The oil pump’s most difficult task is to supply oil to the connecting rod bearing that is the farthest from the pump.  To reach this bearing, the oil travels from three to four feet, turns numerous square corners through small holes in the crankshaft to the rod bearing.
 
The rod bearing doesn’t help matters.  It is traveling in a circie which means centrifugal force is pulling the oil out of the bearing.  The size of the gears or rotors determines the amount of oil a pump can move at any given rpm.  Resistance to this movement creates the pressure. 
 
If a pump is not large enough to meet the demands of the engine, there wiii not be any pressure.  Or if the demands of the engine are increased beyond the pumps capabilities there wiii be a loss of oll pressure.  This is where high volume pumps come in; they take care of any increased demands of the engine.
 
Increases in the engine’s oil requirements come from higher rpm, being able to rev faster, increased bearing clearances, remote oil cooler and/or filter and any combination of these. Most high volume pumps also have a increase In pressure to help get the oil out to the bearings faster.
 
 
NOTE::  Add an extra half quart or so of oil to your engine