By all means, do not adjust the spill valve on the Ampico pump for the
sake of changing the speed of rewind.  Yes, it can change the speed,
but it will also change the intensities (its purpose) and cause the
music and other piano functions to deteriorate (either too loud on loud
passages, or so soft that it drops notes).

Getting the spring tension too strong, can result in severe damage to
the pump.  If you are in doubt, have an Ampico expert set the pump
pressure for you.  The pump pressure (vacuum) should be 20" with the
modify switch set at medium and all intensities activated.

Once this is accomplished, set the second pump pressure when the modify
switch is set at brilliant.  It should read 27" to 30".

Bruce Clark