John Greenwood's Wide-body Corvettes
After back-to-back SCCA championships in 1970 and 1971, John Greenwood and brother Burt set out designing and building faster and better handling racecars. The cars were constructed for endurance racing in both SCCA and the newly-formed IMSA competition, and were based on the full-frame third-generation Corvette. Several cars were built over the next few years, with the same cars often appearing in different guises. These cars introduced not only the wide-body race design, but also a cross-ram fuel injection system, coil-over suspension, and other minor innovations.
The original chassis work was done by Ron Fournier, who has also worked with Roger Penske, A.J. Foyt, Bob Sharp Racing, and others. Front coil-over suspension housed 11 x 15 inch wheels, with huge 17 x 15 inch wheels at the rear. In place of the production Corvette's transverse leaf spring, the rear suspension was independent with coil springs using unequal-length upper and lower A-arms. To achieve a low front nose, the body was dropped around the frame. Goodyear Blue Streak racing tires were used, with 24.5 x 10-15 at the front and 28.0 x 17-15 in back.
To contain the wider wheels and tires, fender flares were developed with help from Zora Arkus-Duntov, as well as Jerry Palmer and Randy Wittine. The interior contained a single bucket seat, fire extinguishing system, and tube-type roll cage to add chassis stiffening. A full array of gauges included volt meter, fuel pressure, oil pressure, oil temperature, coolant temperature, rear-end temperature, and a 10,000-rpm tachometer.
The larger-than-stock disc brake rotors were drilled, not so much to improve cooling, but because Greenwood felt it helped improve brake response. Dual master cylinders had a balance bar that allowed front/rear brake bias to be varied. With a race weight of about 2900 pounds, the Corvette was considerably heavier than the competing Porsches, BMWs and Monzas, but the 700+ horsepower motor and aerodynamic body helped even the odds.
Big-Block Chevy Power
The power of John Greenwood's Corvettes started with Chevrolet's big-block ZLI motor. The 454ci aluminum block received a .60-inch over-bore, giving a displacement of 467 cubic inches. The bottom end featured Carillo rods, a modified Chevy crank, and Weaver dry-sump oiling system. Pistons and cylinder heads were Chevrolet.
Isky supplied the timing chain and roller rockers and a General Kinetics camshaft was used. For better weight distribution and fit, the engine was relocated approximately 1-1/2 inches to the right and back about 12 inches.
Greenwood attributed his engine's great power (700 horsepower at 6,800 rpm, peak torque 620 lb-ft at 4,000 rpm) to the unique fuel injection system, which used a cross-ram magnesium manifold with fuel cooler built into the bottom. The induction system used Lucas injection components and provided a smooth and flat torque curve.
A handmade radiator was used and placed vertically for improved cooling. Coolers were fitted to the engine, differential and transmission. Four-inch exhaust sidepipes exited out of the bottom of each door.
Backing up the power was a Muncie M22 four-speed transmission. Final drive ratio was 2.73:1, and with 28-inch tall rear tires, allowed top speeds over 220 mph.
Greenwood debuted the wide-body #48 Corvette at the Detroit Auto Show in January 1974. Aside from competing in SCCA and IMSA events, the car was also used as a "test-mule" for ongoing chassis development, as well as a model for customer cars.
1974 Race Season
The first competitive outing for the Corvette wide-bodies was at Road Atlanta in 1974. The race was a 10 lap winner-take-all event. Greenwood came in first with a 20-second advantage over 2nd place finisher Bobby Allison, who was driving a Big-block Camaro. Throughout the '74 race season, the Corvette proved fast if not reliable. In July, the third and final round of the SCCA Trans-Am Championship series was held at the Road America raceway in Elkhart Lake, Wisconsin. Greenwood set a new qualifying lap record, and led the race for 14 laps before experiencing engine failure. The IMSA Talladega race in August was won with Greenwood's Corvette driven by Milt Minter.
The IMSA GT race finale was held at Daytona International Speedway in December of 1974. Greenwood brought a new car to the 250-mile event, recording speeds of over 210 mph. This was well over the GT standards of the day. He won the race with a 33-second margin over 2nd place driver Al Holbert. Not surprisingly, the following race season saw the Porsche and BMW race teams adopt the flares and open wheelwells of the Greenwood Vettes.
1975 Race Season
Early in 1975, John and Burt started experimenting with rear-mounted coolers, ducts cut into the door panels, and feed tunnels in the rear fender extensions. Two new full-frame cars were seen, now fitted with a "smaller" 427ci (7.0L) engine. Although reliability problems plagued the team during the 1975 season, Greenwood won three Trans-Am races and the SCCA Championship. At the Pocono race in June, Greenwood started in last place due to switching drivers after qualifying. He ended up winning the race and setting a new fast lap record. Round 3 of the SCCA Trans-Am Championship was held at Portland International Raceway. Greenwood won and set a new fast lap record. The 4th round was held at Nelson Ledges Road Course in Garrettsville, Ohio. Greenwood led the entire race, and set a fast lap record.
1976 Le Mans
Greenwood was invited to participate at the Le Mans 24-hour endurance race in 1976. Adorned with an American flag paint scheme, the #76 "Spirit of Le Mans" Corvette qualified on the pole. Driven by Greenwood and co-driver Bernard Darniche, the fuel-injected big-block Corvette ran extremely fast, seeing speeds of over 210 mph down the famed Mulsanne Straight. Unfortunately, a split fuel tank put them out of the race with a DNF.
The 1976 season marked an end to full-frame race cars in SCCA and IMSA. New rules introduced for 1977 permitted tube-frame chassis and significant modifications to traditional suspension layouts. It brought about a new era in endurance racing.
John Greenwood's contributions greatly added the Corvette's legacy as America's Sports Car. In addition to his podium finishes, he scored 11 IMSA pole positions against the German factory teams. His cars had always been thoroughly prepared and very fast, and the wide-body Corvettes were always crowd favorites. On his successes, Greenwood said,
"You know that a lot of the equation was the big engines. I had learned on Woodward Avenue that you don't want to get left behind on the straight parts."
Pictures Courtesy Fred Lewis Photos
back to Motorsports page