AG Mechanics CDE Practice Exam

What pushes against the valve tappets to make them move?

1. Cam lobes

2. Pushrods

3. Valve guides

4. Valve springs

The correct answer is: Cam lobes

Cam lobes push against the valve tappets to make them move in an internal combustion engine. The camshaft has lobes that are specifically designed to push against the valve tappets, which in turn open and close the valves at the appropriate times during the engine's operation. Pushrods transfer the motion from the cam lobes to the valve tappets, valve guides provide guidance for the valve stem, and valve springs help to close the valves after they are opened. However, the primary component responsible for pushing against the valve tappets to make them move is the cam lobes.