Dual Overhead Camshafts is an engine with two camshafts that are usually located in the cylinder head.
Many inline overhead camshaft engines use one camshaft. These are single overhead camshaft (SOHC) engines. Other inline engines use two overhead camshafts wherein one camshaft operates the intake valves The other camshaft operates the exhaust valves. V-type engines may have one or two camshafts in each cylinder head.Sometimes a DOHC V engine is called a quad-cam engine however, there are extra two camshafts which are the results of an engine layout rather than providing a benefit compared with the DOHC engine. The camshaft usually operates the valve directly through a bucket tappet. A DOHC type has the ability to allow a wide-angle between intake and exhaust valves compared to a SOHC (Single Overhead Cam) that enables to improve air-fuel mixture flow through the engine