I wish to buy a set of rebuildable secondary Ampico unit stack valves.
The late A valves I have are marginal and the burnt shellac sealing
is so heavy that normal methods of rebuilding are not working.

These valves had special properties -- a factory-original top seat
restriction consisting of a leatherette circle with 1/8-inch hole
placed on top of the top seat.  The burnt shellac almost covers the
fluted metal top seat.  Even after melting the shellac, the top seat
gets bent while removing it.  The entire valve unit appears to be
coated with very heavy shellac.

So its a matter of obtaining restorable set of valves for the late
A Ampico.  I will also be seeking leather suitable for valve facings.
For the record, these valves are shown (on the right) in Paul
Manganaro's very helpful information at
http://antiquemechanicalrestorations.com/4_Unit_Valves.html 

Bill Chapman -- in windy, hot, La Quinta, Calif.