Dear Eli,  Greeting from The Bronx,  In regards to how to rebuild an
Aeolian plastic valve unit -- you don't!  The operation would be too
labor intensive to make it financially cost effective.

The creation and implementation of the unit valve design was
adopted by many of the larger mechanical instrument manufacturers:
Operator's Piano Co. (Coinola),  American Piano Co. (Ampico, from
which the Aeolian plastic valve was adapted), Wurlitzer, etc.   All of
these companies adopted the unit valve idea with one thing in common --
keep the instruments playing with the least amount of down time and
ease of replacement of parts.

A route operator or technician (sometimes even a piano tuner),
would carry an assortment of replacement parts for various makes of
instruments.  Upon replacing a valve, the old one would be thrown away.
The quality of the wood used for the valves wasn't always the best;
Ampico valve blocks were assembled and then coated with heavy shellac
to negate any problem relating to porosity of the wood.  Even Wurlitzer
unit valve blocks were known to become porous with age.

Replacing the Aeolian plastic valves require removal of the valve from
the pneumatic deck board.  As the valve was secured to the board with
Duco Cement, one is required to exert a considerable amount of force to
remove it.  Either the valve suffered fractures or the deck board
would lose chunks or splinters of wood.  It was customary to replace
the valve using Duco Cement, as the generous application of cement
would fill any gaps or voids created by the removal of the old valve.
Hope this helps.

Sincerely,
Dale F. Rowe
Bronx, New York