Single overhead cam is a term which refers to a single camshaft located above the [cylinderhead] of each bank of cylinder composing an engine. The single camshaft actuates both the intake valves and the exhaust valves.

The majority of SOHC engines also have only 2 valves per cylinder, such as the Nissan Z-series or L-series; however some cylinder heads are designed so that a single cam can actuate multiple intake and/exhaust valves, such as the 12 valve nissan KA24 which uses a single cam to actuate two intake and one exhaust valve per cylinder.

see also: Dual overhead cam