With its racing pedigree, the Corvette's natural home is on the racetrack. Many owners are not content to be trackside spectators, but are compelled to let their Vettes run free on the open tarmac. Eric Birkness is one of those owners, and his '06 Z06 has been designed with a racing flair.
Following more than a decade of competitive shifter-kart racing and several years of motocross and enduro experience, Birkness set his sights on a means of excitement with less risk than motorcycles and less punishment than karts. "The biggest problem with karts is that you get bruises on your sides and on your legs every race weekend, just from the cornering force," he explains. To achieve this goal he decided to move on to taking fullsize cars on the track.
Like many Vette owners, Birkness grew up with a passion for America's sports car. He recalls a particular fondness for a pair of scale-model Stingrays from his youth. When he finally was able to acquire a 1:1 scale Corvette, Birkness pounced on an '01 Z06 and fitted it with a supercharger for 550 horsepower. The C5 Z was short lived, as a batch of bad fuel led to detonation during his first lap at a track day and destroyed a pair of pistons. Rather than attempting to sort out the blown (and blown-up) C5, Birkness felt it best to move on to a car better suited to the track.
The pursuit of a proficient track car naturally led Birkness to the C6 Z06, and he purchased one of his own in December 2005. Initially, the plan was to keep modifications light to preserve street use, but that changed during a track day at Watkins Glen. While lapping the track, the car got "a little sideways in the esses" at 120 mph, and the instructor suggested that the car be equipped with a rollcage. Birkness was at first reluctant to carve up the interior of his brand-new Vette, but he ultimately decided it was in his best interest to follow this sage advice. In this act, the die was cast and the Z06 began its transformation to its current radical form.
While at another open-track event at Watkins Glen, Birkness was awestruck by the Whelen Motorsports C6 race car's comparative advantage at carrying speed through corners. Seeking such performance of his own, he inquired with Kerry Hitt of Advanced Composite Products (ACP) about outfitting his Z06 with the racer's bodywork.
The ACP ZR/T body kit goes beyond the mere cosmetic enhancement of most exterior modifications by providing enhanced performance. Originally built for use in the SCCA World Challenge professional racing series, the kit boasts performance developed from aerodynamic testing in the GM wind tunnel. ACP claims its kit will generate in excess of 700 pounds of additional downforce at speed. It features a heavily vented hood to reduce lift, a large wing to keep the rear tires planted, and rear fenders widened by 1/2-inch on each side to fit wider rubber. Birkness offers a glowing review. "The aero stuff really works," he explains. "The car turns better and stops better. It makes the car way more stable at high speed and really plants the rearend out of corners."
Ultimately, the visual impact of the body kit is equally as impressive as its functionality. The combination of aggressive lines, racing appointments, exposed carbon fiber, and the black finish lend the car an exceptionally menacing appearance. This runs somewhat contrary to Birkness's original intent, as he explains: "I wanted a black car so it would look understated and not get so much attention, but with the bodywork and big wing it gets lots of stares." The car even has a tendency to slow traffic when being transported to racetracks on an open trailer.
Sharpening the Z06's corner-carving abilities was a must, and the suspension has been significantly enhanced with T-1 springs and sway bars installed front and rear. A set of 1 1/4-inch-drop billet uprights and Moton shocks at each corner give the car a hunkered-down stance befitting its capabilities. In order to shave off speed in a hurry, a Stop Tech big-brake kit was installed and cooled by a set of custom carbon-fiber brake ducts. On the street, the Z wears a set of CCW SP500 wheels shod in Michelin Pilot Sport Cup tires; CCW C14 wheels with Hoosier R6 slicks are used at the track.