History
Among the early pioneers of DOHC were Isotta Fraschini's Giustino Cattaneo, Austro-Daimler's Ferdinand Porsche, Stephen Tomczak (in the Prinz Heinrich), and W. O. Bentley (in 1919); Sunbeam built small numbers of racing models between 1921 and 1923 and introduced one of the world's first production twin cams in 1924 — the Sunbeam 3 litre Super Sports, an example of which came second at Le Mans in 1925. The first DOHC engines were either two- or four-valve per cylinder racing car designs from companies like Fiat (1912), Peugeot Grand Prix (1912, four-valve), Alfa Romeo Grand Prix (1914, four-valve) and 6C (1928), Maserati Tipo 26 (1926), Bugatti Type 51 (1931).
When DOHC technology was introduced in mainstream vehicles, it was common for it to be heavily advertised. While used at first in limited production and sports cars such as the 1925 Sunbeam 3 litre, Alfa Romeo is one of the twin cam's greatest proponents. 6C Sport, the first Alfa Romeo road car using a DOHC engine, was introduced in 1928. Ever since this, DOHC has been a trademark of most Alfa Romeo engines (some Alfa V6 engines are SOHC, not DOHC. Most Alfasud boxer engines were also SOHC).
Fiat was one of the first car companies to use belt-driven DOHC engines in some of their products in the mid-1960s., Jaguar's XK6 DOHC engine was displayed in the Jaguar XK120 at the London Motor Show in 1948, and used across the entire Jaguar range through the late 1940s, 1950 and 1960s. By the late 1970s, Toyota was the best seller of DOHC engines.
More than two overhead camshafts are not known to have been tried in a production engine. However, MotoCzysz has designed a motorcycle engine with a triple overhead camshaft configuration, with the intake ports descending through the cylinder head to two central intake ports between two outside exhaust camshafts actuating one of two exhaust valves per cylinder each.
In inline piston aero engines, DOHCs have been used for many engines. The 1917 Napier Lion, for example, had them.
Read more about this topic: Overhead Camshaft
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