Occasionally you might run into a late model A Ampico which has
the B type pedal valve unit.

If you have re-valved and re-pouched the unit and find that the
sustaining pedal doesn't do what the B model sustaining pedal is
supposed to do so beautifully -- that is, return to rest quickly --
check the seal over the sustaining valve port.

Even if you have replaced it, be careful to seal around the edges
of the material.  Even the slightest leak here will keep the unit
from functioning properly.

Tim Johnson