Which component opens and closes the valves?

• A. Pushrod
• B. Camshaft
• C. Lifter
• D. Timing Chain

Answer: (B)

The camshaft is responsible for opening and closing the valves. Its lobes push against lifters (or followers), which transmit that motion through pushrods to the rocker arms (in a pushrod engine) or act directly on the valve in an overhead-cam design. As a lobe pushes the follower up, the valve is opened against the spring; when the lobe moves away, the spring forces the valve closed. The timing chain’s job is to keep the camshaft turning in sync with the crankshaft, not to open or close the valves itself. The lifter and pushrod merely transfer motion from the cam lobe to the valve system.