Andy Taylor and others were right and confirmed what I had observed
about the inside valve facings.  Andy wrote:

> Consider this for a moment: When the note is "on" the pouch is trying
> to push the valve toward the outer seat.  The suction in the valve
> chest at the same time is also drawing the valve in the opposite
> direction that the pouch is trying to push it.  Even when the pouch
> overcomes the balance, and pushes the stem forward, your valve is
> flexing and 'hugging' the seat, compensating for what valve travel you
> have set.

This is the case and I have purchased the proper valve facings and will
be re-working the valves.  I have not chosen to change the original
design by gluing the leather to a fiber disk and eliminating the metal
backing plates.  Since I have to take the valves apart again I will
simply re-leather using the proper materials.

A special thanks to all who have responded to me.  This is such a great
way to communicate.

"Every man knows something I do not; therefore, every man is my
teacher."

Sam Harris - Greenville, NC
http://www.geocities.com/Heartland/Ranch/9374
http://www.geocities.com/Heartland/Ranch/9374/autoinde.html