Corvette Grand Sport
Corvette Grand Sport
The Grand Sport Corvette made its first appearance early in the 1963 season in the C-Modified class with a production 360 HP 327 Fl engine in its lightened 2000 pound body. It raced the season as a “stock” appearing racer. The season finale was held at Nassau each year with a “no holds barred” week of races on the island where all the teams could compete against each other using all of the latest high tech performance parts that were otherwise banned from regular club racing.
When the Grand Sport Corvette made its appearance at Nassau, it looked as if it had been given a big injection of steroids. Flared fenders, hood scoops, wider wheels and tires, and other visible changes only touched the surface of the technological advances that were in these Grand Sports.
Under the hood of the Grand Sport Corvette was found an all aluminum 377 cubic inch small block with 58 mm side draft Weber carbs. These aluminum engines were of the second casting batch from Chevrolet’s Research and Development department. There were 12 of these aluminum castings made. They were identified by the single letter “A through “L” which was stamped on the traditional location on the passenger side of the engine block. This engine used in this Grand Sport Corvette is letter “F” in the series.
Jim Hall racing a Corvette Grand Sport at Nassau 1963
These all aluminum engines were shared with Jim Hall’s Chaparral, but his sports racers used smaller 48mm webers that were more suited to the RPM requirements of the unique automatic transmissions that were in these revolutionary racing cars. The Grand Sport Corvettes either annihilated the competition or won everything in sight that week at Nassau. Note the stripe on the nose. The teams were so confident with their wins, that preparation began for the 1964 12 hours of Sebring.
Roger Penske and Jim Hall shared driving stints in a newly painted white Grand Sport Corvette. This car was the most prepared car of the group. A pneumatic system was installed on the car which happened to be one of the earliest applications of an air driven jack device on any sports racer. This pneumatic jack system not only reduced pit stop times but also eliminated any damage to the fragile fiberglass body and tube frame that could so easily occur when changing tires.
The attention to detail paid off, for this Grand Sport Corvette finished 1st in its class! The ’64 season ended with the Nassau races once again.
Roger Penske returned with his white Grand Sport Corvette for what was to be his final week as a professional driver. Although the all aluminum engine performed well during the season, it was replaced with a 364 cubic inch iron block for its final hurrah at Nassau. The aluminum heads were retained as well as the Weber carbs. The iron block was chosen because it flexed less at high RPM, thus allowing the engine to produce more horsepower. The extra horsepower would be needed against the other “no holds barred” racers.
The Grand Sport Corvette was further lightened by removing the pneumatic jack system which brought it’s weight down to 1900 pounds! Though the lead in the race was initially held by a lightweight Cobra that was powered by a new 390 cubic inch all aluminum Ford engine, Roger was able to wear down that Cobra, pass it for the lead, and eventually get the checkered flag.
Roger took almost a year off from racing after acquiring a Chevrolet dealership early in 1965, but he would return, this time as a team owner. Late in ’65 he received a phone call from Zora Duntov, telling him that a racing version of the newly introduced 427 cubic inch Mark IV big block engine would be available to select individuals. It was to be called the L88. Zora promised that he would take care of the homologation papers and Roger soon took delivery of the first factory produced L88 Corvette. Roger also acquired the last two Grand Sport Corvettes from Duntov shortly after that. They had been converted to convertibles as a test to reduce lift and wind drag at high speed. It was Roger’s idea to install the new L88 into these drag reduced Grand Sport roadsters and race them one more time at the 12 Hours of Sebring 1966.
Corvette Grand Sport with 427 L88 power at Sebring 1966
One Grand Sport Corvette was chosen, the L88 was installed, the pneumatic jack system which was used two years earlier, was installed, and larger wheels and tires were installed. Roger felt that this setup would be enough to keep up with the 7 liter Ford Mark II GT40’s. Due to the limited preparation time and no testing time, only estimates could be made in regards to tire size and spring rates. The Winters snowflake casting aluminum heads on the L88 were replaced with cast iron cylinder heads for the actual race ONLY because these iron heads could be ported much more aggressively than the new aluminum heads, which were much more porous than anticipated. During the 1966 12 Hours of Sebring, this Grand Sport Corvette did compete competitively with the GT40s, but it failed to finish after it was forced off the track by a slower car.
After the race at Sebring, the other Grand Sport Corvette was passed to a friend of Roger Penske, George Wintersteen. George was able to fine tune the Grand Sport roadster with the proper springs and tires. It was powered by a TRACO aluminum headed 427 L88 engine which performed quite well against the mid engine sports racers it was forced to race against.
Unfortunately, the Grand Sport Corvette was now without a doubt outclassed by the rapidly evolving mid-engined Lolas and McLarens that it was forced to compete against. Had the Grand Sport been available in this final form back in 1964, it could have possibly even beaten these mid engine prototypes. The owners of today’s Corvettes can thank the individuals involved with the Grand Sport Corvettes for the technology that they now take for granted. Wide tires, great suspension geometry, all aluminum engines, etc. can all be traced back to 1963, when the Grand Sport underwent it’s metamorphosis into a muscular sports racer.
Corvette Grand Sport at Vintage Race in 1987
The photo of the Corvette Grand Sport shown above was taken in 1987 during a vintage auto racing event. The owner of the Grand Sport regularly raced against a wide variety of sports cars including Shelby Cobras. This owner was joking around when he applied a similarly styled fender stripe to those found on the Shelby Cobras for this event. These fender stripes were originally designed by Pete Brock of Shelby American. These Brock designed fender stripes were applied to their competition Cobras so the Shelby team could identify which Cobra was racing past the pits by the color of the fender stripes, as the high speed of the cars made it difficult to read the number on the side of the cars. Pete Brock would again design a similar fender stripe technique with his BRE Datsun racing team of the late sixties and early seventies.
Please note that of all the historic Corvette Grand Sports, stripes were never placed on any of the fenders, the only time a stripe was used was at Nassau 1963, and these stripes were placed on the nose of the cars as shown in this post.
Dr. Pete Gimenez