The Hispano-Suiza H6 is a luxury car that was produced by Hispano-Suiza, mostly in France. Introduced at the 1919 Paris Motor Show, the H6 was produced until 1933. Roughly 2,350 H6, H6B, and H6C cars were produced in total. Specifications The H6 engine featured a straight-six engine inspired by designer Marc Birkigt's work on aircraft engines. It was an all-aluminium engine displacing . Apart from the new overhead camshaft, it was essentially half of Birkigt's aviation V12 design. The seven-bearing crankshaft was milled from a steel billet to become a sturdy unit, while the block used screwed-in steel liners, and the water passages were enamelled to prevent corrosion. One of the most notable features of the H6 was its brakes. They were light-alloy drums on all four wheels with power-assist the first in the industry, driven with a special shaft from the transmission. When the car was decelerating, its own momentum drove the brake servo to provide additional power. This technology was later licensed to other manufacturers, including arch-rival Rolls-Royce. The 1922 H6B was slightly more powerful. An () engine was used in 1924's H6C. The H6 series was replaced in 1933 by the J12, which initially used a V12 pushrod engine. Special versions A series of five racing H6Bs with short wheelbases and slightly enlarged engines was built in 1922. These were referred to as "Boulogne", to celebrate the H6's triple victory at the sports car race at Boulogne by pilots Dubonnet, Garnier, and Boyriven in 1923 (Journal des debats, July 27, 1923). Woolf Barnato piloted a Boulogne to eight international records, including a average over , at Brooklands in 1924. André Dubonnet entered an H6C Boulogne in the 1924 Targa Florio. Powered by a straight 6 (estimated to produce ), Dubonnet demanded a maximum body weight of , and the aircraft maker Nieuport- Astra complied with tulipwood strips (later determined to have been mahogany), fastened to an aluminium frame with thousands of tiny rivets. Dubonnet finished the gruelling event without a body failure, and drove home to Naples afterward. This vehicle is currently housed at the Blackhawk Museum near Danville, California. A later series of short-wheelbase H6Cs was built, eventually being referred to as "Monzas". A six-wheeled H6A was ordered by the King of Greece, but after his abdication was purchased by the motion picture director D. W. Griffith. It is now at the Forney Museum in Denver.