The 1984-96 C4 Corvette brought GM's flagship sports car into a new era of technology and refinement. Features such as the new "uniframe" construction, transverse leaf spring front suspension, sleek glass hatchback, and LCD gauge cluster made this Corvette feel modern, but the standard 230-horsepower L98 V8 left many enthusiasts wishing for more performance. GM would eventually respond in 1990 with the Corvette ZR-1, but back in the mid-80s, a company called Callaway Cars was quietly working on a twin-turbocharged C4 variant that would get the whole world's attention. The Callaway Twin Turbo Corvette was available through Chevrolet dealers under RPO B2K and offered European supercar performance at a fraction of the cost, plus a full factory warranty.
Photos courtesy of Mecum Auctions, Bring a Trailer, and Callaway Cars
The History of Callaway Cars
Callaway Cars was founded in 1977 by Reeves Callaway, the son of Callaway Golf founder Ely Callaway Jr. Reeves had a passion for auto racing, but couldn't afford a full-time racing career, so he became a driving instructor at Bondurant Racing School (another name enthusiasts should recognize). While working there, he began experimenting with turbocharger systems to increase the performance of the school's cars, and eventually started offering aftermarket turbo kits for BMW, VW, Porsche, Audi, Mercedes, and Alfa Romeo vehicles.
Above: This 1989 Callaway Twin Turbo Vette was sold in 2024 on Bring a Trailer for just $42,500. With only 32k miles on the odometer, this seems like a steal of a price!
One of Reeves' turbocharged Alfa Romeos caught the attention of Dave McLellan, GM's Chief Engineer for the Corvette. This led to Callaway Cars developing a turn-key, twin-turbocharged version of the C4 Corvette that received GM's official blessing.
About the Callaway Twin Turbo Corvette
Starting in 1987, the Callaway Twin Turbo package could be ordered from select Chevrolet dealers under Regular Production Option (RPO) code B2K. The B2K package cost $19,995 on top of the cost of a standard Corvette, resulting in an out-the-door price of approximately $50,000. Best of all, it was supported by GM's standard warranty, exactly like a regular Corvette.
The heart of the Callaway Twin Turbo was an L98 engine rebuilt with stronger internals — low-compression forged pistons, forged crankshaft, stainless valves and valve springs, improved oiling system, and four-bolt caps for the main bearings. A secondary fuel injection system was added to support the turbos without interfering with the factory emissions system, and a larger radiator was added to keep the engine cool.
A pair of T04 turbos, twin intercoolers, and specialized ducting on the hood and undercarriage provided forced induction to the engine. The result was 345 horsepower, 465 ft-lbs of torque, 0-60 in the mid-4-second range, and a top speed of 178mph. This put the Callaway Twin Turbo firmly in the performance realm of Ferrari, Lamborghini, and Porsche, but for roughly half the price.
The Callaway Twin Turbo had much more than just a potent engine. In addition to any ordinary options the Corvette buyer selected — such as power-adjustable leather sport seats, Delco-Bose sound system, and electronic climate control — it also received Dymag magnesium wheels, special badges, and could be optioned with Callaway's AeroBody package (as seen in these photos). The AeroBody option was designed to reduce drag and improve high-speed stability. It also made it obvious to onlookers that this is no normal C4 Corvette.
Later in the Callaway Twin Turbo production run, power output was increased several times. In 1988, it rose to 382 horsepower and 562 ft-lbs of torque. In 1990, power increased again to 390hp, while torque stayed the same. For the final 1991 model year, it reached 402 horsepower and 582 ft-lbs.
Above: This teal 1991 Callaway Twin Turbo Corvette was one of 62 built during the final year of production.
Approximately 10 of the 1991 Callaway Corvettes were turned into what the company called Speedsters. These Callaway Speedsters featured an open cockpit and an ultra-low windshield profile reminiscent of chop-top hot rods of the past.
The gloss black 1991 Callaway Twin Turbo Speedster pictured here was reportedly owned by famous director James Cameron. (Photo via Wikimedia Commons, CC BY-SA 3.0)
The Ultimate Twin Turbo Vette: Callaway Sledgehammer
In 1988, one Callaway Twin Turbo Corvette was handpicked by Reeves Callaway to become something even more special: the one-of-a-kind Callaway Sledgehammer. As the name implies, it was designed to pulverize the competition, and it did exactly that.
The Callaway Sledgehammer dialed performance to the maximum with two T04B turbochargers, custom front-mount intercoolers, a ported intake manifold, eight ultra-high-flow fuel injectors, and a whopping 22psi of boost. The underlying engine was built by John Lingenfelter with forged crank, pistons, rods, custom heads, inconel valves, and an aggressive cam.
The result was an earth-shattering 880 horsepower and 772 ft-lbs of torque. At the Ohio Transportation Research Center oval track, Callaway pushed it to a world-record-setting 254 mile per hour top speed — a record it would hold for the next 11 years. Callaway actually drove the car to and from the track, proving it was a truly streetable supercar, not just a fragile trailer queen.
The Callaway Sledgehammer showed the whole world what a C4 Corvette could do with world-class tuning and no holds barred. Hagerty's senior auction editor Andrew Newton wrote, “It’s a one-off, and its top speed rivals seven-figure supercars even 30+ years after it was built.”
For a look back at how the Callaway Twin Turbo Corvette was received back in its heyday, check out this 1990 video review from MotorWeek, which compares the Callaway to GM's own Corvette ZR-1.
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