Airflow to Cubic Inches

The cam also affects the port velocity. Lets say you're sucking on a straw. Not sure how to word this without sounding dirty. Your mouth would be the piston and the straw the port. Changes in how hard you suck on the straw can be compared to rpm changes. Now your finger tip will be the valve which is controlled by the cam. The faster you move your finger off the straw and the further you move it away from the straw affects the air speed through the straw.