2006 Corvette

There's something intrinsically appealing about a Corvette that appears to be bulging at the seams. The widened rear fenders of the '90 ZR-1, for example, wrapped around the steamroller Goodyears like Cindy Crawford wearing a just-tight-enough pair of jeans in a Guess? ad. The same goes today for the '06 Z06 and its flared bodywork.

Corvette builder and racer Jeff Nowicki, of Specter Werkes/Sports, knows all about the subtleties of the Corvette form. He's been enhancing the Vette's shape at his Troy, Michigan, shop for the better part of 10 years, and he's the first one to admit too much of a good thing can ruin the sensual shape of the car.

"The Corvette's [shape] has always been carefully proportioned," he says. "There are ways of accenting it that enhance the muscular, performance ethic, but too-wide panels or outlandish wings detract from its essence."

Nowicki transferred his philosophy into fiberglass with the original, C5-based Corvette GTR. These made-to-order supercars featured wider replacement front and rear fenders, as well as correspondingly widened fascias. The GTRs had a more dramatic "Coke bottle" silhouette, which helped dramatize the cars' lines and cover wide rubber, but the uninitiated had to look twice to see the difference-unless the GTR was parked next to a "skinny" C5.

The GTR was a complete, turnkey car offered through two exclusive Chevy dealers, but Specter also developed a group of a la carte exterior, interior, and performance upgrades under the Group 5 label. These weren't-and aren't-simply the GTR components offered to the DIYer. The Group 5 components consist of unique ground effects, fascias, spoilers, and more. And rather than being sold through a couple of dealers, the Group 5 parts were offered to anyone who wished to order them directly or drop off his Vette at the Specter shop for upfitting.

Now, Specter Werkes has launched the Group 6 lineup for the sixth-generation Corvette. Yes, it's a looker, with fender flares and an appropriately sized rear spoiler, but it's also a Z06 fighter. Specter's prototype car pumps out more than 500 normally aspirated horses from the 6.0-liter LS2 V-8.

Specter Werkes/Sports chief Jeff Nowicki poses with our cover car.

Like the GTR and Group 5 designs, the Group 6 complement of exterior upgrades embellishes the factory's form without cartoonish exaggeration. But where the C5 exterior components offer a smooth, tailored look, the Group 6 has a harder, racetrack demeanor-as if the designer sport coat has given way to a bicep-stretched T-shirt.

"The basic form of the C6 is a race car, and the Group 6 components build on that," says Nowicki.

The success of Corvettes-including the LeMans-winning factory team-on the racetrack undoubtedly influenced the Group 6's design. Several of Nowicki's customers have left cars at the shop with instructions for Specter Werkes to give them the look of a road-going racecar.

Well executed in form and proportion, the bolt-on Group 6 parts include an extractor hood, an aero package with rear spoiler, and rear wheel flares. The silver prototype in our photos wears HRE 840R wheels wrapped in Michelin PS2 rubber, sized 275/35-19 in front and 335/30-20 in the rear.

"We wanted to give the car a more aggressive stance, while keeping the identity of the production design," Nowicki says. "The front chin is functional, channeling air to the brake ducts, and gives the car a meaner look. The rear wheel flares allow 12-inch-wide tires to fit."

Specter Werkes/Sports offers the individual components of the Group 6 package separately.

Photo by Jay Heath

Naturally Aspirated
With the willing, 400-horse LS2-which retains elements of the previous LS6 engine, including the cylinder heads-as a starting point, the Group 6's engine was treated to Specter Werkes' "Matrix 1" makeover, which included a special-grind camshaft, CNC-ported cylinder heads (with larger valves), a Lingenfelter cold-air box, LG Motorsports long-tube headers (with 3-inch X-pipe) blowing into a Corsa exhaust system, and a pan full of Mobil 1 oil. It's a relatively simple combination that, while requiring some careful tuning for optimal performance, delivers 525 hp and 435 lb-ft of torque.

This is race-car horsepower and time-warping torque. Besides the output, however, is the Group 6's rumble and idle quality. It barks to life with a raspy growl, thanks to the long-tubes and Corsa pipes, but it settles into a thumping, low-rpm idle that instantly reminds us of the solid-lifter days of yore. The moment you hear it, you think one thing: "Man, that thing's got some cam."

With 500-plus horsepower, the Group 6 has no trouble hazing the nubs off the new Michelin PS2s. Throttle response is more immediate, too, thanks to a few well-placed taps of the laptop keyboard.

Surprisingly, all this power is channeled through an otherwise stock drivetrain. The cooling system is stock, and so are the six-speed manual transmission and clutch.

"All the factory parts are more than adequate for the power," says Nowicki.