In 1963, the original Grand Sport Corvettes made their first appearance early in the racing season in the C-Modified Class with an RPO production Z06 race package that utilized the stock L84 327/360hp engine. It also came with special finned-aluminum brakes, a 36-gallon gas tank (later deleted), a four-speed, cast-aluminum wheels (later deleted), a stiffer suspension, and heavier shocks. GM sold several of these cars to proven race teams to see what the car could do. This factory Z06 option demonstrated the potential of the Corvette in competition, but unfortunately two deficiencies in the Z06 option were revealed. The production Corvette was too heavy and the excess weight compounded the ineffective drum brakes on the car.
Chevrolet Engineering had an answer: A series of five Corvette race cars would be built using lighter-weight body materials, four-wheel disc brakes, a four-wheel independent suspension, and a big V-8 to complete the package. These Grand Sport Corvettes were to be designed and built in secret. The Corvette's main competition would be the Shelby Cobras, and, with Zora Arkus-Duntov's guidance, Chevrolet transformed a basic production pleasure vehicle into a competitive race car. As part of the conversion process, the car's "birdcage" was replaced with a tubular chassis, transparent lightweight fiberglass was bonded to the chassis, and stamped-steel wheels replaced the original cast-magnesium units. The steering box and differential were also cast in aluminum to save more weight. After the cars were prepared, Chevrolet submitted a homologation application to the FIA so the cars could be cleared to race.
In December 1962, Duntov took Grand Sport No. 1 to Sebring for testing. Since the 377ci engines were not yet fully developed, the car used a modified L84 327 engine for the tests. The car had some braking problems (eventually, vented rotors were applied to the cars), but due to the car running within seconds of the track record, the trip was deemed a success. Soon, GM brass found out about the Sebring tests and the FIA application was withdrawn, thus following the 1957 AMA anti-racing rules to the letter.
Since GM racing activities were at a standstill, GS No. 3 was loaned to Dick Doane, and GS No. 4 to Grady Davis for SCCA racing events. Their results were mixed, primarily due to a lack of factory support. After many modifications, Davis, with Dr. Dick Thompson, was able to win with GS No. 4 at the Watkins Glen SCCA event in August 1963. Both cars were returned to Chevrolet in October 1963. Then, Grand Sports No. 3, No. 4, and No. 5 were modified to reflect what had been learned over the last year of racing. Vents and slots were installed in the body, and new wider wheels and tires were fitted to the cars. Under the hood, the car carried the special all-aluminum 377ci small-block with 58mm side-draft Weber carburetors. Rumor has it these engines produced in excess of 485 hp at 6,000 rpm. Plenty of power, to say the least.
In December 1963, three of the Grand Sport Coupes (Nos, 003, 004, and 005) were shipped to Nassau, Bahamas, for the annual Speed Week. The two Grand Sports that were entered in the Tourist Trophy race on Sunday qualified well-Second and Third on the grid-but both dropped out during the race with overheated differentials. A "vacationing" GM engineer, who just happened to be carrying some in his luggage, later provided differential coolers. They were fitted to the three coupes in time for the Governor's Cup race on Friday. With the new diff coolers in place, the Grand Sports responded well. In Friday's race, the Grand Sports finished Third, Fourth, and Sixth, well ahead of the Cobras. Two Grand Sports entered the final race of the week, Sunday's Nassau Trophy, and finished Fourth and Eighth, again leaving the Shelbys far behind. When the crew returned to the States, the engineers worked to solve the remaining problems uncovered in the Nassau Speed Week events. Air-pressure buildup in the engine compartment of the Grand Sports had required the hoods to be taped down to prevent their exodus. This underhood pressure, combined with the large frontal area and high profile of the coupe body, also created the tendency for the cars to lift the front end at speed. In preparation for the Daytona endurance race in February 1964, the GM engineers converted Grand Sport coupes 001 and 002 to roadsters by removing the roofs to reduce their profile and frontal area. Special louvered hoods were also fitted to relieve the engine-compartment pressure problem.
Unfortunately, these modifications proved to be the last applied to the Grand Sports by Chevrolet Engineering. The Nassau successes and the publicity surrounding the affair again brought the Grand Sport project to the attention of General Motors' corporate brass. As in the past, the brass disclaimed any corporate involvement in racing and ordered the cars destroyed. Insiders at Chevrolet immediately whisked the three coupes off to private hands, where they had modest racing success in later years. The two roadsters remained hidden in Warren, Michigan, for years, but they occasionally surfaced for rare car-show appearances before being sold to Penske in early 1966. All five original Grand Sports still exist to this day in private hands.
Fast forward 30 years: In 1996, the new C5 Corvette was waiting in the wings, ready to change the way many of us feel about the Corvette from that point forward. The last couple of years of C4 production totals continued to slip, as the '97 model year grew closer and closer. Many people in the GM "decision loop" were worried the upcoming C5 could hurt the remaining C4 sales effort.
