1991 Callaway - Witnessing The SuperNatural

More than 20 years on, Callaway's ultrarare CR-1 continues to defy belief

Christopher R. Phillip May 29, 2012 0 Comment(s)
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In 1992, Callaway Cars--already soaring high on the success of the RPO B2K '87-'91 Twin Turbo Corvettes--introduced the SuperNaturals, a lineup of highly tuned, naturally aspirated C4 Vettes that elevated factory performance to not-of-this-world proportions. In addition to the LT1- and LT4-based '92-'96 SuperNaturals, Callaway built a total of 17 ZR-1–based SuperNatural CR-1s from 1992 to 1995, making these some of the rarest Corvettes on earth today.

"The birth of the SuperNatural program came about when General Motors announced that the Corvette's L98 engine would [be] replaced by the LT1," Callaway Cars' Mike Vendetto says. "GM chose not to invest in the tooling expense for the new turbocharger hardware and engine-management calibration for the Gen II engine."

Before the public ever saw an LT1 in a production Corvette, Callaway engineers were hard at work developing a high-performance halo car to succeed the twin-turbo L98 version.

"Turbocharging was costly when done properly, which made for a prohibitive retail price," Vendetto continues. "It also made exhaust-emissions compliance difficult, requiring federal certification of the entire turbocharged vehicle. Consequently, after Callaway Cars' Twin Turbo Corvette contract with Chevrolet had lapsed, it introduced a series of naturally aspirated, emissions compliant LT5- and LT1-based engines, ranging from 404 to 490 bhp. They were ‘super naturally' aspirated, so that's how the name SuperNatural came about."

Vemp 1208 1991 Callaway Witnessing The Supernatural 001 2/8

Two years earlier--on Memorial Day Weekend, 1990, to be exact--Callaway Cars brought a research-and-development SuperNatural CR-1 to the Long Island Corvette Owners Association's show-and-go at Lime Rock Raceway in Lakeville, Connecticut, to gauge Corvette enthusiasts' reactions.

Tony Cardiello, from Brooklyn, New York, recalls attending the event. "I was a Callaway Cars fanatic from the moment I read about its twin-turbo C4, so I was already very familiar with the company," he says "I was blown away by the SuperNatural, and made up my mind right then and there that I'd own one some day."

In April 1991, Cardiello took delivery of a Bright Red '91 ZR-1 from Malcolm Chevrolet in Paramus, New Jersey. Its sticker price of $69,000 (more than double that of a base Corvette) would have shocked most people, but it was a justifiable price of admission for a man determined to own a SuperNatural.

"I visited Callaway Cars on numerous occasions and discussed purchasing the SuperNatural CR-1 conversion for my ZR-1," Cardiello says. "I met the company's engine engineers, fabricators, and installers; test-drove a SuperNatural CR-1; picked out the options I wanted--which was all of them--and left a deposit. In April 1992, Reeves Callaway called me and said, ‘We're ready for your ZR-1. Bring it on over.'"

It took approximately two 10-hour shifts for the Bowling Green Corvette Assembly Plant to assemble Cardiello's ZR-1, but its conversion to SuperNatural status took nearly four months. (Contrasted with today, Callaway converts Corvettes in approximately two weeks.) The cost of the conversion was $55,000, but with it came exclusivity--only two fully optioned SuperNatural CR-1s were built in the program's history.

"Several factors contributed to the time required to produce the SuperNaturals," Vendetto explains. "Cardiello's car received the AeroBody option, which entailed removing much of the OEM bodywork and replacing it with new Callaway body panels and brackets, and so on. Because we always want a better- than-OEM fit, a lot of time was spent on the assembly process. The car was also completely painted.

"From a mechanical perspective, the LT5 cylinder heads were meticulously reworked--the castings were carefully ported and machined to re-contour inlet and exhaust paths without compromising the reliability of the parts. It took extra time to avoid damaging the LT5 cylinder head castings' relatively thin port walls. Removing and disassembling the engine, and reassembling it with the Callaway-specific components--as one would build a race engine--then installing it for an OEM appearance was also time consuming.

"The build timing was also affected by the fact that only a handful of CR-1s were produced. Callaway wanted to make sure the final product met its stringent, better-than-OE quality standards before the car was delivered, and the CR-1 content was still being defined as the early cars [like Cardiello's] were being built.

