affect of valve stem on air flow

Is there a way to figure out what affect the diameter of a valve stem would have on air flow?
Currently have 3/8 valves and thinking of going to a 5/16 stem.

I can tell you that changing from "waisted" 3/8" to "waisted" 11/32" was good for 1-2 cfm (max) on a set of my old heads that were converted to narrower valve stems.

valve itself should be lighter

Quote:

---

valve itself should be lighter

---

Ya, I think the big gain is weight reduction for a more stable valve train operation at high rpm"s.