Double overhead cam

Double overhead cam

A double overhead cam (or DOHC) engine is a type of internal combustion engine where the camshafts that operate the valves are mounted above the cylinders, operating the valves directly, and where there are seperate camshafts for inlet and exhaust valves. Double camshafts are required in order to have multiple inlet or exhaust valves that are directly actuated.

Most recent internal combustion engine designs are of the DOHC type, since it allows for greater efficiency. In engines with more than one cylinder bank, such as the V engine, this designation means two camshafts per bank.

When the DOHC concept was introduced, it was common for the first such engine from a manufacturer to be known as the DOHC engine; for instance, Ford's new DOHC straight-4 in the late 1980s.