Nadir Nadir The nadir (, ; from / ALA-LC: "naẓīr", meaning "counterpart") is the direction pointing directly "below" a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface there. Since the concept of "being below" is itself somewhat vague, scientists define the nadir in more rigorous terms. Specifically, in astronomy, geophysics and related sciences (e.g., meteorology), the nadir at a given point is the local vertical direction pointing in the direction of the force of gravity at that location. The direction opposite the nadir is the zenith. Nadir is
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