The company traces its roots to 1903, when Jens Stroyer and Horace Pelham Lee established a joint venture called Lee Stroyer. Renamed Coventry Simplex in 1905 after Stroyer's departure, the firm supplied engines to early motorists and provided generators for searchlights during World War I. In 1919, Pelham Lee acquired a separate company and renamed it Coventry Climax Engines Ltd. Through the 1920s and 1930s, Coventry Climax supplied engines to a broad range of light car manufacturers and diversified into commercial vehicle engines and mobile fire pumps. The fire pump division became particularly successful and would prove pivotal to the company's later racing involvement.
In 1950, Harry Mundy joined Coventry Climax and collaborated with Walter Hassan on a new lightweight all-aluminium overhead camshaft engine in response to a government requisition for a portable fire pump. This Featherweight engine — the FW — attracted attention at the London Motor Show from Colin Chapman and others in the racing community. Management concluded that success in competition could boost the company's profile, and the FW was adapted for automotive racing as the FWA.
The FWA first appeared at the 1954 24 Hours of Le Mans in a Kieft sports racer. Its popularity in sports car racing led to the larger FWB, which approached 1.5 litres, suiting the then-current Formula Two regulations. By 1957, Climax engines began appearing in Formula One in the rear of Cooper chassis. Stirling Moss scored the company's first Formula One victory in Argentina in 1958 using a two-litre version of the FPF four-cylinder engine.
The FPF was a double-overhead-camshaft all-aluminium four-cylinder conceived as half of an earlier unraced V8 project designated the FPE. Beginning as a 1,475 cc Formula Two engine, it was progressively enlarged for Formula One competition. A 1,964 cc version took Stirling Moss and Maurice Trintignant to Cooper's first two Grand Prix victories against 2.5-litre opposition in 1958. A full 2,497 cc version enabled Jack Brabham to win the World Championship of Drivers in both 1959 and 1960 driving Cooper-Climaxes, marking the moment when the rear-engined mid-engined layout definitively supplanted the front-engined configuration in Formula One.
When the regulations changed to a 1.5-litre formula in 1961, a smaller version of the FPF won three championship races. The larger variants were subsequently used in Tasman Series and Indianapolis racing, and in Australia the 2.5-litre FPF was actually manufactured under licence by Repco.
The 1.5-litre FWMV V8 was developed from the smaller FWMC racing engine by using a V8 configuration derived from its inline-four architecture. It ran for the first time in May 1961 and debuted in competition at the 1961 German Grand Prix in a Cooper. After resolving early overheating problems caused by differential thermal expansion between steel cylinder sleeves and aluminium cylinder heads, the FWMV began winning regularly from 1962.
A significant development came in 1963 when Coventry Climax adopted Lucas fuel injection with sliding throttle plates, increased bore to 68 mm and shortened stroke to 51.5 mm, and switched from a crossplane to a flat-plane crankshaft. This Mk.III version produced 195 bhp at 9,500 rpm and powered Jim Clark and Lotus to seven victories, seven pole positions, six fastest laps, and the 1963 World Championship. A further evolved Mk.4 with 72.4 mm bore and 45.5 mm stroke produced 200 bhp at 9,750 rpm. Overall, the FWMV powered Cooper, Lotus, and Brabham to 22 World Championship Grand Prix victories.
The engine was technically notable for proving that flat-plane crankshaft design offered advantages over crossplane for racing V8 applications, a conclusion that became standard engineering practice from the 1970s onward.
Coventry Climax chairman Leonard Pelham Lee announced at Earls Court in 1962 that the company would withdraw from Formula One engine supply, citing costs and insufficient publicity benefit. The company attempted to develop a 1.5-litre flat-16 designated the FWMW for the final seasons of the small-capacity formula, but the project failed due to insurmountable crankshaft torsional vibration problems. The FWMW never raced, and when the three-litre formula arrived in 1966, Coventry Climax had no successor ready. A 2-litre version of the FWMV was assembled as a stopgap for Lotus in 1966, with Jim Clark winning the 1967 Tasman Series with it, but the company had already effectively exited racing.
Coventry Climax was purchased by Jaguar Cars in 1963. Its engineering team, led by Walter Hassan and Harry Mundy, subsequently developed the Jaguar V12 engine used in the E-Type and XJ12, a direct lineage from the racing work. The Dewar Trophy was awarded to Coventry Climax in 1964 by the Royal Automobile Club for its contribution to British Grand Prix racing achievement.
In the period 1958 to 1965 Climax-powered cars won 40 world championship Grands Prix, were runners-up on eight more occasions, and won 59 non-championship races. This record of achievement, built on engines that originated as fire pump units, represents one of the most remarkable engineering trajectories in motorsport history. The last championship win for a Climax-powered car in a world championship race occurred at the 1965 United States Grand Prix with Jim Clark driving a Lotus 33.