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Oct 30 2010

-From out of the past-
The Cheetah

The Bill Thomas Cheetah was a sports car car built from 1963-1965 by Chevrolet performance tuner Bill Thomas as a competitor to Carroll Shelby's Cobra.

In the late 50's, Thomas had tremendous success racing Corvettes and he gained the attention of influential men within GM. By 1960, Thomas had started his own company and he continued his chain of successes by making other GM products such as the Corvair and Chevy II run circles around the competition. In 1963, Thomas used his connections to gain covert support from GM (through the head of its Performance Product Group, Vince Piggins) to develop a concept vehicle.
The prototype was designed jointly by Thomas and his lead fabricator at the time, Don Edmunds. Edmunds is also credited with the bulk of the construction of the car. Financing for the project came from private investors including Thomas himself and John Grow, a Rialto, California Chevrolet dealer. In fact, the first car belonged to John Grow. Using his racing connections, Thomas arranged for material assistance from Chevrolet for the major components - specifically, the Corvette engine, transmission and rear-end assemblies.

Following delivery of the drive-train components, Edmunds laid them out on the shop floor and began taking measurements. With a few deft chalk lines on the floor, the basic outline of the chassis was determined. In fact, the original "blueprints" of the Cheetah consist of only a few simple drawings. This was Edmunds' trademark design methodology - sketch what he thought the car ought to look like, then build it. (The vast majority of the 600+ cars that Edmunds built in his career would be designed this way. Only his last few Indy cars would involve professional designers.) The bulk of the initial drawings show each major component drawn out in block form, with major dimensions marked. Given the basic chassis shape, Edmunds began sketching the body. Edmunds showed his drawings to Thomas and after a few minor changes, was given the green light to begin construction of what was originally meant to be a "Malt Shopper" - a cruising machine or styling exercise. Thomas wanted a prototype vehicle to show GM what level of work his company could do - all in the grand hope of winning additional contract work. Sometime after construction began, Thomas decided the car would also compete on the racetrack to further promote the concept. This midstream change in purpose was partly responsible for the chassis flexibility problems that emerged once the car began to compete on the racetrack.

Once Edmunds had the lower half of a rolling chassis built, he constructed a plywood body buck 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 off to California Metal Shapers and Aircraft Windshield Co. respectively. After the rough body arrived back at Thomas' shop, it was finished by Don Borth and Don Edmunds. A second car was also constructed with an aluminum body but the remainder of the cars were fiberglass. These fiberglass bodies were produced by two different companies - Contemporary Fiberglass and Fiberglass Trends. Note: It has been surmised by Thomas employees that the second aluminum car is the car that would eventually be sold to Chevrolet for evaluation purposes. It is also surmised that this is the same car that Thomas purchased back from Chevrolet to serve as a basis for the Super Cheetah, which was never finished.

The chassis was constructed of Drawn Over Mandrel (DOM) cro-moly tubing that was arc-welded. 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 differential without an intervening driveshaft. With the engine positioned in this manner, the driver's legs were beside the engine. For this to work, 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. Unfortunately, this design style also meant a very hot driver's compartment - an issue that would haunt the Cheetah on the track.

The racing history of the Cheetah is noteworthy in that despite the fact that the car suffered from the typical problems that plague any new project, the car won a number of races in 1964 in the hands of some capable drivers. Jerry Titus was a vocal advocate of the Cheetah as a contributing journalist for Sports Car Magazine; he would also drive the factory Cheetah race car in its early races. Another notable driver was Ralph Salyer who owned and drove the most successful racing Cheetah, in which he won 11 minor events between 1964 and 1965. His car was known as the Cro-Sal Cheetah, named for its mechanic Gene Crowe and Salyer. It is also became the only Cheetah roadster after Crowe cut the roof off to keep Salyer from suffering heat exhaustion due to the aforementioned heat buildup in the driver's compartment.

Besides cooking 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 racing (little triangulation was incorporated into the design). As a result, the vehicle 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, along with plates welded across the parallel bars of the trailing arms to stiffen them sufficiently.

Despite some initial evil 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. On the dragstrip, the car reportedly posted faster numbers than the much-vaunted 427 Cobra.

A fire in the factory destroyed the original plywood body buck, the factory drag car and some spare parts inventory, thus contributing to the eventual demise of the car. Another factor in the end of production was due to General Motors adherence to the automaker racing ban, thus killing backdoor projects like the Cheetah and the much-required parts supply. When the parts supply dried up, there was no way for Thomas to achieve the homologation numbers needed for racing, which went from 100 to 1000 units. Lastly, race car design was evolving and the true mid-engined configuration represented the wave of the future. To illustrate this point, in approximately the same time frame, Shelby's Daytona coupes were rendered obsolete by the GT-40.

The remaining original cars are left as highly desirable collector items. No official records are known to exist documenting the exact number of cars produced, but best estimates indicate as many as 29 cars were built to varying degrees of completion and configuration.

Bill Thomas died on 10 Oct 2009.

Copyright Don Edmunds©1993