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Corvette Racer Kits to the Mighty C7 ZR1 … How Did We Get Here?

The Illustrated Corvette Designer Series No. 258

Jul 24, 2018
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Bowling Green has cranked out a new ZR1 and buyers are not shy about using the full potential of Chevy’s latest, greatest Corvette supercar. YouTube has hundreds of videos of ZR1s drag racing, street racing, road racing and on dynos. Sure, some C7 ZR1s will get put away and saved for easy sunny-day driving, but the times, they are definitely a-changing.

The C7 ZR1, Z06 and Grand Sport are high-octane, loud, in-your-face performance cars, and aren’t the only ones; Ford and Chrysler also offer stout street cars and brutes of their own. Some have speculated that we are experiencing the last hurrah of the big internal combustion engine-powered performance cars. Hybrid supercars are already here, so it will only be a matter of time until we look back on this time as the Golden Age of Performance Cars. The “muscle car wars” supposedly ended in 1970, obviously not so. So, how did we get here? Racing!

In the early 1950s, there were almost no safety rules in auto racing whatsoever. Consequently, auto racing quickly became a blood sport, with drivers and sometimes spectators dying weekly at racetracks. The objective of the infamous 1957 AMA Racing Ban sought to distance manufacturers from this new public menace, but it was a “gentleman’s agreement” with no teeth. Ford and Chrysler quickly abandoned the agreement. Pontiac went NASCAR racing anyway, and Chevrolet hired Vince Piggins to establish their backdoor NASCAR racing program. Meanwhile, Ed Cole assigned Zora Arkus-Duntov and engineer Mauri Rose to develop and implement the RPO “racer kit” program with help from Smokey Yunick. By 1999, 42 years later, it was a whole new world. Pratt & Miller had become Chevrolet Engineering’s defacto Racing Engineering division, with base Corvettes, Grand Sports, Z06s and ZR1s all reaping the benefits.

ICS 258 Racer Kits To ZR1 2B 2/3

The first racer kit arrived in mid-1957, but you had to know what to look for in the parts catalog, not the sales brochure. RPO 684 was the “Heavy Duty Racing Suspension” option that included heavy-duty front and rear springs, stiffer shocks, larger front stabilizer bar, quicker steering, metallic brake drum facings, finned brake drums with front and rear scoops and fresh-air ducts for the rear brakes. Mandatory with RPO 684 was Positraction, four-speed transmission, and the 270hp or 283hp 283 fuel-injected engine. (Sounds like a Z06, doesn’t it?) The complete package cost around $1,750 on top of the $3,167 base price, for a total of $4,917; as much as a Cadillac Biarritz.

By the end of the ’50s, thanks to the racer kits, Corvettes were a force to be reckoned with in SCCA racing. The new, 1963 Sting Ray’s racer kit was RPO Z06 that had the same formula used on the C1 racer options; suspension and brake upgrades combined with the top-of-the-line Fuelie engine. Unfortunately for the early Sting Ray racers, SCCA had Corvettes and Cobras in the same class, with Corvettes at a major weight disadvantage. RPO Z06 was only available in 1963, with 199 cars built. But from 1964-’66 the same basic Z06 parts were offered as individual RPO parts, the complete package simply wasn’t called RPO Z06. These cars “could” be driven on the street, but few were because the suspensions were so harsh and offered no advantages for street Corvettes.

The racer kit that turned the Corvette’s fortunes was the arrival of RPO L88 in 1967. The suspension setup was similar to the previous racer kits, but the L88 was not streetable and only useful for high-speed racing. To discourage buyers from checking off the engine option with the biggest horsepower figure, Duntov deliberately had the official rating set at 430 hp, five horsepower less than the barely streetable 427/435 L71 Tri-power. L88 Corvettes also had no radiator shroud, making them impossible to use in stop-and-go traffic.

The common denominator with all of the racer kit Corvettes is that they were totally void of any unique branding. As delivered, they looked like any standard Corvette, with the exception being the C1 racer kits that came with chrome button hubcaps instead of the full hubcaps. The overriding reason for this was that Chevrolet “officially” did not endorse racing. The backdoor racing certainly added to Chevrolet’s mystique, but in hindsight, GM let Ford and Chrysler feast on racing glory.

It is fun to imagine what a special model C1, racing-inspired Corvette might have looked like; they certainly had the parts to make it happen. Perhaps a Sebring Special fuel injected with dedicated Halibrand-style racing wheels, a little bit of racing trim, and center stripes. Or a Daytona Grand Sport C2 Sting Ray with the styling elements of the Grand Sport, combined with the Z06 suspension and fuelie engine. Or how about a street version of the 427 L71 C3, with L88 fender flares and hood, factory side pipes and American Racing five-spoke wheels? It could have been so cool.

ICS 258 Racer Kits To ZR1 3B 3/3

The L88 officially went away after 1969, but the L88 and the all-aluminum ZL1 engines were still available through the Chevrolet Parts Catalog for many years. The last racer kit option was the Randy Wittine-designed “widebody” that IMSA racers John and Burt Greenwood made famous. Imagine if that had been made into a special model C3 Corvette? The closest we ever got to see that concept came from the Greenwood Brothers’ Sebring GT, Turbo GT, Daytona, Can-Am and GTO Corvettes.

The C4 generation is an interesting story. When the ’84 Corvette arrived the press and the public went wild. Subsequent Corvettes got so good that today, an ’84 Corvette can be had for as little as $4,000. The first official “performance model” Corvette ever offered was the 1990 ZR-1, but it was a $27,016 option on top of the $31,979 base price. All totaled, from 1990-’95, 6,922 ZR-1s were built. The ’96 Grand Sport with the final version of the classic small-block Chevy engine, the 350 LT4, was a primer for future, out-in-the-open performance Corvettes.

The breakthrough performance model Corvette was the ’01 Z06. The car became an instant classic, but a closer look reveals that the Z06 used the same racer kit formula: suspension, brakes and tires improvements, combined with the strongest engine available—the LS7, a hot rodded LS1. A break from the old formula was that the new Z06 had a distinctive look with its fixed roof coupe body, side rear brake scoops, dedicated wheels, mesh grille inserts and badging. There was some loose talk of the Z06 using a street version of the C5-R’s racing body, which would have been very cool, but most likely too expensive.

As the C5-R Corvettes racked up wins, championships and three class wins at Le Mans, lessons learned were poured into the C6 Z06 that spilled over into the ZR1 and Grand Sport. The Corvette Racing Team’s “Jake” mascot now adorns many production Corvettes. The C6.R racing Corvettes helped develop the C7 Z06 and ZR1. Never before have we seen so much racing-inspired hardware proudly displayed on production Corvettes. In the old days, racing goodies were all hidden; “hush-hush.” Today, they are in-your-face, screaming at all opponents, “Come on! Jake and I dare ya! And we take no prisoners!” We are indeed in the golden age of internal combustion performance Corvettes.

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