What is Camshaft?
The shaft with lobes that operate intake and exhaust valves. Camshaft profile (lift, duration, timing) determines engine power characteristics.
Camshaft (often shortened to cam) is the rotating shaft inside an engine with lobes (cams) that open and close the intake and exhaust valves at precise timings. Camshaft profile (the shape, height, and timing of the lobes) is one of the most influential factors in engine power characteristics. Different cams produce dramatically different power curves on the same engine block.
Three main cam parameters define the profile. Lift describes how far the valve opens (higher lift = more airflow but more stress on valvetrain). Duration describes how long the valve stays open (longer duration = more peak power but typically worse low-RPM behavior). Timing describes when in the engine cycle the valve opens and closes relative to piston position. Aftermarket cams typically increase one or all of these to shift the power band higher in the RPM range.
Modern engines use multiple camshafts. Single overhead cam (SOHC) engines have one cam per cylinder bank. Double overhead cam (DOHC) engines have two cams per bank (one for intake, one for exhaust). Variable valve timing (VVT, like Honda VTEC, BMW VANOS, Toyota VVT-i) varies the cam timing electronically based on engine RPM and load, providing different cam profiles for different operating conditions.
