- When the cam lobe comes up under the valve lifter, the lobe will push the lifter up. This pushes the pushrod up.
- Pushrod movement causes the rocker arm to rock on its pivot. As one end of the rocker arm moves up, the other end moves down.
- The valve spring is compressed as the rocker arm pushes the valve stem down. This forces the valve off its seat to open valve.
- When the cam lobe passes out from under the valve lifter, the valve spring expands. The spring forces the valve back up onto its seat. The spring forces the valve back up onto its seat. The stem end of the rocker arm goes up. As the other end goes down, it pushes the pushrod and valve lifter back down,