I have been restoring a number of these Aeolian players recently.
I have both restored the original blocks and purchased new ones from
Denis Wilkinson.  The new ones are the way to go.  The problem from
the factory in these Aeolian players has always been the valve itself.

1) The factory valve is of sponge neoprene of the kind that deteriorates
at its surface within months.  It is the problem with the olden days of
the 70's when Durrell Armstrong tried to get us all to use sponge
neoprene for all valves.  The stuff seals 100% when you first install
it, but after a few months or a year or two they seep like a sieve.
Also, they compress so you can never really regulate the valve travel
because travel changes with the pressure in the stack.  Also many of
these instruments have valves that come loose from the valve stem, and
then they are just a flat-out 3/8-inch-diameter leak to the system.
You get a couple of these leaks going and the piano can go years
without playing at all.

2)  The original regulation of valve travel ran from 60/1000ths to
90/1000ths and that allows for a huge amount of pressure lost each time
any valve is in motion.  This is why you could adjust volume at the
pump and get no playing on the piano softer than mezzo forte.  Anything
lower in pressure dropped out notes.

The new valves by Denis Wilkinson are a close grained solid silicone
that does not compress easily.  The valve travel is correct for soft
playing (around 30-35/1000ths).

When I restore these players they play better than they did when new,
they take so much less work to play (especially with my new bellows
cloth installed as well).  They are able to play softly and pedal like
a dream.
 
I glue them on with plastic glue, PVC-E or Tacky glue.  First, however,
you must sand the open side of the block to rough it up enough for some
tooth for the glue, and also sanding flattens out that side as they are
not always 100% lined up when glued together.

I am able to restore these stacks very economically.  Some of them need
pneumatics recovered, some do not.  Send yours in and we will give you
a deal on it.

D.L. Bullock   St. Louis
http://www.pianoworld.us/