Reeves Callaway got his tuning start in the 1970s, adapting turbochargers to BMW’s then-new 3 Series. It was an inauspicious start that led to a comparatively successful run of turbocharged Alpha Romeo GTV6 models (about 35 were sold) in the early 1980s. Other projects kept the fledging Callaway Cars, headquartered in Old Lyme, Connecticut, busy until the alliance that would make the company a household name in the performance world.
In 1986, the first Callaway Twin Turbo Corvette was built and offered to the automotive media for evaluation. A landmark story in the November 1986 issue of Car and Driver resonated with performance-starved enthusiasts, not to mention Chevrolet. It spawned a five-year run that saw more than 500 examples produced of the unique, Chevrolet-blessed special model.
Callaway Twin Turbo Corvettes could be ordered as regular production option (RPO) B2K, with the cars shipped directly from the Bowling Green, Kentucky assembly plant to Callaway’s shop for conversion. Upon completion, they were sent to the dealer for standard new-car delivery. The conversion was even warranted under GM’s 12-month/12,000-mile warranty, with Callaway reimbursing the dealer for any time and materials related to the turbo system.
The basic engine package consisted of a pair of state-of-the-art turbochargers and air-to-air charge coolers, along with internal engine modifications necessary to withstand the forced induction. This included forged rotating parts, a specific-grind steel roller camshaft, approximately 7.5:1 pistons, and more. Some engines received block reinforcements too, including machining for splayed, four-bolt main caps. Callaway also placed its own E-PROM “chip” in the engine control computer, as was typical of the early days of tuning.
During the five-year run of the Callaway Twin Turbo, performance, engine specifications, and even the turbo systems evolved. Horsepower ranged from 345 in 1987 to more than 400 in 1991. Many owners sent their cars back to Old Lyme for additional tuning and greater power.
Early in the production span, the Callaway Twin Turbo was essentially identical to the standard production model, but a pair of NACA-style air inlets could be added to feed cool, outside air to the charge coolers. By late 1987, the cars could also be upgraded with 16- or 17-inch, five-spoke Dymag wheels that have since become iconic identifiers of Callaway Corvettes. In 1989, an Aerobody package option was added, which offered distinctive visual identification. The body package was based on the styling of the Callaway Sledgehammer Corvette that was driven from the company’s Connecticut shop to the Transportation Research Center in Ohio, blasted to 254 mph, and driven back to Connecticut. Such an achievement today would be astounding–Callaway did it 20 years ago. The Aerobody became a popular option for new customers, and many have retrofitted the unique fascias and complementing components to their earlier cars.
The mystique of the Callaway Twin Turbo was eclipsed by Chevrolet’s own exotic Corvette, the 1990-introduced ZR-1. And frankly, given the investment the ZR-1 represented, Chevy was more interested in pushing it than continuing with the Callaway Twin Turbo. Also, the 1992 introduction of the LT1 small-block and the significant changes its reverse-flow cooling system brought would have required substantial investment for adaptation of the turbo system.
Production of the unique turbo-powered cars lasted through 1991, but Callaway has retained a special relationship with Chevrolet. Our brief time with the Polo Green 1990 example seen in this story’s photos proved Callaway was a pioneer in the tuning world. It starts, idles, and drives like new. The performance won’t give a new Z06 the shakes, but the visceral thrill of a twin-turbocharged small-block is as exciting today as it was 20 years ago.
Special thanks to Cauley Chevrolet in West Bloomfield, MI for allowing us to photograph the 1990 Polo Green example in our story.
Number Built – 1987-91: 510 (448 via B2K option, 52 independent orders)
Construction – Body-on-frame
Engine – 350 cubic-inch turbocharged and intercooled, fuel-injected V-8
Power/Torque – 1987: 345 horsepower, 465 lb-ft torque, 1988/1989: 382 horsepower, 562 lb-ft torque, 1990: 390 horsepower, 562 lb-ft torque, 1991: 403 horsepower, 582 lb-ft torque
Transmissions – Four-speed manual with overdrive (early years); six-speed manual (later years), four-speed automatic
Suspension front – Independent, unequal-length control arms, fiberglass-reinforced leaf spring
Suspension rear – Independent, two lateral links and two trailing links per side, fiberglass-reinforced leaf spring
Brakes – Four-wheel disc
Length/width/height – 176/71/46 inches
Wheelbase – 96 inches
Weight – 3,300 lbs. (approx.)
0-60/quarter mile – 4.7 seconds, 13.2 seconds at 108 mph (Car and Driver, November 1986)
Top speed – 175 mph (manufacturer claim)
MPG – 17 - 24 mpg
Excellent engineering and engine build quality
Twin-turbocharged small-block makes great torque
Aura of exoticness that’s quite unlike anything else
Comparatively affordable and poised for value growth
Less-than-solid feel of the C4 chassis and body
Seat bolsters prone to wear, even on lower-mileage examples
C4s were never easy to enter or exit
Stellar power in their day, but less than a base Corvette today
Remanufactured alternator $164.79*
Brake discs and pads $53.79 (front rotor), $54.79 (rear rotor); $22.79 (pads, kit)*
Exhaust system $539.99**
Seat upholstery kit $480-$800**
*Based on information from Rockauto.com
** Based on information from Mid America Motorworks
WHAT TO PAY
1990 Callaway Twin Turbo Corvette Coupe
MSRP – $59,374
Low – $21,400
Average – $28,900
High – $33,800
*Based on prices from NADA Guides,www.nadaguides.com
Insurance cost is $535/year for a $28,900 1990 Callaway Twin Turbo Corvette Coupe. This is based on 3,000 miles per year of pleasure driving.
*Based on a quote from Heacock Classic Car Insurance,www.heacockclassic.com
WHEN TO BUY
Generally speaking, C4 models have not caught on with the collector market–yet. This means cars like the Callaway Twin Turbo can be had for relative bargains. Market prices for these cars have probably bottomed out, so any time now is a good time to invest in that Callaway you lusted after in the late-1980s.