Every generation of Corvette has been equally comfortable on the street and on the racetrack. From the early C1 racers to the contemporary Corvette Racing Team juggernaut, Chevy's performance flagship has a storied motorsports history spanning more than a half-century. Visit any open-track event today, and you're likely to find both late-model and vintage Vettes tearing up the tarmac.
Don Ondrejcak of Clearwater, Florida, is no stranger to high-speed motoring. A lifelong hot-rod and motorcycle devotee, he has owned multiple musclecars and even a 500hp Porsche 930 Turbo. But despite his longtime involvement in the hobby, Ondrejcak reached a point several years ago at which he seriously considered exiting the performance scene for good. "I had been very busy with my business and decided to sell everything but my daily drivers," he says.
Shortly after selling his last numbers-matching '69 Camaro Z28, Ondrejcak spotted an unadulterated, low-mileage '03 Corvette Z06 on a dealer lot. As he tells it, "I had never been a big fan of the C5 Corvette, but after I testdrove it, I fell in love with it!" Wanting to introduce his 17-year-old son Don Jr. to the hot-rod hobby, he purchased the car the next day. After getting hooked on the C5, the father-son team set out to build an open-track monster.
When building the car's LS6 engine, Ondrejcak shunned forced induction in favor of old-school, naturally aspirated muscle. Accordingly, all modifications were undertaken with a pragmatic approach that eschewed flash in favor of reliable results. Every upgrade was thoroughly researched using the Corvette Forum and other Web sites. Although he was new to LS engines, Ondrejcak overcame the idiosyncrasies of the LS6 and found it to be similar to previous small-block Chevys, albeit with better build quality.
On top of the internally stock block reside a pair of Texas Speed & Performance Stage 2.5 ported cylinder heads fitted with stainless steel valves, PRC Gold dual valvesprings, Viton oil seals, and titanium retainers. The Texas Speed Magic Stick V.3 camshaft features 237/242 degrees of duration, 0.603/0.609-inch lift ratings, and a 114-degree lobe-separation angle. The rest of the valvetrain comprises GM Performance Parts Cadillac CTS-V roller lifters, TSP hardened pushrods, and an LS2 timing chain with a GMPP damper.
Meeting the rapacious air needs are a Vengeance-ported FAST 90mm intake combined with a TPIS 90mm throttle body with coolant bypass. The induction system includes a Raptor XXL air filter, smooth intake couplers, and a Z06 Shop high-flow air bridge. Ondrejcak also designed and fabricated an air opening in the front license-plate frame using stainless steel mesh.
The Z's gluttonous fuel demands are met with Comtec Performance fuel rails, FAST 36-lb/hr fuel injectors, and a Racetronix fuel-pump-harness upgrade. The ignition system is enhanced by NGK TR55IX iridium spark plugs, Granatelli wires, and DEI plug-boot booties. PCM tuning was left to Tampa tuner Jeremy Formato.
As it blasts through the gears around the track, the Z performs an aria ranging from guttural lows to a piercing high-rev contralto. The exhaust system begins with stainless steel Dynatech 1 3/4-inch long-tube headers mounted with heavy-duty ARP header studs. These expel gases through either high-flow cats or off-road bypass pipes and into a 2 1/4-inch cross-pipe before exiting through a Borla Stinger after-cat system.
Ondrejcak's hands-on approach goes far beyond the level of involvement of the average shade-tree mechanic. Working on a lift in his garage, he and his son performed all of the car's customization work, excluding the paint and tune. He even tried his hand at fabricating and designed a custom catch-can system for the engine. The sum of Ondrejcak's mechanical meddling is an impressive 510 hp and 400 lb-ft torque at the wheels.
This prodigious power is transferred rearward with the aid of an RPS Stage 3 clutch and an RPS Synergy flywheel. The transaxle is bolstered by DTE transmission and differential braces, while an Elite Engineering trans-tunnel plate helps reduce cockpit temperatures and stiffens the car. Race-ready shifting is facilitated by the obligatory CAGS delete and a B&M Ripper shifter topped with a Delrin C5-R knob.
Track-day heroics come courtesy of an enhanced suspension system with road-race alignment. The setup includes beefy front and rear GMPP T1 sway bars with adjustable Heim joints and Pfadt coilovers. Originally the car was lowered and fitted with Bilstein shocks, but Ondrejcak found that as the monoleaf springs flattened out, the rearend became exceedingly stiff and unyielding. The transition to coilovers has made the car much easier to operate on the highway, while sacrificing nothing in performance. Falken Azenis RT-615 tires are wrapped around powdercoated black 18x10.5-inch C5 Z06 wheels for street driving. A separate set of stock Z06 wheels shod in Hoosier slicks is employed at the track.
In attempt to rein in the Z's newfound power, the factory brakes have been upgraded with Brembo slotted-and-drilled rotors and Performance Friction Z brake pads. While Ondrejcak believes there's still more power to be extracted from the Z, he feels the car's mildly upgraded binders are already near their limit at close to 150 mph on Sebring International Raceway's Ullman Straight. Before moving to the next level, he plans to install the Brembo big-brake kit currently reposing in his garage.
All exterior modifications have been carried out with function in mind and undertaken primarily to augment performance. The MCM carbon-fiber hood and hood seal reduce front-end lift at high speeds. A shorty antenna minimizes drag, and a set of RK Sport canards generate downforce in the front. All paint work was handled by Corvette Classics in Tarpon Springs. The ominous black faade is broken only by a violent red gash on either side of the hood bulge. The overall effect of the exterior is not to plead for your attention, but to dare you to turn your back on it.
Beneath the hood, even the engine compartment stands out for the fastidious attention to detail evident there. Abear Motorsports billet-aluminum valve covers-anodized black with chrome lettering-are exquisite to behold, and, unlike some aftermarket covers, do not require relocating the coil packs. Underhood carbon-fiber trim from Carbling adds a race-inspired touch to the presentation.
Inside the cockpit, the original black interior has been given new life with Torch Red upholstery inserts. On track days, the driver's throne is swapped with a Corbeau AFX racing seat. The interior is adorned with the requisite racing appointments, including a Hardbar harness bar and camera mount, RJS five-point harnesses, a fire extinguisher, and a Raptor shift light. The car also features an owner-installed Escort XR3 laser detection system to limit contributions to the constabulary.
The Z06 sees most of its track time at Chin Motorsports high-performance driving events at Sebring. While Ondrejcak doesn't obsess over lap times, the effectiveness of his Vette is evident in his victory in this year's YearOne Experience autocross competition at Road Atlanta. He has used the Z06 to teach his son about racing as well as mechanics. Although he only rides along now, Don Jr. will soon be attending a racing school in preparation to progress to autocrossing his own Camaro.
There's no question this '03 Z06 pays tribute to the Corvette's lineage with its blistering track performance. But perhaps more important, the project that spawned it has allowed Don Ondrejcak to share his automotive passion with his son, just as his own father did with him. "It is a labor of love for both of us," he says. Bursting with expertly executed modifications and a trunkload of open-track cred, this is one Corvette that lives up to the marque's legendary performance heritage.