In answer to Rob's valve seating problem:  This is a mistake I and
others have made in replacing the leather valve facings in Autopiano
and similar type valves that use force-fit collars to hold the facing
in place.  The valve seats and guides are not always perfectly aligned
so the facing and the plate behind it must be free to pivot a bit so
the valve can seat properly.  If the force-fit washers are too tight,
the valves will absolutely not seat.

You can easily refer to an original valve to see the amount of pivot is
needed.  Some valves have an additional piece of leather or very thin
felt to insure this.  Make sure the center hole in the leather facing
tight fit on the stem so it can pivot but not leak.

Brian Thornton