While pricing a new cam - the DC engine book says I need these springs.
if the valve is wide open and passes all the air the port can flow then
will opening the valve further accomplish anything?
I will tell you that you can't predict exactly what the port does under load. Like I said, I take a pretty damn good head and make it back up on the bench. All heads do it.
I'll take more time with the valve out of the way then to have the valve not open as far. You can use lift averaging.
As I've posted before, I'm not a low lift flow guy. The piston is in the way, and there is no need to have both valves off the seat, flowing like a banshee. Then you have to reduce overlap at the cam.
There is more to it than just saying don't open the valve any further than where flow stalls. I'd should say more but it costs big money to learn this stuff. I don't mind helping, but some of it I just don't want to disclose.
I will say this....flowing at 28 inches is pretty much a waste of time, except for comparison. To develop a port, there is more to it than 28 inches.