Such a serious aerodynamics package required more chassis tuning than a common application. As Birkness explains, "It took a while to get things set up right since there was so much downforce, the front of the car would scrape with gentle braking if you were going over 150 mph." After the suspension was adapted to the Z06, it began to work in concert with the aerodynamics to provide a thrilling driving experience.
Generating 505 horsepower from the factory, the LS7 engine in the C6 Z06 is nothing to sneeze at in stock trim. However, Birkness decided to squeeze more power out of the small-block with the help of Hutter Racing Engines. In an attempt to avoid repeating the experience of his '01 Z, the plan began with building up the already formidable stock aluminum block to handle the added strain. The original hypereutectic pistons were replaced with custom 4.130-bore JE units connected to a lightened 4-inch Bryant crankshaft with Crower billet rods. Internal enhancements also include sleeved lifter bores and a priority oiling system.
To ensure adequate breathing for the athletic Vette, a Lingenfelter air intake and MAF were added; they feed factory LS7 heads that were treated to both CNC porting and a valve grind. The valves themselves were upgraded with larger Xceldyne titanium and Manley Severe Duty units on the intake and exhaust sides, respectively. The stock camshaft, meanwhile, was yanked in favor of a Comp Cams 251/256 stick with a 112-degree LSA and a towering 0.660-inch lift. Valvetrain upgrades also include Manley springs, Jesel lifters, and Manton 3/8-inch pushrods.
The factory manifolds were replaced with a set of LG Motorsports long-tube headers for rapid exhaust expulsion. The original Z06 after-cat exhaust was retained, but an LG exhaust bypass switch was installed to allow Birkness to manually open and close the muffler butterfly valves to control the volume. This setup affords the Z06 with a proper race-car rumble at idle.
A supporting cast of modifications further speaks to this car's special nature. The oiling system has been updated with a four-stage dry-sump setup from Dailey Engineering, including a billet pump and pan. The engine also features an ATI balancer and a Ron Davis radiator with a custom shroud.
With dyno tuning by Hutter Performance Center maximizing the combination, the engine produces peak output of 734 horsepower at 7,200 rpm and 608 lb-ft torque at 5,400 rpm. This translates into top speeds of 165-170 mph on the main straights at Pocono Raceway, Watkins Glen, and Virginia International Raceway. As Birkness explains, "Down the straights you can pass almost anything short of a Le Mans prototype car."
Combining increased power production with track duty necessitated a sufficiently beefed-up drivetrain. The stock TR6060 six-speed has been replaced with a Rockland Tranzilla close-ratio transmission that allows the car to go approximately 70 mph in First gear, 100 mph in Second, and 130 mph in Third. Further upgrades include an RPS twin-disc carbon clutch, a DTE Stage 5 Super Duty differential, and transmission- and differential-oil coolers to ensure efficient operation. All told, these enhancements help meet Birkness's goal of reliable on-track performance.
As with the rest of the Z06, the interior has been optimized for track performance. Hard cornering capabilities call for fixed Sparco Evo seats with Schroth Racing five-point harnesses to keep the occupants in place. A rollcage built by Phoenix Performance was added for protection; it necessitated door-panel surgery by Xtreme Auto Interiors just to fit inside the cockpit. The stock gauge cluster is augmented by a SPA Design 3 stage shift light in a custom shroud, and custom removable speaker cabinets were built for the rear hatch by Kerry Hitt of ACP. The GPS navi-gation system is still functional, and a Race Cam in-car video system captures all of the excitement at the track. In keeping with the car's race-oriented nature, an in-car fire-suppression system was also installed. While the factory heater was retained, the dry-sump upgrade required removing the air conditioning. Birkness uses a helmet cooler with fan and ice chest to keep cool and prevent his glasses from fogging up.