Considered by many to be the pinnacle of C5 achievement, the '04 Z06 was much more than a simple carryover from prior model years. Suspension, rather than drivetrain enhancements, were the order of the day, with the targeted goals of refining vehicle dynamics to produce the best-riding and -handling Z of its generation. A combination of higher-durometer bushings in the upper control arms, revised shock valving, and a new rear-sway-bar mount made the car a beast on the road course, while simultaneously providing a less aggressive ride at low speed. Having undergone significant development testing at the famed Nrburgring, the '04 Z06 was the perfect performance car in which to drive to work during the week and play hard on the weekends.
After owning a black '02 convertible for a couple of years, Houston's Stephanie Cemo decided that her longing for increased power and handling outweighed the top-down benefits of a convertible, and she set her sights on upgrading to a Z06. Although the final year of C5 Z06 production was winding down, a nationwide search turned up a Machine Silver Metallic six-speed Z in Atlanta. After taking delivery of the car, it wasn't long before Cemo was afflicted with the racing bug.
"My brother Jason asked me if I wanted to go to the drag strip. It sounded like fun, so off we went," she says. "Although I freaked out when he hopped out of the passenger seat as we approached the burnout box, the starting-line personnel were eager to assist me and got me lined up in the groove. After clocking a 12.5 on the first pass, it started an eight-month love affair with the drag strip, [during which] I would attend four nights a week and eventually post an 11.7 quarter-mile e.t. with just a cam swap and sticky drag radials."
With competition clearly in her blood, the lure of the road course eventually beckoned. Rather than simply attending a track day, Stephanie decided to enroll in the Skip Barber Racing School at Mazda Laguna Seca Raceway in Monterey, California. Three days of intense instruction-both in the classroom and behind the wheel of a Formula open-wheel race car-followed, during which time Cemo immersed herself in heel-and-toe downshifting, threshold braking, trail braking, corner apexing, and other performance-driving skills.
"The instruction was tremendous, and I would highly recommend it to aspiring racers and daily drivers alike," says Cemo. "In addition to learning the myriad of techniques used in competitive racing, you also work on the subtleties, such as car control, for smoother transitions that will allow you to achieve faster lap times."
In May of 2005, Cemo took on her first track day at nearby Texas World Speedway in College Station. By the third session, she had advanced from the beginner group to the intermediate category. By the end of the second day, Cemo had graduated to the advanced group. Since then, she has consistently sought instruction to refine her road-race skills and attended every available track day at TWS. Although the learning curve was steep, Cemo is now the course's newest instructor
"I love instructing students," she says. "After all, the perks of being an instructor are free track time!" Asked to explain the allure of road racing, Cemo provided the following overview of a partial lap at TWS: "Turns 1 through 3 are a series of long, left-hand sweepers with lots of track to utilize, allowing for a great deal of speed. As I accelerate down the front straight at 140 in Fourth gear, the Z06 is positioned in a straight line for the tower. I execute some trail braking for a few seconds, then get off the brakes while allowing the car to ride out to the right-hand edge of the track.
"As you see the marker to turn in to your left, you get on the gas lightly while changing your vantage point to the apex you're about to hit. Once you feel the car is 'seated in' and planted, you start to apply more and more throttle until you are flat out. As you go around Turn 2, it feels like the wheels are going to break off the car. It is amazing!"
Given the amount of racing she does-both at the drag strip and on the road course-it's not surprising that Cemo has upgraded her Z06 with a carefully selected assortment of high-performance and competition-spec parts. Starting with the suspension, the Z was lowered 2 inches via cut bushings and suspension bolts. Stock springs and Bilstein heavy-duty shocks reside on all four corners, while GM Performance Parts T1 sway bars enhance the C5 to almost Zen-like oneness with the track.
While suspension prowess is great for cutting lap times, the extra power needed to pull the Z06 out of corners or bury the tach on the back stretch provides a more visceral and immediate thrill. The stock LS6 block and heads in Cemo's Z are untouched, with the exception of a more aggressive camshaft and race-proven valvetrain components. Motorsport Technologies in Houston installed one of its custom-ground G1 cams, which boasts 228/232-degree duration, 0.588/0.575-inch lift, and a 113-degree lobe-separation angle. Manley double springs and titanium retainers work in concert with Motorsport Tech chrome-moly pushrods and factory 1.7 rockers to manage valvetrain events
A Donaldson/Blackwing air filter and smooth bellows feed air into the engine, where it is directed to a stock MAF, 78mm throttle body, and intake. Although potent in naturally aspirated form, with almost 418 rear-wheel horsepower, the diminutive 346 morphs into a real beast when squeezed with a 150-shot of nitrous. A Nitrous Express GM EFI Dual Nozzle kit, installed by Mike Pabon of Icon AutoSports in Houston, was plumbed in between the smooth bellows and throttle body and linked to a Nitrous Outlet digital window switch. Amazingly, a stock C5 fuel pump and injectors meet all of the fueling demands of the gassed engine.
A set of Kooks 1 7/8-inch stainless headers are mated to a Kooks 3-inch mid-pipe equipped with high-flow metal-matrix converters and cutouts. For non-race activities, the exhaust is routed to a Corsa Pace Car 2 1/2-inch after-cat exhaust with Pro-series tips. An SLP 160-degree thermostat and a Ron Davis Racing aluminum radiator with integral oil cooler manage engine heat during racing events. Motorsport Tech's Jayson Cohen is credited with tuning the stock PCM to ensure that the motor remains healthy both on and off the bottle. Other than some MSD 8.5mm plug wires and NGK TR-6 plugs, the ignition system remains stock.
While road racing is generally easier on driveline hardware than drag-strip flogging, the extensive nature of this Z06's performance usage necessitated upgrades all around. Shifting duties are handled by a T56 six-speed transmission reassembled by Houston-based T56 Rebuilds after a 6,200 rpm shift on slicks annihilated the mainshaft. A Hurst short-throw shifter and MGW Gripper knob provide harmonious rowing action, while a Textralia OZ-700 single-disc clutch and flywheel transmit power to the pavement. Other than a Dynotech hardened output shaft, the rear differential remains stock, right down to the GM 3.42 gears.
Whether cruising the streets of Houston or towing a race trailer to the next road-course event, Stephanie Cemo has her sights firmly set on the next level of competition, be it in the SCCA's T1 class or as a full-time driver in a professional series. Given her ferocious dedication and ability to out-handle, out-brake, and just plain out-drive her counterparts, we wouldn't bet against her.