A cylinder head sliced in half shows two overhead camshafts—one above each of the two valves.

A double overhead cam (also called a dual overhead cam, DOHC, or "twincam") engine is a type of internal combustion engine where the camshafts that operate the intake and exhaust valves are mounted above the cylinders, and where there are separate camshafts for inlet and exhaust valves. In engines with more than one cylinder bank, such as the V engine, this designation means two camshafts per bank......... Image File history File links Source copied from de:Bild:DOHC-Zylinderkopf-Schnitt. ... Image File history File links Source copied from de:Bild:DOHC-Zylinderkopf-Schnitt. ... The cylinder head from a GMC van. ... poppet valve A poppet valve is the type of valve system used in most piston engines, used to seal the intake and exhaust ports. ... It has been suggested that Car engine be merged into this article or section. ... The camshaft is an apparatus used in piston engines to operate poppet valves. ... poppet valve A poppet valve is the type of valve system used in most piston engines, used to seal the intake and exhaust ports. ... A piston and cylinder from a steam engine A cylinder in an internal combustion engine is the space within which a piston travels. ... Piston engines are typically arranged with their pistons in rows, moving inside individual cylinders. ... A V engine is a common configuration for an internal combustion engine in which the pistons are aligned so that, if viewed along the line of the crankshaft, they appear to be in a V. Usually, two opposing pistons share one crank on the crankshaft. ...

Usually the cams operate the valves directly or by a short rocker, as opposed to pushrod engines which have long rods to transfer the movement of the lobes on the camshaft in the engine block to the valves in the cylinder head. The cylinder head from a GMC van. ...

Double camshafts are not required in order to have multiple inlet or exhaust valves, but are necessary for more than 2 valves that are directly actuated (though still usually via tappets). However, not all DOHC engines are multivalve engines - DOHC was common in 2-valve engines for decades before multivalve heads appeared. Today, DOHC is normally synonymous with multivalve, since almost all DOHC engines also have between 3 and 5 valves per cylinder. In automotive engineering, an engine is referred to as multi-valve (or multivalve) when it has more than two valves. ... In automotive engineering, an engine is referred to as multi-valve (or multivalve) when it has more than two valves. ...

History

DOHC straight-8 in a 1933 Bugatti Type 59 Grand Prix racer

The first DOHC engines were 2-valve designs from companies like Fiat (1912), Peugeot (1913), Alfa Romeo (6C- 1925, 512 - 1940), Maserati (Tipo 26, 1926), and Bugatti (Type 51, 1931). Most Ferraris used 2-valve DOHC engines as well. Image File history File links Download high resolution version (2185x1295, 343 KB) 1933 Bugatti Type 59 Grand Prix From the Ralph Lauren collection on display at the Boston Museum of Fine Arts. ... Image File history File links Download high resolution version (2185x1295, 343 KB) 1933 Bugatti Type 59 Grand Prix From the Ralph Lauren collection on display at the Boston Museum of Fine Arts. ... A double overhead cam (also called a dual overhead cam, DOHC, or twincam) engine is a type of internal combustion engine where the camshafts that operate the intake and exhaust valves are mounted above the cylinders, and where there are separate camshafts for inlet and exhaust valves. ... 1933 Bugatti DOHC straight-8 in a Type 59 Grand Prix racer 1940s Oldsmobile Straight-8 engine A Straight-8 is a straight engine with eight cylinders. ... 1933 Bugatti Type 59 Grand Prix racer from the Ralph Lauren collection Wikimedia Commons has more media related to: Category:1933 Bugatti Type 59 Grand Prix The Type 51 series succeeded the famous Type 35 as Bugattis premier racing car for the 1930s. ... Georges Boillot winning the 1912 French Grand Prix in Dieppe, France Grand Prix motor racing has its roots in organized automobile racing that began in France as far back as 1894. ... Fiat S.p. ... Peugeot is a major French car brand which is today part of PSA Peugeot Citroën. ... Alfa Romeo is an Italian automobile manufacturing company, founded as Darracq Italiana by Cavaliere Ugo Stella, an aristocrat from Milan in partnership with the French automobile firm of Alexandre Darracq. ... Present Maserati logo (see also original logo) Maserati is a famous Italian manufacturer of racing cars and sports cars, established in 1914 in Bologna. ... Bugatti is one of the most celebrated marques of automobile and the one of the most exclusive Italian car producers of all time. ... 1933 Bugatti Type 59 Grand Prix racer from the Ralph Lauren collection Wikimedia Commons has more media related to: Category:1933 Bugatti Type 59 Grand Prix The Type 51 series succeeded the famous Type 35 as Bugattis premier racing car for the 1930s. ... The Ferrari Gestione Industriale badge on the front of a 330 GTC Ferrari is an Italian manufacturer of high end race cars and high-performance sports cars formed by Enzo Ferrari in 1929. ...

