Peek under the hood of Gary Greenwood's '02 Z06 and you'll find an extremely potent engine. A 427ci engine replaces the LS6 with roots in the illustrious 7.0L C5-R racing block.
We flew to Houston, Texas, to see Gary's Z06. Electron Blue with the Mod Red interior, it looks pretty much stock from a distance. Closing in, you notice the Kinesis three-piece wheels and Wilwood race brakes. But you wouldn't suspect it's tubbed until you notice the P345/30-19 rear tires.
No doubt, this Z06 is horsepower-intense. However, Gary is an enthusiast who didn't intend to get into an R&D program. Plain and simple, the car was an outgrowth of getting Corvette fever.
"I grew up in the era of the late-'60s musclecars. My dad was a GM dealer. I grew up around those 454 Corvettes, SS 396 Chevelles, SS Camaros, and all the old musclecars. Really, that's what I ended up making this car," he says.
Gary's not alone. We've noticed many current C5 drivers were musclecar owners and enthusiasts in the glory days. Gary's in the chemical business from 8 to 5, and lets his passion run wild building and driving hot Corvettes in his spare time. He bought a new Z06 in 2002. He says, "I had trouble finding the color combination at the time. It seemed the dealers were scared of Electron Blue with the Mod Red interior. But I finally found one in Florida and trailered it back home.
"I started off doing cosmetic things, then I decided I wanted to do engine things. I did mainly bolt-ons at first, like an after-cat exhaust, then decided I was going to do a head/cam package. I got to thinking a stroker package sounded better. And that sounded so good that dropping in a C5-R block 427 sounded even better."
Gary worked with a talented builder named Sean Freese, who put the car together and tuned it in-house using LS1 Edit with the stock PCM. He thought so much of Sean's tuning and mechanical skills that he partnered with him in a side business called FASTECH, an LS1/LS6-based company that deals with Corvettes, GTOs, Cadillac CTS-Vs, and the Firebird/Camaro guys who want to do some serious work to their cars. "Sean has some experience with Vipers, so we're going to try to move into Vipers as well," Gary says.
With 544.5 rwhp through the cats, Gary's Z06, by everything he can gather, lays claim to being one of the highest-horsepower, street-legal, naturally aspirated, 427-powered Corvettes in the country. He believes MTI and Cartek are probably two of only a few tuners with horsepower in this ballpark. He says, "There are people pushing 560 or maybe a little more at the wheels, but I think that's without catalytic converters. We think once we get our next line of changes made, we'll be pushing 570 or so at the wheels with cats if we have any luck at all, which will put this car in a class all by itself."
Fastech is on a mission: to build the ultimate street-legal, naturally aspirated 427 in the world. Look for dyno runs of those tests in future issues.
Fastech/Auto Authority '02 Z06Current Performance Level* 544.5 rwhp with catalytic converters installed* Approximately 640 flywheel horsepower figuring 15 percent drivetrain loss* Strictly a naturally aspirated car with no power adders
Base Car* Electron Blue exterior* Modified Red interior* All factory options
Exterior* Rear tub kit with shock travel limiters* A&A Corvette Specialties rocker rails* A&A Corvette Specialties frame savers* Cleartastic bra* Shorty antenna* Lowered front and rear* Red Corvette lettering front and rear* Zaino, Zaino, Zaino
Engine* GM C5R 7.0L race block (installed at 1,249 miles)* Lunati rotating assembly* All internal friction surfaces coated* All heat exchange surfaces coated* Cam, custom grind* Valves, Ferrea one-piece steel, 2.100-inch intake/1.670-inch exhaust* Isky 295D Gold Series Tool Room springs* Ferrea titanium retainers* T&D 1.7:1 shaft-mounted roller rockers* New LS6 head castings, custom hand-finished porting* ATI Super Damper* FAST 90mm intake manifold* TPIS 90mm throttle body* Holley 36-pound injectors* VaraRam* Breathless Performance air bridge* Meziere electric water pump* Katech belt tensioner* Katech tall valve covers with coil relocation kit
Interior* Modified red parts by Vette Essentials (steering wheel, door pulls, console lid, shifter knob and boot, brake handle and boot)* Custom partitions by Twisted Interiors (modified red front panel with raised panel, Plexiglas inserts and C5 logo, black rear panel with raised panel and red neon Twisted Interiors logo, and custom formed wheelwell covers)* Vinyl lettering on steering wheel, dash, and door sills
Headers & Exhaust* Bassani 171/48-inch tri-Y headers* Bassani high-flow catalytic converters* Bassani 3-inch exhaust from catalytic converters back
Clutch* Fidanza aluminum flywheel* Ram 910 disc* Ram 402 pressure plate* McLeod billet adjustable clutch master cylinder* B&M Ripper shifter
Wheels & Tires* Kinesis K18R, Front: 18x9.5-inch* Kinesis K19R, Rear: 19x12-inch* Michelin Pilot Sport, Front: 275/40ZR18* Michelin Pilot Sport, Rear: 345/30ZR19
Brakes* Wilwood Superlite six-piston, front* Wilwood Superlite four-piston, rear* 13.8-inch replaceable, slotted rotors front and rear with red anodized hats* Goodridge stainless steel, Teflon coated lines* Speed bleeders* Motul brake fluid
The Bassani ConnectionHave you heard of tri-Y headers? They've been around for 40-50 years. "Tri-Y" means the primary tubes, four per side, dump into two tubes then into the collector. That's "four into two into one."
In contrast, typical C5 performance headers are traditional long-tube style, even on a setup like a naturally aspirated C5-R. The four primary tubes dump into one collector. That's "four into one."
Apparently, there's a power advantage with the tri-Y style. However, this advantage hasn't been fully exploited on the 427, which Gary Greenwood has gotten into with help from Bassani.
"At first, we tried Bassani's 131/44-inch tri-Ys with 211/42-inch exhausts, which was way too restrictive for the 427ci engine," Gary says. "It really cut us down on power. Then they built a prototype set of 171/48-inch tri-Ys with 3-inch-diameter exhausts. The tri-Ys go into a 211/42-inch collector, then into cats, and on the back side of the cats is a 3-inch pipe. From there, the exhaust is 3-inch all the way back." Gary would rather see the 171/48-inch tri-Y pipe merge with a 3-inch collector and 3-inch diameter pipes on either side of the catalytic converters.
He adds, "I think we'll pick up a significant amount of torque. We're working with Bassani on it now. We're gonna make this thing breathe!"