The Bill Thomas Cheetah was an American sports car designed and engineered entirely with American components, and built from 1963 to 1966 by Chevrolet performance tuner Bill Thomas. It was developed as a competitor to Carroll Shelby's Cobra.
Bill Thomas William P. "Bill" Thomas was born on May 28, 1921, and lived in Anaheim, California. In 1956 Thomas commenced work tuning and modifying Chevrolet Corvettes for racing for C S Mead Motors Co. By 1960, Thomas had started his own company, Bill Thomas Race Cars. At that time General Motors approached him to undertake performance work on the new Chevrolet Corvair. He also prepared the 1962 409 Bel Airs and Biscaynes for drag racing and another Chevrolet stock car for Louis Unser who won its division of the Pikes Peak International Hill Climb. He was also contracted by GM to develop the Chevy II.Bill Thomas tribute, Bill Thomas Cheetah website, retrieved 22 May 2015
Bill Thomas died October 10, 2009.
Design and development
Prototype In 1963 Thomas gained covert support from General Motors Performance Product Group head Vince Piggins to develop the Cheetah as a concept vehicle. It was designed by Thomas and Don Edmunds, his lead fabricator. Edmunds is credited with the bulk of the construction of the car. Financing for the project came from private investors, Thomas, and John Grow, a Rialto California Chevrolet dealer. Grow owned the prototype car. Using his racing connections, Thomas arranged for material assistance from Chevrolet for the major components - the Corvette 327 engine, Muncie transmission, and independent rear-end assemblies. Other components were stocked from the larger GM parts bin, such as Chevrolet passenger car spindles, and NASCAR spec Chevrolet drum brakes.Cheetah Cars website history , retrieved 20 May 2015
Design and build Following delivery of the drivetrain components, Edmunds laid them out on the shop floor and began taking measurements. Using chalk, Edmunds sketched the basic outline of the chassis. The original blueprints of the Cheetah by Edmunds consisted of a few simple drawings showing the major components in block form, with major dimensions marked. Edmunds' design methodology for the majority of cars he built during his career was to sketch what he thought a car ought to look like, then build it. Only his last few Indy cars involved professional designers.
Once the chassis shape was determined, Edmunds sketched the body. He showed his drawings to Thomas and after a few minor changes, began construction. The Cheetah was designed to be a cruising machine or styling exercise, not a racing car. Thomas wanted a prototype to show General Motors the level of work his company could do with the intent to obtain additional contract work. After construction began Thomas decided the car would also compete on the racetrack to further promote the concept. The chassis had not been designed for this and therefore was not rigid enough for racing. This problem emerged once the car began to compete.The Cobra And The Cheetah: A Muscle Car Tale (Part Two), Ronnie Schreiber, September 8, 2010
Once Edmunds had the lower half of a rolling chassis built, he constructed a plywood body form or "buck" on which fit on top of the chassis. The buck included removable metal frames which showed the outline of the windows. Once completed, the body buck and forms were sent to California Metal Shaping for an aluminium body and Aircraft Windshield Co for the windows. Once returned to Thomas', it was finished by Don Borth and Edmunds. A second car was also constructed with an aluminum body in December 1963, for testing by the Chevrolet Engineering Center. The remainder of the cars were bodied in fiberglass.
Production models The production models used fiberglass bodies. The first were produced by two different companies - Contemporary Fiberglass and Fiberglass Trends. Contemporary Fiberglass was selected to produce the bodies following some problems with the Fiberglass Trends molds. Fiberglass Trends went on to produce their own version of the Cheetah under the name GTR, which was used for drag racing.
The Cheetah's chassis was constructed of Drawn Over Mandrel (DOM) cro-moly tubing that was heliarc welded (more commonly referred to as TIG or tungsten inert gas welding) using a P&H Mining DAR-200 welder. The design of the car was unusual in that it was front engined, but with the engine sitting so far back in the chassis that the output yoke of the transmission connected directly to the input yoke on the independent rear suspension's central differential "pumpkin" housing, basically making the driveshaft only a universal joint linking the transmission with the differential. With the engine positioned in this manner, the driver's legs were beside the engine. The exhaust system headers passed over the top of the driver's and passenger's legs. The tops of the footboxes were curved to make room for Edmunds' handmade headers. This design takes the attributes of what is known as an FRM layout to an extreme. Consequently, this design gave a front/rear weight distribution roughly approximating a mid-engined vehicle without the cost of an expensive transaxle arrangement. This design style resulted in a hot driver's compartment - an issue that would impact the Cheetah's performance on the track.
Super-Cheetah project Former employees believe that the No. 001 aluminum car sold to Chevrolet for evaluation and later repurchased by Thomas formed the base model for the "Super Cheetah" project. This prototype Super Cheetah was intended to become the new 1965 improved street Cheetah, which was also rumored that it was going to be raced at Le Mans. Work started on the Super Cheetah early in 1964, roughly within the same timeframe as Carroll Shelby's "Ferrari-focused" Shelby Daytona racing coupe. A 4130 chrome moly steel space frame was produced for the Super Cheetah, incorporating changes suggested by Chevrolet during its evaluations at Riverside with input from Bob Bondurant, Jerry Titus, and others from June 1963 to 1964. The redesign also incorporated changes learned from experience with racing the original Cheetahs.
