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There are three main parameters that determine the nature of that open-and-shut dance: timing, lift and duration.

As those cam lobes rotate, the high part of their egg shape presses on the valve, moving it into an open position.Ĭamshafts come in many sizes and applications, but all have a series of eccentric, or egg-shaped, cams machined into them.Īs that cam lobe continues to rotate, its high part moves away from the valve and a spring returns the valve to its shut position. How valves workĮngine valves are operated by the rotation of a camshaft that has eccentric, egg-shaped lobes on it. That may sound like a couple of horns in an orchestra, but valves are actually central to the nature of an engine's power, economy and emissions. Highlighted are the valves of an engine, positioned in the head (invisible here), directly above the cylinders. The valves are installed in a part of the engine called the head and are responsible for letting air and/or fuel into the cylinders to be combusted - those are called intake valves - and for letting the exhaust from that combustion out of the cylinders - those are called exhaust valves.