I have a Melville Clark player piano of this type.  There are many
different sorts of Melville Clark players.  Early ones pushed down
in front on the actual keys.  Mine is somewhat later, with the
spring-motor, but with a three-tier stack that engages with whippens
by poppet rods.  I believe there was even a later model that used
a wind motor and circle pouches.

On mine, the spring-motor was in such bad shape (beyond repair) that
I replaced the entire top shelf with one from a Kimball, and the lower
action with a Pratt-Read, resulting in something of a "Frankenstein"
player.

But your concern is primarily with the valves, which is quite
understandable.  The inside valve seat is pouch leather, not likely to
be any good, and it seats against what appears to be a celluloid tube.
I replaced them with the Player Piano Company product, which seemed to
work adequately.  Since this probably is no longer available, the best
bet might be to use an old one as pattern (star-shaped) and cut them
out of good quality pouch leather.  You may also need to replace the
felt between the inside valve surface.

Here is another thing that could get tricky if not done very carefully.
It seems that the only means of adjusting the valve throw is through
the thickness of the outside leather valve seat, which, fortunately, is
just a typical round punching (but with a hole in the center to access
the screw for removing the valve).

As far as the little pouch-pneumatics that control the valves -- that
look sort of like they're mounted on fat Popsicle sticks -- Good Luck!
I'm lucky that mine still works fine on the originals (97 years old).
It would seem quite a job to replace the leather on these.  Extremely
meticulous work, perhaps best performed by a technician with experience
with these and other pouch-pneumatic actions, such as the Shulz.

I would be very interested to hear what other techs have come up with
regarding these most peculiar valves and pouches.  Has there been any
success with designing a different valve?

One other thing -- the piano is one of the best sounding, highest
quality uprights that I've ever heard.  It would be well worth keeping
even without a player.
 
Craig Roothoff
Escondido, California