This June marks a golden anniversary in Corvette lore: fifty years ago, the first Chevy sports cars took on the epic challenge of racing twice around the clock at LeMans. Three privately prepared cars were entered by the wealthy American sportsman Briggs Cunningham and one driven by John Fitch and Bob Grossman scored fifth place in the GT class with an eighth-overall finish and a average speed just under 98 mph. Crashes and an engine failure sidelined two of the Cunningham Team cars but a fourth 1960 Corvette fielded by Lloyd Casner’s Camoradi team was tenth overall.
Success at LeMans was a huge leap forward for an American sports car especially since the Automotive Manufacturers Associations ban on direct factory participation in motorsports was in force. However, the ban didn’t inhibit key Corvette personnel, including Zora Arkus-Duntov, from lending a hand during preparation at the Cunningham-Momo shop at Long Island, New York.
Later in the 1960s and into the seventies, other teams took their turn with Corvettes at LeMans but with less success. Entries fielded by Dick Guldstrand, Scuderia Fillipinetti, and John Greenwood were impressively quick in qualifying but distinctly lacking in longevity. Finally, another Corvette top-ten finish was achieved by Reeves Callaway in 1995 with a ninth overall and second in GT classification.
Fast forward to the 21st Century. A full factory effort campaigned by Pratt & Miller Racing began in 2000 with a race-prepped C5 Corvette for the GTS class at LeMans. Results came quickly. Corvettes finished third and fourth in class in the first run and by last year, the fleet of 12 C5Rs, eight C6Rs, and one intermediate C5-6 racer constructed by P&M had racked up an impressive string of LeMans finishes: 6 GTS or GT1 class victories, plus another 10 podium finishes.
In addition, the Corvette Racing effort absolutely dominated the American LeMans GTS and GT1 categories by scoring 77 class victories and a total of 26 driver, team, and manufacturer championships during the past decade.
Then, suddenly, this steamroller switched paths. After last summer’s LeMans class victory, the Corvette GT1 racers were parked (and subsequently sold), and a new campaign commenced one class down in the GT2 category. The main reason for the change was that Chevrolet had nothing more to prove and no real competitors in the GT1 game. Also, GT1 and GT2 merges into a single GT category at LeMans this year.
The good news is that this program, along with NASCAR, survived GM’s quick bankruptcy rinse. Pratt & Miller Racing boss Doug Fehan is quick to point out why: because even the witless government financial experts could see that racing Corvettes have delivered a valuable return on investment; because there are 800-million pairs of eyes that watch some portion of the 24 Hours of LeMans every year; because Chevy is a global brand and the success of its racing flagship casts a warm glow over the entire bow-tie product line; and because there is genuine technology transfer — a true two-way street — between Corvettes plying the street and those that live on the track.
Diving into the deep end against well established GT2 competitors last year, the Corvette team made its intentions known with second and fourth place finishes in the first race at Mid-Ohio. When the season ended at Laguna Seca, the record showed one victory at Mosport and five podium finishes. Four Corvette drivers tied for sixth and 11th place finishes in the driver’s points race. Chevrolet finished fourth in the manufacturers’ championship and Corvette Racing scored sixth on the team championship list, an excellent finish for contesting only half of the 2009 GT2 races.
The 2010 series begins on March 20 with the 58th edition of the 12 Hours of Sebring. Two Pratt & Miller factory Corvettes will face 12 GT2 competitors fielded by eight other teams and representing five other manufacturers: BMW (M3), Ferrari (F430), Ford (GT), Jaguar (XKR), and Porsche (911 GT3 RSR).
To find out to what extent the outgoing Corvette GT1 differs from the new wave GT2, we recently visited Pratt & Miller in New Hudson, Michigan. The short answer to the ‘what’s the dif?’ question is virtually every nut and bolt. There are no parts shared between the GT1 and GT2 Corvettes.
