Ideally, you want the incoming air/fuel to center in the port and hit the back of the valve head dead center so that it spreads around the valve a complete 360*. I keep coming back to the point that the shortest distance between two points is a straight line, and above a certain speed in the port if the port shape is not conducive to keeping the airflow centered, the air will shear and take the shortest path over the valve face. That is the reason for the "pop" and reduction of flow in ports. Most of the air then flows over the short side, and the top of the port is dead. The only way to alleviate that issue is to kick the airflow back up into the top of the port so that it goes over the front of the valve into the chamber. As the valve opens further, the flow over the short side will begin to fluctuate and go over parts of the valve that is unshrouded. A combustion chamber that has a wall close to one side of the valve will kick the airflow in the opposite direction, and airflow will decrease or stagnate. The more you take the short turn down, the more you create a waterfall affect and the air will take that shortest distance, especially with a very short turn like the FE or SBF. The higher the short turn, the easier it is to kick the airflow up into the port and have it flow over the complete valve face. Velocity helps with keeping the airflow slamming into the front of the port and going over the front of the valve head and not shearing over the short turn. Joe-JDC