Phil Dayson had a great idea of checking the flow through bleed cups.
Ampico did the same thing and discovered that turbulence alone could
change the effective size of a bleed quite a bit.

Actually, this is a characteristic of every thin orifice which has not
been centered, drilled and deburred perfectly.  Apparently though, it
isn't too important in the majority of cases.

However, if you want to learn how to size a bleed for any particular
valve and get them all idealized, the method is detailed in The
Orchestrion Builder's Manual Chapter 7, Valves and Cutouts, pg. 66.
It tells you what the principle is, why it works that way, and to what
degree this may be critical.  You will also find more information in the
Appendix H, pg. 206.

Craig Brougher