Each H.D. head has port shifting going on due to core shifts during assembly or casting.
Port walls are to the right or the left, port floors high or low.
Understanding flow movement inside the ports and directing the flow in an orderly manner increases CFM and velocity. The goal is to do this in the smallest port possible. Producing above average head work for the street requires a great deal of knowledge. The flow bench is indispensable in the testing of port shapes. For a more indepth discussion on porting click here .