"Probably even more relevant, Callaway Cars' OEM-oriented product-development process takes longer, compared with automotive aftermarket manufacturers and tuners. When the SuperNaturals were built, we had just finished our OE contract with Chevrolet, which came immediately after our OE contract with Alfa Romeo had ended."

Cardiello took delivery of Callaway SuperNatural No. 8 in July of that year. The next month, he showcased it at Corvettes at Carlisle. "Nobody knew what it was, and it drew a lot of attention," he says. "Even Corvette Chief Engineer Dave McClellan came over and asked for a ride in it--and, of course, I obliged."

Twenty years later, Cardiello hasn't changed the manner in which he enjoys his SuperNatural one bit. He attends Corvette shows in the Tri-State area and occasionally attends Corvette get-togethers that require a road-trip, like the two times he's driven the car to the National Corvette Museum. He only competes for People's Choice awards and has earned four of them to date. He's never taken the CR-1 to a dragstrip, has no intention of ever doing so, and hasn't performed a single modification. "Its value is to be the way it was delivered," he says.

"To this day, Corvette fans still come up to me and ask what a SuperNatural is," Cardiello concludes. "It's a testament to the SuperNatural's timeless styling. Two decades after it was brand new, it still looks like a supercar that's coming out next year. I could have bought four brand-new Corvettes or any exotic of my choice for my investment in my Supernatural. I made the right choice."

'91 CALLAWAY SUPERNATURAL 490 CR-1
OWNER Tony Cardiello; Brooklyn, New York
BLOCK Cast aluminum
DISPLACEMENT 350 ci
COMPRESSION RATIO 11.25:1
HEADS LT5 cast-aluminum (fully ported with reconfigured combustion chambers, modified valve seats, Callaway valvesprings, and titanium retainers)
VALVES 1.54/1.38
CAMSHAFTS Four Callaway overhead roller (252/252-deg [primary], 272/252-deg [secondary] timing, 0.390/0.390-in lift)
CAM FOLLOWERS Callaway
PISTONS Callaway-spec forged aluminum (custom manufactured by JE)
CRANKSHAFT Callaway-spec forged steel RODS Callaway-spec forged steel (custom manufactured by Carrillo)
INTAKE MANIFOLD Ported LT5 aluminum
THROTTLE BODY Ported factory twin 59mm
FUEL INJECTORS Callaway (increased volume)
FUEL PUMP Dual LT5
IGNITION Stock
EXHAUST SYSTEM Callaway stainless-steel headers and cats, 3-in pipes, and balance tube
TRANSMISSION ZF six-speed manual
CLUTCH Centerforce Dual Friction
DRIVESHAFT Heavy duty
FRONT SUSPENSION Callaway doubleadjustable coilovers and HD sway bar
REAR SUSPENSION Callaway doubleadjustable coilovers and HD sway bar
REAREND HD Dana 44 with 4.09 gears
FRONT BRAKES Brembo Indy Billet six-piston (manufactured to Callaway specs)
REAR BRAKES Brembo Indy Billet four-piston (manufactured to Callaway specs)
WHEELS Dymag magnesium; 17x9.5 (front), 17x11 (rear)
FRONT TIRES Bridgestone RE71 275/40ZR17
REAR TIRES Bridgestone RE71 315/35ZR17
FUEL OCTANE 93
WEIGHT 3,500
QUARTER-MILE 12.15 sec at 120 mph (mfr rating) 0-60 4.1 sec (mfr rating)
CURRENT MILEAGE 37,000
MILES DRIVEN YEARLY Approximately 750

Callaway Supernatural CR-1 Options

  • Callaway Aerobody
  • Spies Hecker paint
  • LT5 Engine Performance Package:
    • -Blueprinted assembly
      -Forged crank, rods, and pistons
      -Special Callaway-grind cams
      -Special Callaway head assemblies
      -Ported intake and high-flow induction
      -Special engine-management computer chip
  • Centerforce clutch with lightweight single-mass flywheel
  • Callaway header/cat exhaust system with straight-through center exhaust
  • Dymag magnesium wheels
  • Bridgestone RE71 tires
  • Callaway coilover suspension, dual-adjustable
  • HD front and rear sway bars
  • Brembo Billet Indy Brakes (front and rear)
  • Connolly full-wrapped interior with Wilton rugs
  • Four-point leather-wrapped rollbar
  • MORE PHOTOS

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