What device consists of a cylindrical rod running the length of the engine block with several oblong lobes that operate various valves?

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

Answer: (C)

The device described is the camshaft. It is a long cylindrical rod that runs the length of the engine block in many OHV designs. Along the shaft are cam lobes that are shaped to push against lifters and pushrods (or rocker arms) as the shaft rotates. Each cam lobe, as it turns, opens its corresponding valve for a precise moment in the engine cycle, letting air and fuel in or exhaust out. The camshaft is timed to rotate in sync with the crankshaft, typically driven by a timing belt, chain, or gears, to ensure valves open and close at the correct times relative to piston position. The piston and connecting rod move up and down inside the cylinder and feed motion into the crankshaft, not into valve operation. The crankshaft itself is a rotating shaft with throws that converts piston motion into rotational energy, and it does not use lobes to operate valves.