Ford Authority

How Tape And Yarn Helped Hone The Original Ford GT40: History Alley

It’s a story you’ve likely read countless times before: Ford Motor Company, having been shafted in a business deal with Ferrari, decided to exact revenge on the Italian racing outfit by beating them at the legendary 24 Hours of Le Mans endurance race.

Ford’s tool to accomplish this task was, of course, the Ford GT40, but the race car didn’t start life as the Ferrari-slaying machine we now know. In fact, the Ford GT40 Mk I failed to leave much of a mark at all, after having been retired from both the Nürburgring 1,000km and the 24 Hours of Le Mans due to mechanical failures.

It was at this point, after the 1964 World Sportscar Championship season, that the Ford GT40 racing program was handed off to the late Carroll Shelby – a gigantic figure in American motorsports. Shelby, working with a team of engineers from Ford-owned aeronautic firm Aeronutronic, helped mold the Ford GT40 into its well-known Mk II form, transforming the car’s shape to recover power lost to aerodynamic inefficiency, and installing a 450-horsepower, 7.0-liter V8 in place of the old 4.7-liter unit.

But here’s something you might not have known: according to British website Car Keys, in order to uncover aerodynamic inefficiencies in the Ford GT40 Mk I’s design, Carroll Shelby et al. used tape and yarn. Yes, those two basic items you might have in your junk drawer as we write helped produce one of the most iconic performance cars of the last century. Shelby reportedly taped yarn to the driver’s side of the car so that he could see the direction of airflow firsthand while the car was in motion, which would go on to inform future decisions about how to best change the bodywork.

Testing with Aeronutronic also revealed that as much as 76 horsepower was being lost to poor air ducting alone, says Car Keys. By tweaking the design, and introducing a more potent motor, Shelby and his team managed to craft the Ford GT40 into a winning race car, earning an historic 1-2-3 finish at the 24 Hours of Le Mans in 1966.

It’s a fascinating story, and one that certainly warrants a good read. For the full scoop, check out

Aaron Brzozowski is a writer and motoring enthusiast from Detroit with an affinity for '80s German steel. He is not active on the Twitter these days, but you may send him a courier pigeon.

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