Another important note is that the Rocker Ratio is always changing because the Rocker Arm tip is moving on an arc around it's center pivot point, but the valve stem goes straight up and down. This means that as the Rocker Arm moves, the distance from the pivot point to the contact point on the valve stem is always changing. If this distance is changing, the Rocker Ratio is also changing. Typically, the amount of change for a nominal 1.5 Rocker Ratio in a pushrod engine is from 1.45 to 1.55 as it goes through it's arc.