The rules drive most of the changes. Since carbon-carbon brakes and forged magnesium wheels are not permitted, the 2010 GT2 Corvettes are now equipped with cast-iron brake rotors and aluminum wheels supplied by BBS.
Racing’s attempt to seem green has also prompted a major change in engine design. Replacing the 7.0 and 6.0-liter LS V-8s used previously is a 5.5-liter version of the same engine with smaller bore and stroke dimensions. Breathing through two 28.8-mm diameter intake air restrictors, the advertised horsepower is 485 at 5800 rpm which is not a whole lot more than a base Corvette’s 6.2-liter V-8 delivers.
In addition to the necessary brake and wheel changes mentioned previously, the GT2 Corvette racer is based on a ZR1 so this also marks the shift to a space frame made of hydroformed aluminum versus the outgoing steel structure. To attach the steel-tube roll cage mandated by the rules, Pratt & Miller engineers created special anchors that allow a steel spigot to be bolted and glued to aluminum sockets. The resulting corrosion- and stress-resistant joint is used as a welding point for the cage at eight well spaced locations.
In addition to the aluminum space frame, several other production ZR1 components make the leap to the race car with appropriate alterations. That list includes the entire windshield frame including A-pillars and the windshield itself; the steering system including the rack-and-pinion gear, adjustable electric power assist, and a tilt steering wheel; certain brake cooling details; and the behind-the-driver location for the fuel tanks.
GT2 rules also require a close allegiance to the production bodywork (though all panels are made of carbon fiber moldings instead of the production mix of carbon fiber and fiberglass). There are seven permissible deviations: front air inlets in the fascia, front fenders with flares for wider racing tires, a cooling-air exit duct in the hood, blended rocker panels, rear fenders with flares, NACA ducts in the rear deck air to admit transaxle and brake cooling air, and a rear-mounted wing. Compared to the GT1 wing design, the cord (longitudinal dimension) is reduced by 25-percent — from 15.7 inches to 11.8 inches.
Another notable change is to the minimum weight allowed by the rules. The Corvette GT2Rs must weigh 2745 pounds with all fluids except fuel versus the GT1’s 2580 pounds. Up to 77 pounds of ballast is permitted to help lower the center of gravity and to adjust the front-rear weight distribution.
External body dimensions are for the most part unchanged. The 18-inch Michelin racing tires mounted to 12.5-inch wide front and 13.0-inch wide rear wheels are also the same as what was used in GT1. The telemetry system linking the race car’s electronic systems to the pits is no longer permitted. Aerodynamic changes yielding less down force include a notably smaller front splitter and a rear diffuser that’s both shorter in length and lacking the longitudinal strakes and side fences. The Xtrac transaxle, which offers rapid clutchless sequential shifts and six forward speeds, is one of the rare parts transferred from GT1 to GT2.
The change in power-to-weight ratio is a significant 30-percent. Factor in the less effective brakes, heavier wheels, and the reduction in aerodynamic down force and you’ve got a package with notably less speed potential. That said, until the green flag drops, no one can accurately say how the new Corvette’s will stack up against the Porsches, Ferraris, and BMWs that prevailed last year. Pratt & Miller’s confidence rests on the powerful simulation tools which predict that this effort will be in the competitive thick of things.
One final note to all the wealthy swells in the reading audience tempted to don Nomex in order to try their hand at GT2 racing: Pratt & Miller will happily sell an exact match to the two cars they’ll be racing this year. The list price of $750-800,000 covers a turn-key car that’s been thoroughly shaken down at the track. A transporter, pit crew, tools, spares, and the requisite deep-pocket sponsor are not included. While this figure is roughly one-third higher than the price of a new 911 GT3 from Porsche, less expensive spares and the fact that no upgrades are required to match the factory team’s performance brings the two rivals into parity from an operating-cost standpoint.
If, instead, you’re just curious how the Corvette GT2Rs fare this season, plant your face to the television to watch the Sebring checkered flag fall at 10:30PM on March 20.