Double camshaft at the head

The double camshaft at the head (DOHC = Double overhead camshaft in English) is one alternative of the Camshaft at the head, where the lines of Valve S of admission and exhaust each one are actuated by a tree.

This technique makes it possible to almost remove all the adapters between the Camshaft and the valve, without needing, for as much, to align all the valves. The engine can, thus, turn more quickly and produces less mechanical noises.

The concept of double tree is conceived only for each line of Cylindre S. For example, a V-engine which would not have that a camshaft by line of cylinders is regarded as simple tree, although it has two camshafts in all.

Sometimes, certain engines with several lines of cylinders are known as QOHC or quadruple camshaft at the head. That indicates in fact an engine where each line of cylinder at the head has a double camshaft. Thus, the terms V6 DOHC or V6 QOHC indicate the same thing strictly.

The double camshaft is often associated with the distributions using 4 valves per cylinder, but it is not an obligation.

One finds traces of double tree since 1912, at FIAT.

The double camshaft at the head started to spread in the Années 1960 in car.

In motor bike, generalization on the vehicles of tourism was the fact of the Japanese constructors.

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