camshaft

A camshaft is a shaft to which one or more cams are attached. The cams are eccentric lobes that convert rotary motion into the lifting motion of engine valves. In internal combustion engines, the camshaft operates the intake and exhaust valves via pushrods, rocker arms, or directly in compact designs. The timing between the crankshaft and the camshaft determines when the valves open and close during the engine cycle.

Camshaft profiles control lift, duration, and valve events. The shape of each lobe defines the valve lift (how far the valve opens) and the timing of opening and closing. Higher lift and longer duration generally increase airflow but can affect idle, emissions, and reliability. Tolerances and surface finish are critical and cam lobes are hardened to resist wear.

Drive and placement. Camshafts are driven by the crankshaft through a timing belt, timing chain, or gears. In pushrod engines the camshaft is located in the engine block with lifters and pushrods; in overhead cam engines it sits in the cylinder head, and may be called SOHC (single overhead cam) or DOHC (dual overhead cam) depending on the number of camshafts per bank. Camshafts are lubricated by engine oil and supported by bearings.

Modern engines may use variable valve timing (VVT) with adjustable cam timing, cam phasers, or electric actuation to improve efficiency and power across operating conditions. Cam profiles and configurations vary by engine and manufacturer, and camshafts are common targets for tuning and performance modification.