Single overhead camshaft
SOHC stands for single overhead cam and is a design in which one camshaft is placed within the cylinder head. In an inline engine this means there is one camshaft in the head, while in a V engine or a horizontally-opposed engine (boxer; flat engine) there are two camshafts: one per cylinder bank.
The SOHC design has less reciprocating mass than a comparable pushrod design. This allows for higher engine speeds, which in turn will increase power output for a given torque. The cam operates the valves directly or through a rocker arm, as opposed to overhead valve pushrod engines which have tappets, long pushrods, and rocker arms to transfer the movement of the lobes on the camshaft in the engine block to the valves in the cylinder head.
SOHC designs offer reduced complexity compared to pushrod designs when used for multi-valve heads in which each cylinder has more than two valves. Of all valvetrain systems, this is the least complex configuration possible.