Hi All,  I am curious about the pieces of felt (three total, one for
each valve) used as the upper valve seats for the lock valves (part
no. 29 in the 1923 Inspector's Reference Book, page 9) in the Ampico
expression mechanism.

I have heard of people replacing these with a leather seat with
the understanding that it improves the overall performance of the
expression mechanism by reducing the leakage between the upper portion
of this valve and its seat.

However, I doubt that Ampico installed felt here by mistake.  This
leads me to believe a bit of leakage may be desirable (or necessary).
Does anyone have any thoughts on this subject?

Many thanks,
Rob Buckingham
Pittsburgh, Pennsylvania