara headliner, and new front and rear glass. The somewhat frail stock headlights were upgraded with super-bright custom-made units.

While all this was going on, Kosilla got a phone call from Dan Pye of Augment Wheel Company (AWC) in Oakville, Ontario, Canada. Pye had been following the car’s journey online and wanted to know what Kosilla’s dream set of wheels would be. The answer was easy: “I would love to have my D90s back!”

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The 964’s original 16-inch “D90” wheels had been retired to make room for the bigger brakes, but that didn’t deter Pye. AWC carefully measured a set of the factory wheels—everything from the thickness of the spokes and the size and shape of the windows to the depth of the legs and the overall convex radius—then produced a 17-inch two-piece version. Kosilla had the new wheels painted black and bolted in place.

Sitting on the false grid at Palmer Motorsports Park in Palmer, Massachusetts, Kosilla’s 964 stands out from the crowd. Not only because it’s so clean, as you’d expect, but because it still looks like a street car, complete with a stereo, rather than a stripped-out track toy. The perception of road car diminishes considerably when I turn the ignition key.

All the work Kosilla has lavished on the Porsche quickly makes itself evident. The C4’s built-in understeer has been noticeably reduced, allowing me to carry more speed through the corners. Less push also means I can get back on the throttle earlier and then seamlessly bang my way through the beefed-up gearbox. The revised suspension and wheel/tire setup confidently put the extra power to the ground with no hint of drama.

After all the hot laps are done, this pristine C4 doesn’t get locked away in a trailer. Instead, it gets ready to do battle once again out on the open roads. But Kosilla’s dream Carrera 4 “RS” will be back soon, as clean and fast as ever.

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  • 2018 718 Cayman
  • 1970s 911 Turbo History
  • 1970 914-6 GT Racer
  • Porsche Swept Daytona in ’68
  • 2018 Macan GTS
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