The _____ opens and closes valves.

• A. Piston
• B. Camshaft
• C. Crankshaft
• D. Timing Belt

Answer: (B)

Camshaft is what opens and closes the valves. Its cam lobes push on valve lifters or rocker arms to lift the intake and exhaust valves at the correct moments in each engine cycle. When the cam lobe rotates away, the valve spring returns the valve to the closed position. The piston moves up and down in the cylinder to compress air-fuel and transfer force to the crankshaft, but it doesn’t control valve timing. The crankshaft drives the pistons and provides rotational motion, not valve actuation. The timing belt or chain simply keeps the camshaft and crankshaft in sync so valve timing remains correct; it doesn’t itself open or close the valves.