Why is rocker geometry important?

The main thing we are looking for in geometry is the pattern on the valve stem to ensure that valve guide wear is at a minimum.

The roller tip needs to start towards the intake port side of the head when the valve is closed. The rocker should then roll out to just past center towards the exhaust side of the head at half lift. Then from half lift to full lift, it should roll back to where it originated on the intake port side of the valve stem. The amount of tip travel will be directly affected by how much lift there is at the valve.

Example: If you have 0.550” lift, the roller tip should start 0.020-0.025” before centerline of the valve stem. If you had 0.650” lift, this pattern will roll back towards the intake side of the head and be 0.025-0.030”.