The interior was widened for driver comfort with two more inches on either side of the foot pedal, the steering rack-and-pinion moved to rear steer position of the front spindles (unlike Bill's first design front steer position on the 1964 model), the front frame section had 7° caster built into it, the front shock tower area had new diagonal tubing installed to limit chassis flex, the front upper and lower a-arms had ball joints and the rear chassis area was enlarged to allow for more fuel capacity. The project was never finished by Thomas because of Chevrolet's decision to withdraw its support.Cheetah Cars website - race history , retrieved May 20, 2015
Racing history
Races, drivers, and owners Originally, the car was designed with Dave MacDonald in mind as the driver; Thomas and MacDonald had established a long-standing racing relationship in Corvettes. Carroll Shelby offered MacDonald the opportunity to drive the Cobra, which MacDonald accepted. However, MacDonald died on May 30, 1964, driving at Indianapolis.
The Cheetah was to debut at the 1963 Los Angeles Times Grand Prix but crashed in practice two days before with Don Horvath at the wheel. Its aluminium body was replaced by a fibreglass one. Its first event was at the Cal-Club, Riverside International Raceway event on February 1, 1964. It crashed at the end of the first lap with Jerry Titus at the wheel. A water hose had come off, spraying water under the rear wheels causing the car to skid off the track at the turn. Titus raced the car throughout the 1964 season. He was a vocal advocate of the Cheetah as a contributing journalist for Sports Car Graphic magazine. In 1965, Jerry Entin became the car's owner (race car number 58) and he raced it with some success. This car was used in the Elvis Presley movie Spinout.Cheetah cars - race history , retrieved May 20, 2015
The third car, the first fibreglass bodied, was sold to Ralph Salyer in 1964 and converted to a roadster. He raced it in 1964 Challenge Cup at Daytona. It was the most successful racing Cheetah, winning 11 minor events between 1964 and 1965. Salyer's car (race car number 25) was known as the Cro-Sal Cheetah, named after its mechanic Gene Crowe as well as Salyer. Crowe converted it to a roadster to keep Salyer from suffering heat exhaustion due to the problem of heat buildup in the driver's compartment from the exhaust pipes.
Bud Clusserath purchased the fourth car (race car number 46) for the same race. Allan Green brought the fifth car (race car number 17) for Jerry Grant to race in the Challenge Cup, but he crashed in practice.
The sixth car was also ordered by Alan Green Chevrolet of Burien/Seattle, Washington, and was built to racing specifications. It raced in the USRRC race series (race car number 15). Its outstanding documented racing record includes 10 Federation Internationale de L’Automobile (FIA) events in 1964-65. In 2009, this Cheetah received a FIA-issued Historic Technical Passport (HTP). The HTP makes this Cheetah eligible for any FIA-sanctioned vintage event in the world. This is the only Bill Thomas Cheetah to have a HTP. Alan Green Chevrolet took delivery of this Cheetah in March, 1964. It was raced extensively during the 1964 and 1965 seasons, usually under the Alan Green Chevrolet banner. Its maiden race, a California Sports Car Club event, took place at Pomona, California, on March 22, 1964. Although, it was delivered in red, it was repainted "Alan Green green", in approximately June, 1964.
The seventh car was also acquired by Allan Green, for his wife for normal road use.
The eighth car was not raced until more recently at vintage events by Skip Gunnell. Jack Goodman purchased ninth car the Dixon Cadillac (race car number 33) and after it was sold to James Phillips it was modified, winning the 1968 A/SR championship for the Southern Pacific Region of the SCCA in 1968. Don Grieb drag raced the tenth car.
Performance issues Besides heat impact on the driver, the engine was also prone to overheating, due in no small part to the failure to account for vents to draw hot air out of the engine compartment. Eventually, the overheating problems were solved by using a larger Pontiac NASCAR radiator, by cutting various configurations of holes in the hood and full-length belly pan and lastly by adding spoilers to draw the hot air out from underneath the hood (the first hood spoiler was actually a rope that ran across the hood from fender to fender.) Another major problem was due to the aforementioned mid-stream change in purpose for the vehicle; because the car was originally designed as a proof-of-concept, the chassis lacked the rigidity necessary for road racing (little triangulation was incorporated into the original design). Under changing loads such as those experienced on a twisting road course, the vehicle's suspension geometry continually changed and proved difficult to handle, even for experienced drivers such as Jerry Titus. Adding power only aggravated the problem; under hard acceleration, the trailing arms could bow outwards, allowing the rear wheels to toe in. Owners of the car were able to improve handling by adding gussets and triangulation to the chassis, modified (or completely re-engineered) trailing arms and disc brakes.
Despite some adverse handling tendencies on road courses, few cars could catch it in a straight line due to its Thomas-built 377 cu in (6.2 L) displacement, dual air-meter, fuel-injected Chevy small-block V8 based engine.
Demise