Zenith Zenith The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere. "Above" means in the vertical direction opposite to the apparent gravitational force at that location. The opposite direction, i.e. the direction in which gravity pulls, is toward the nadir. The zenith is the "highest" point on the celestial sphere. The word "zenith" derives from an inaccurate reading of the Arabic expression (), meaning "direction of the head" or "path above the head", by Medieval Latin scribes in the Middle Ages (during the 14th century), possibly through Old Spanish. It was reduced to 'samt'
Overhead camshaft more than one cylinder head, such as a V engine or a horizontally-opposed engine (boxer; flat engine) – there are two camshafts, one per cylinder bank. In the SOHC design, the camshaft operates the valves directly, traditionally via a bucket tappet; or via an intermediary rocker arm. SOHC cylinder heads are generally less expensive to manufacture than double overhead camshaft (DOHC) cylinder heads. Timing belt replacement can be easier since there are fewer camshaft drive sprockets that need to be aligned during the replacement procedure. SOHC designs offer reduced complexity compared with overhead valve designs when used for multivalve cylinder