Section Contents:- A double overhead camshaft (also called DOHC, dual overhead cam, or twin cam (TC) ) valve train layout is characterized by two camshafts being located within the cylinder head, where there are separate camshafts for inlet and exhaust valves.(More...)
- The Ford I4 DOHC engine was a 4-cylinder inline internal combustion engine with twin overhead camshafts, produced by the Ford Motor Company.(More...)
A double overhead camshaft (also called DOHC, dual overhead cam, or twin cam (TC) ) valve train layout is characterized by two camshafts being located within the cylinder head, where there are separate camshafts for inlet and exhaust valves. [1] The term Twin Cam doesn't tell the exact location of camshafts, but it is mostly used to describe DOHC structure.
[1] 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 between 1921 and 1923.
[1] Not all DOHC engines are multivalve engines"DOHC was common in two valve per cylinder heads for decades before multivalve heads appeared, however today DOHC is synonymous with multi-valve heads, since almost all DOHC engines have between three and five valves per cylinder.
[1] The first DOHC engines were two- or four-valve per cylinder designs from companies like Fiat (1912), Peugeot Grand Prix (1913, 4 valve), Alfa Romeo GP (1914, 4 valve) and 6C (1925), Maserati Tipo 26 (1926), Bugatti Type 51 (1931), and Audi.
[1] 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, FIAT is credited as the first car company to use a belt-driven DOHC engine across their complete product line, in the mid-1960s.
[1] 
The Ford I4 DOHC engine was a 4-cylinder inline internal combustion engine with twin overhead camshafts, produced by the Ford Motor Company. [2] DOHC or Double OverHead Cam - the setup used in many today's cars. Since it's possible to install multiple valves per cylinder and place intake valves on the opposite side from exhaust vales, DOHC engine can "breath" better meaning that it can produce more horsepowers with smaller engine volume.
[3] You can actuate four valves per cylinder (or three, like Mercedes-Benz) with one camshaft by using rocker arms to open one set or both, depends on how you want to do it. As for DOHC, again, there is an advantage in weight, at an extra cost, both financially and in complexity. It costs more to grind two camshafts than one and it takes more stuff to drive two cams than one. Otherwise, it's much like SOHC.
[4] Remember, Roger Penske's car won the Indy 500 a few years ago with a pushrod engine, everybody else had DOHC.
[4] 
