Engine block: Camshafts
Via roller bearings, the camshafts act on rocker arms that are supported in ball cups at one end, constituting the upper end of the hydraulic valve clearance balancers, and press against the valve stems at the other end. The hydraulic valve clearance balancers maintain the clearance between the camshaft and the rocker arm/roller bearing close to zero. Consequently, they do not take part in any movement. This design requires a low level of friction for its movement. See also CAMSHAFT DRIVE .