New Car Reviews

Specter Werkes Corvette GTR vs SLP Camaro ZL575 – Bow Tie Bullets

General Motors’ small-block V-8s are the Rolling Stones of engines. Over the last six decades, nearly 100 million of them have been built to power cars and trucks sold by eight American GM brands plus a slew of race cars, hot rods, boats, and a few homebuilt aircraft. To keep a thumb on the small-block’s pulse, we gave a pair of them a run through our rigorous test regimen.

When suburban-Detroit-based Jeff Nowicki needed more vitality for his Specter Werkes/Sports Corvettes, he dipped into the bottomless well of small-block parts and expertise. On the outside, the Corvette GTR looks like an action toy from the Transformers 2 movie. Under its swollen and slotted hood beats a heart that sounds like a transplant from a Sprint Cup racer. Stand clear while two Michelin radials are disciplined for misbehavior.

The Nowicki name has been part of the Corvette family for two generations. Jeff’s father, Ron Nowicki, was the chief engineer in the Corvette design studio during the C4 and C5 eras. Jeff has worked as a clay modeler and raced Camaros, and he established his own tuning business twenty years ago. Add to that fifteen or so years of campaigning Corvettes in various road-racing series. Today, ten Specter Werkes employees convert standard production models into radical customs with vastly improved performance. Last year, eight GTRs rolled out of this Troy, Michigan, shop with a fresh lease on life.

The Specter Werkes GTR is the rich man’s Z06. A base Corvette coupe is reskinned with eleven hand-laid fiberglass panels and seven molded-carbon-fiber components, and it is then sprayed with the same mercury-silver paint that Mercedes-Benz applies to the SL65 AMG. Chassis modifications include a one-inch-lower ride height, Forgeline three-piece wheels, Michelin PS2 run-flat tires, Hotchkis antiroll bars, and StopTech brakes. The GM 6.2-liter LS3 V-8 is fortified with a forged crankshaft and pistons, billet connecting rods, a wilder cam, higher-flow fuel injectors, and an LS7 clutch and flywheel. A three-eighths-inch-longer stroke bumps displacement to 6.8 liters. According to the chassis-dyno report card, 510 hp and 480 lb-ft of torque are delivered to the GTR’s 335/30YR-20 rear tires.

Inside, the door panels, seats, steering wheel, and console are trimmed in Spinneybeck leather embossed with an exotic reptile grain. The entire GTR treatment costs some $69,000, or about ten percent less than a new Z06. But before you split your piggy bank, don’t forget to add the cost of a core Corvette coupe or convertible.

The GTR we tested is owned by Mike and Michelle Cowan, a Longmont, Colorado, couple who enjoy hearing small-block thunder rattle through long-tube headers and stainless-steel exhaust pipes relieved of their catalytic converters. Even though it’s substantially heavier and packs less piston displacement than a factory-built Z06, the GTR matches the Z06’s 4.1-second 0-to-60-mph acceleration sprint on the way to an impressive 12.5-second, 121-mph quarter-mile pass. The lowered ride height provides razor-sharp turn-in, and the wide Michelins deliver well over 1 g of cornering grip with a comforting touch of understeer at the limit. The upgraded brake system does a superb job of shedding unwanted momentum on Chrysler’s challenging 1.7-mile road course.

While the factory team dithers on C7 development, Nowicki doesn’t mind filling the void with his GTR, effectively a C6.5 Corvette armed with take-no-prisoners design and performance.

SLP (Street Legal Performance) founder Ed Hamburger also knows how to squeeze extra oomph out of a small-block V-8. More than thirty years ago, he made his name as the guru of oil pans. His Toms River, New Jersey, plant converted more than 50,000 fourth-generation Pontiac Firebirds and Chevrolet Camaros into street racers for GM. Now that the Camaro is back from the dead, SLP has a sprawling family of models sporting ZL identification to resume the beat. Blame the ZL575 recently loaned to us for the permanent scorch marks adorning several southeastern Michigan neighborhoods.

