Another thing to consider is that there will be pressure differences at every lift of the valve.A pressure of 40" might exist at .400 lift and then drop to 30" at .500 lift all in the same stroke.That would mean that the terminal velocity of a port at some lift in the same stroke would precede what the terminal velocity would be at some other lift.So in actuality even if a head were to flow some maximum flow on the bench at so and so lift it may never see that potential in real engine performance.Ejit touched on the idea that rod ratio may be something to consider in designing a cam. I believe that to be totally something to consider.This has been brought up before and is something i'm incorporating into the design of my next flow bench.When we see flow charts for ports we usually see every lift of the valve flowed at the same test pressure(28"....25"....etc.)But the same pressure for each lift in a real engine doesn't see the same pressure at the same engine speed.The pressure varies with each lift.Possibly a properly designed cam lifting just the right amount to avoid that terminal velocity at every lift until much later might be the way to go.I believe one way to determine that would be to have a flow curve not based on flow at every lift at some same depression but a flow curve that shows the flow at every lift within the same rpm range in actual conditions.I've thought about this somewhat and how to measure this.I've got a good idea on how this can be done.