Which component is least likely needed in an overhead cam engine design?

In an overhead cam (OHC) engine design, the camshaft is located directly above the cylinder head, which enables more efficient operation of the engine's valves. This design eliminates the necessity for pushrods, which are typically used in overhead valve (OHV) engines to transfer motion from a camshaft located in the engine block to the valves.

By incorporating the camshaft in the cylinder head, OHC engines can benefit from more precise timing and fewer moving parts, which enhances reliability and performance. The direct connection between the camshaft and the valves allows for shorter valve actuation pathways, resulting in less mechanical complexity and weight.

Pistons and crankshafts, on the other hand, are essential components in all engines, including OHC designs. Pistons are critical for creating the compression needed for combustion, while the crankshaft converts the linear motion of the pistons into rotational motion to power the vehicle. Therefore, while pushrods play a crucial role in OHV engines, they are not necessary in overhead cam designs, making them the least likely component to be needed.