In 1996, Chevrolet released two new models to try to boost the last model year of the C4, and the Corvette Collector Edition was one of those new models. It was offered in either coupe or convertible and carried a retail price of $1,250. For that, you basically got a special coat of Sebring Silver paint, a leather interior (black, red, or grey only) with the Collector Edition logo embroidered on the headrests, and the five-spoke special rims. A total of 5,412 Collector Edition cars were eventually built.
The second special model released was the '96 Grand Sport. How the Grand Sport was conceived and brought to production is unique. Supposedly, the Corvette design team wanted to pay tribute to the end of the long-running C4 body style. The idea to do a specific Grand Sport commemorative model is currently credited to Chief Designer John Cafaro. In 1993, the team created the design test mules for the new Grand Sport and eventually showed it to a group of dealers who were part of a focus group that helped Chevrolet set future brand direction. This group responded that the GS design was too bold for production, and the initial sales forecast was in the 500-1,000 range, a low figure indeed. From a corporate standpoint, this was not enough sales to justify a special car like the GS. Then John Heinricy (current director of the GM Performance Division and past C5-R driver) came into the picture. At the time, he was the assistant chief engineer on the Corvette team. Essentially, he was at the helm of the C4 while Dave Hill was concentrating on the new C5.
According to Heinricy, while visiting the coffee pot one day he had a conversation with Dave Hill about overcoming the problem of the car's boldness and the probable low production totals. One of them said, "How about we have two special models? We'll make an unlimited number of commemorative specials and the limited-run GS." Supposedly, in that room on that day they set the total maximum number of Grand Sports at 1,000 (810 coupes and 190 convertibles were eventually built), since that's what the marketing department said they could sell. Eventually, the Collector Edition accounted for 25 percent of the total production in 1996, which remains the only model year in which GM released two different Corvettes.
From the beginning, everyone involved in the '96 Grand Sport project agreed the car should be about performance, not just fancy paint and interior. With the new '96 onboard diagnostics and the C5 coming out the next model year, constraints inside GM had to be dealt with. A completely new engine offering for the Grand Sport was out of the question because of the expense and time constraints. The eventual solution was to redesign the current small-block in the C4, the LT1, and offer it as a manual-transmission-only powerplant in all C4s, with the final engine being named the LT4. Beginning with the LT1, Chevrolet added larger high-performance aluminum cylinder heads, a bigger camshaft, bigger valves, a higher 10.8 compression ratio, roller rocker arms, and increased fuel flow via new fuel injectors. These changes resulted in 330 hp at 5,800 rpm. Red spark-plug wires, a red intake manifold, and red "Corvette" and "Grand Sport" lettering on the manifold and throttle-body cover completed the special engine.
Externally, the Grand Sport paid reverence to the Grand Sports from 1963. The car bore an Admiral Blue color with a wide white stripe covering the middle of the hood, roof, and rear portion of the body-the same colors carried on the Grand Sport driven by A.J. Foyt at the 12 Hours of Sebring in 1964. A pair of red hash marks was placed over the left front fender. This styling cue was added because, when the original Grand Sports ran at Nassau in the fall of 1963, three different tape colors were used on the front cowl to help identify them as they passed the pits at speed. Red was used on the '96 GS as a styling cue to tie the two generations together. Unique Grand Sport badging was placed on each side of the hood above the side-fender vents, as well as a unique chrome-plated Corvette emblem on the nose and gas lid.
All Grand Sport coupes used ZR-1-style five-spoke rims with 275-40ZR17 rubber on the front and 315/35ZR17 on the rear. With all this wide rubber on the car, GM had to find a way to make it legal by having it inside the wheelwells. Initially, the design team considered using the ZR-1 wide body for the GS, but reconsidered because they could upset the ZR-1 customer who paid a premium for the ZR-1 drivetrain and different body style. Then they decided to tuck some of the tread under the car by going to an offset wheel and using European flares already in the GM parts bin on the GS coupes. In fact, the Grand Sport wheels were the same as the '94-'95 ZR-1 five-spokes except they were painted with a glossy black finish and had the aforementioned 50mm offset rather than the ZR-1's 36mm.
The GS convertibles did not receive the fender flares and wider tires of the coupes. The wider tire/rim combination would not fit in a convertible (as a flat tire), so the convertibles were equipped with 255/45ZR17 in front and 285/45ZR17 in back to solve the problem. Interior color choices for the Grand Sport were limited to all black or a unique Torch Red and black combination, with red seats and trim and black carpeting. The Grand Sport name was embroidered on the seat headrests.
John Heinricy also had a key role in instituting the special VIN sequence for the Grand Sport. Since GM had done a special VIN for the '90-'95 ZR-1s, they established a policy banning the practice. John said he and others felt strongly about making the GS even more special and fought the powers that be at GM to make it happen. The only other Corvette to have had a unique VIN sequence was the '90-'95 ZR-1. Judging by the extreme enthusiasm for these special Corvettes demonstrated by groups such as the Grand Sport Registry, we think it's safe to say the '96 Grand Sport will stand out as a unique and rare Corvette icon in the decades to come.