When Ford redesigned the Mustang in 1967 to take the 390/320 HP big block V-8, Carroll Shelby took the next logical step and introduced the GT500, the first big block Shelby GT, powered by a modified Police Interceptor 428 CI engine rated at 355 HP. Buyers took to the new car immediately, and the car outsold its small block GT350 stable-mate 2,048 to 1,175 units. In addition to his partnership with Ford, Shelby was also the West Coast distributor for Goodyear, who in February asked Shelby to take part in a promotional event for its new Thunderbolt line of economy tires. Shelby judged that the GT500 would be the perfect choice for an extended high-speed demonstration of the new tire, but the decision took a twist when former Shelby American sales manager Don McCain approached Shelby with the idea of building a supercar that would outperform anything else in the world. Then employed by Dana Chevrolet in South Gate, California and Mel Burns Ford in Long Beach, McCain suggested that Carroll put a racing 427 in the GT500 for the test, let him sell the car and then build 50 more for Burns.

Ever one to leap at opportunity, Shelby instructed Fred Goodell, Shelby American’s chief engineer on loan from Ford, to prepare a GT500 with a special engine for the test, which would be held at Goodyear’s high speed test facility near San Angelo, Texas. Goodell selected GT500 number 544 for the task: “We rebuilt it with a special lightweight 427 racing engine; special rear axle, special transmission and, of course, Thunderbolt tires.” Don McCain later described the engine as “the mother of all 427s at that time…aluminum heads, aluminum water pump, forged crank, Le Mans rods, just basically everything inside the engine was built to run sustained 6,000 RPM – to race at Le Mans.” Essentially, it was the same powerplant used in the GT40 Mk II that had won the famous French endurance race the previous year, including a variation on the Mk II’s “bundle of snakes” exhaust system and its output of 600 horsepower. Goodell made other modifications to prepare the car for the tire test. An external oil cooler, braided lines and a remote oil filter were installed to increase the 427’s reliability; stiffer springs and shocks were mounted on the passenger side of the GT500 to counteract the high-speed cornering forces it would encounter on Goodyear’s 5-mile oval track. Goodell completed the car with one-off chrome inboard headlight surrounds and a unique version of the production Le Mans striping, with two narrow Blue stripes flanking a wide Blue center stripe, elements that distinguish it from all other GT500s.

Upon its arrival in Texas the last week of March, the Super Snake was fitted with Shelby 10-spoke aluminum wheels mounted with 7.75-15 Thunderbolt Whitewall tires, which were overinflated with nitrogen to keep the sidewalls rigid and prevent overheating. Before the test commenced, Shelby took a number of invited journalists, including the editors of Time and Life magazines, for demonstration laps around the track. Over the years there were conflicting claims as to who actually drove the car on its 500-mile test, but the story was set straight by Goodell during an interview for an episode of Speed Channel’s "My Classic Car." After the demonstration runs, during which Shelby reached a top speed of 170 MPH, Goodell recounted, “[Shelby] came back and he handed me his helmet and he says, ‘I’ve got to go to Washington, so you go ahead and drive the test. And so I got back in the car and I drove the car in the 500 mile test. We drove at 142 MPH average for 500 miles.” The test was a complete success: the skinniest tires ever mounted on a Shelby GT, the Thunderbolts had performed flawlessly, retaining 97 percent of their original tread. Read More