Which statement best describes the role of the camshaft?

• A. Converts linear motion to rotary motion
• B. Converts rotary motion to reciprocating motion
• C. Provides lubrication to engine
• D. Delivers fuel to cylinders

Answer: (B)

The camshaft’s job is to turn the crankshaft’s rotary motion into the up-and-down, or reciprocating, motion needed to open and close the engine’s valves. Its lobes push valve lifters (or rocker arms) so each valve lifts against its spring, allowing the air-fuel mixture in and exhaust gases out at the right times in the cycle. In a typical four-stroke engine, the camshaft usually rotates at half the crankshaft speed, coordinating every valve event with the piston’s position. Lubrication and fuel delivery come from other systems, so this description most accurately captures the camshaft’s function.