The cam-in-block valvetrain layout of piston engines is one where the camshaft is placed within the cylinder block, usually beside and slightly above the crankshaft in a straight engine or directly above the crankshaft in the V of a V engine. This contrasts with an overhead camshaft (OHC) design which places the camshafts within the cylinder head and drives the valves directly or through short rocker arms. There are three main cam-in-block designs: * L-head, also known as L-block, flathead or sidevalve * F-head * I-head, also known as overhead valve (OHV)