This Camaro conversion is essentially the fifth-generation Z28 that GM hasn’t quite gotten around to releasing. An Eaton supercharger similar to the one fitted to the Corvette ZR1 pumps air at 6 psi into the 6.2-liter LS3, inflating output to 575 hp and 550 lb-ft. Stock engine covers are trimmed and relabeled for this duty, and the blower is fed cold air through a new low-restriction filter assembly. New mufflers and behind-the-axle pipes trumpet motor melody via four-inch exhaust tips. Stiffer springs drop the ride height an inch, and the new tubular antiroll bars are adjustable. Brembo fifteen-inch front rotors and six-piston calipers enhance stopping power.

The exterior guise includes cool twenty-inch redline wheels, a fiberglass hood equipped with a functional scoop, a raised deck-lid spoiler, a prominent SS grille badge, and various stick-on graphics for the hood, front fenders, side gills, and taillamp panel. Inside, the floor mats and headrests receive SS ZL575 logos. A numbered dash plaque, two key fobs, and a car cover are also included. SLP’s only major lapse was not replacing the Camaro’s steering wheel.

The basic ZL575 package costs $22,995 and can be purchased through any Chevy dealer. (Starting with the L99 V-8 used with the six-speed automatic yields 550 hp and ZL550 badges.) With all the options, the total surcharge rises to $32,320. Hamburger intends to limit the production run to 500 units, split equally between manual and automatic cars.

The SLP conversion boosts performance from the Camaro realm into the Corvette’s orbit. Minimizing the cloud of tire smoke during a launch can hurtle the car to 60 mph in 4.5 seconds and through the quarter mile in 12.9 seconds at 118 mph. Top speed is stuck at 158 mph because of the factory governor (which SLP will lift to 190 if you opt for even pricier Brembo calipers), but 30-to-70-mph passing times are 1.5 seconds quicker than in the stock Camaro SS. We recorded no significant gain in cornering or braking capability, in part because the ZL package adds more than 100 pounds to the car’s curb weight.

The best part is the baritone growl that bores deep into your soul. There’s a lovely burble on overrun and minimal drone during cruising. Ride motions are more vibrant than stock but quite tolerable. The ZL575’s steering delivers quick, confident moves with virtually no body roll. Dropping a few gears, cocking the wheel, and nailing the throttle lights the rear tires quicker than you can say Zippo.

Now that most of GM’s energy is devoted to staying alive, we’re lucky to have Nowicki, Hamburger, and other competent tuners to fan the eternal small-block flame.

The Specs:
Specter Werkes Corvette GTR
Engine: 6.8L V-8, 510 hp, 480 lb-ft*
Drive: Rear-wheel
*per chassis dyno

The Specs:
Engine: 6.2L supercharged V-8, 575 hp, 550 lb-ft
Drive: Rear-wheel

Automobile Test Results

  • Corvette GTR
  • Camaro ZL575
  • 0–60 MPH
  • 4.1 sec
  • 4.5 sec
  • 0–100 mph
  • 9.2
  • 9.7
  • 0–150 mph
  • 20.4
  • 22.8
  • 0–180 mph
  • 35.4
  • —
  • 1/4–MILE
  • 12.5 sec @
  • 12.9 sec @
  • 121 mph
  • 118 mph
  • 30–70 mph passing
  • 4.7 sec
  • 4.8 sec
  • 70–0 MPH Braking
  • 151 ft
  • 158 ft
  • Speed In gears
  • 1) 55 mph
  • 1) 50 mph
  • 2) 82
  • 2) 73
  • 3) 112
  • 3) 105
  • 4) 146
  • 4) 151
  • 5) 197
  • 5) 158
  • 6) 175
  • 6) 158
  • Cornering L/R
  • 1.06/1.07 g
  • 0.95/0.91 g
  • Weight
  • 3422 lb
  • 3971 lb

Buying Guide
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2019 Chevrolet Corvette

MSRP $59,495 Stingray 1LT Convertible