I'm rebuilding a Wurlitzer 105, and I'm having issues with the stack.
This the first time I've worked with Wurlitzer unit valves.  I've
rebuilt all of the unit valves, and they all test fine on the bench
with steady vacuum.  With all of the valves installed, the stack is
tight with no leaks under steady vacuum on the bench.  My problem
occurs when I try to install the stack in the organ.

I'm not getting steady vacuum from the organ's pump.  My vacuum from
the reservoir measures between 27" and 32".  When I attempt to install
the stack, I lose significant vacuum.  With all of the valves installed
on the stack, I'm measuring 10" to 12" when the stack is installed in
the organ.  Any thoughts on why I'm dropping vacuum and what I need to
do to stop the leakage?

Steve Dean