May studied engineering before turning to motorsport. In 1956 he and his brother Pierre entered the 1000 km of Nürburgring in a modified Porsche 550 Spyder. The car was fitted with an adjustable elevated wing mounted above the cockpit, engineered to generate downforce and improve braking and cornering speeds. During qualifying the modified 550 lapped the Nürburgring four seconds faster than the Porsche factory team's standard 550 Spyders — a striking demonstration of the device's effectiveness. Porsche racing director Huschke von Hanstein protested the wing, and May was not permitted to start the race with it installed. The episode identifies May as one of the earliest practitioners of aerodynamic downforce in competitive motorsport.
May made his Formula One debut in 1961 with Wolfgang Seidel's team Scuderia Colonia, driving a Lotus 18. He qualified thirteenth for the Monaco Grand Prix but was forced to retire with an oil leak. At the French Grand Prix he started twenty-second and climbed to eleventh at the flag. He was also scheduled for the German Grand Prix at the Nordschleife and participated in three non-championship Formula One events during the season. A crash in practice for the 1961 German Grand Prix ended his driving ambitions; May scored no World Championship points across his three championship starts.
Following his retirement from driving, May became a valued engineering consultant. During the 1960s he contributed to the development of a fuel injection system for Porsche. His work impressed Enzo Ferrari sufficiently that in 1963 Ferrari hired May to develop the fuel injection system for the Ferrari 158, the car that would carry John Surtees to the 1964 World Championship. May also persuaded Ferrari to adopt magnesium wheel rims on his racing cars.
Toward the end of the 1960s May developed a turbocharger conversion for Ford V6 engines that raised output from 108 hp to 188 hp. The engineering challenge was managing exhaust temperatures: turbochargers of the period were designed for diesel applications and could not withstand the higher exhaust heat of petrol engines. May's solution routed the exhaust from one cylinder bank through a long pipe looped around the engine, allowing the gases to cool before mixing with the hotter exhaust from the opposite bank, bringing the combined temperature within a range the turbine could tolerate.
May subsequently worked on high-compression engine design with a focus on fuel economy. His most widely noted contribution in this area was the reworked cylinder head — known as the "Fireball" head — developed for the high-compression Jaguar V-12 HE engine, which underpinned Jaguar's high-efficiency engine line.