What are tappets primarily associated with in an engine?

Tappets are primarily associated with valve operation in an engine. They are components that transfer the motion from the camshaft to the engine's valves, enabling the opening and closing of the valves at the correct timing during the engine's cycle. This is crucial for engine performance, as the precise operation of the valves allows for effective intake of air and fuel and efficient exhaust of combustion gases. The correct functioning of tappets ensures that the valves operate smoothly and efficiently, which is essential for maintaining the engine's overall performance and efficiency.

In contrast, other options, such as fuel delivery, exhaust removal, and air filtration, pertain to different systems within the engine. Fuel delivery involves mechanisms like fuel pumps and injectors that supply the engine with the necessary fuel. Exhaust removal is handled by components like the exhaust valves and the exhaust system that expels combustion gases. Air filtration involves the air cleaner that filters air entering the combustion chamber, ensuring that dirt and debris are removed. Each of these systems plays an important role, but tappets specifically relate to the critical function of managing valve movement.