The pumpheads that we call "marzocchi" are all of "balanced end plate" design.
a normal pumphead is built with clearances to allow for heat expansion so that it wont seize. this clearance allows pressure to leak past the
gears reducing the efficiency.
if you have taken a balanced end plate pumphead apart you will know that the gears have a block either end of them that floats in the body. the
complex seal design at the block ends applies pressure to these blocks. more operating pressure sqeezes the blocks harder, this gives the head
a "variable tolerance" so it can be more efficient all the time. the heads as standard have one outlet port [against the center block]
and two inlet ports [one in the end and one on the side]. if the end plate is redrilled to give another outlet port on the pressure side you have two oulet ports.
[you could turn the plate around so the inlet port is on the outlet side but that would reduce the inlet volume of oil, and destroy the pressure
balance effect].
having two outlet ports increases the maximum flow the head can produce if you run it fast enough [more volts] to exceed the flow that one port can handle.
although pressure does rise as we put in more volts, it is actually more flow that makes a car lift faster.
the pressure "that goes to the other end and back to the tank" is what makes the balanced end plate effect work, and it bleeds back into the tank to release the blocks at low pressure.
i guess this is a worthwhile modification over 60 volts, but under that the standard port will handle all the flow the head can produce.
[note that heads made for the lowrider market do not have the same port layout as the oem mara'z made for "standard" pump units.]
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