OHV – OverHead Valve
an engine design where the camshaft is installed inside the engine block and valves are operated through lifters, pushrods and rocker arms
Advantages of an OHV: lower cost, compact size and proven durability.
SOHC -Single OverHead Cam
In a SOHC engine the camshaft is installed in the cylinder head and valves are operated either by the rocker arms or directly through the lifters.
Advantages of sSOHC– precise timing at higher RPMs, possible to install three or four valves per cylinder.
DOHC-Double OverHead Cam
DOHC engine has two camshafts and 4 valves per cylinder. One camshaft operates intake valves while another camshaft controls exhaust valves.
Advantages oh DOHC-DOHC engine can “breathe” better and thus produces more horsepower out of smaller engine volume.