What is the function of the camshaft in an internal combustion engine?

• A. Opening and closing the inlet and exhaust valves
• B. Firing the spark plugs
• C. Controlling fuel metering
• D. Rotating the crankshaft

Answer: (A)

The camshaft’s job is to operate the engine’s valves. Its lobes push on valve lifters or rocker arms as it rotates, causing the intake and exhaust valves to open and then close at the correct moments in the piston’s cycle. This timing lets the air-fuel mixture enter and exhaust gases exit when the piston is in the right positions, and it ensures the combustion chamber seals during compression and power strokes. In a four-stroke engine, the camshaft typically turns at half the crankshaft speed, keeping valve timing in sync with piston movement. Other systems don’t perform this timing role: ignition systems fire the spark plugs, fuel metering systems control fuel flow, and the crankshaft provides the primary rotational motion that drives the pistons.