When DOHC technology was introduced in mainstream vehicles, it was common for the technology to be heavily advertised. Fiat, Lancia and Alfa Romeo can be credited with placing mass produced twin cam (DOHC) engines in coupés, sedans, convertibles, and station wagons beginning in the mid 1960s. Later, in the mid-1980s Honda products featured "DOHC" plaques, and automakers often used "DOHC" as the engine's name. Most early mainstream DOHCs were 4-cylinder engines as well: Ford's first DOHC motor was the Lotus-reworked Kent (1962), and General Motors' first was the 1975 Cosworth-tweaked 2300, though by comparison, Toyota debuted two production DOHC engines in 1967: the inline-4 9R engine (Corona 1600GT) and the Yamaha-designed straight-6 3M engine (2000GT). 1995 Buick Riviera coupé A coupé (from the French for cut) or coupe is a car body style with a close-coupled interior offering either two seats or 2+2 seating (space for two passengers up front and for two occasional passengers in the rear). ... A Ford Taurus, a recognizable sedan. ... Saab 900 Convertible Convertible can also refer to a convertible (security) A convertible is an automobile with a folding or retracting roof. ... Estate car body style (Saab 95) A station wagon (United States usage), wagon (Australian usage, though station wagon is widely used) or estate car (United Kingdom usage) is a car body style similar to a sedan car but with an extended rear cargo area. ... The 1960s decade refers to the years from 1960 to 1969, inclusive. ... The 1980s decade refers to the years from 1980 to 1989, inclusive. ... Honda Motor Co. ... Ford may mean a number of things: A ford is a river crossing. ... Lotus Cars is a British manufacturer of sports cars and racing cars based in East Anglia, and formed as Lotus Engineering Ltd. ... The Ford Kent is an internal combustion engine from Ford of Europe. ... You may be looking for the arena found in Vancouver, see GM place General Motors Corporation NYSE: GM, also known as GM, is a United States-based automobile maker with worldwide operations and brands including Buick, Cadillac, Chevrolet, GMC, Holden, Hummer, Opel, Pontiac, Saturn, Saab and Vauxhall. ... A Ford Cosworth DFV on a Ligier JS11 Cosworth is an engine design and manufacture company founded in 1958, specialising in engines for automobile racing. ... The 2300 was a 2. ... Toyota redirects here. ... 1967 (MCMLXVII) was a common year starting on Sunday of the Gregorian calendar. ... Usually found in 4 and 6 cylinder configurations, the straight engine (often designed as inline engine) is an internal-combustion engine with all cylinders aligned in one row, with no or only minimal offset. ... Toyota Motor Corporation has produced a wide variety of automobile engines. ... 1960 Toyota Corona, the second generation of the car, with American-influenced styling. ... Yamaha Motor Corporation (ヤマハ発動機株式会社) is a motorized vehicle-producing company, initially part of the Yamaha Corporation. ... The straight-6 (also inline 6, I-6, or I6) is an internal combustion engine with six cylinders aligned in a single row. ... Toyota Motor Corporations M family of engines were a longitudinally mounted straight-6 engine design. ... Toyota 2000GT. Note the slippery lines, reminiscent of the Jaguar E-Type. ...

See also

• Overhead camshaft
• Single overhead cam
• Pushrod

Single overhead cam (also SOHC) refers to the internal combustion engine design where one camshaft is located above the valves. ... A pushrod engine or overhead valve (OHV) engine is a type of piston engine that places the camshaft below the pistons (usually beside and slightly above the crankshaft in a straight engine or directly above the crankshaft in the V of a V engine) and uses pushrods or rods to...

External links

• OHV, SOHC, DOHC engine animated diagrams