 This led to significant energy losses in the engine, but was simpler, especially in a V engine where one camshaft can actuate the valves for both cylinder banks; for this reason, pushrod engine designs have persisted longer in these configurations than others.More modern designs have the camshaft on top of the cylinder head, pushing directly on the valve stem (again through cam followers, also known as tappets), a system known as "overhead camshaft"; if there is just one camshaft, this is a single overhead cam or "SOHC" engine.Often there are two camshafts, one for the intake and one for exhaust valves, creating the dual overhead cam, or "DOHC".