Oil Pump Gear Question

[lycominglou]

on some of the oil pump drive gears they have the seal pressure relief hole that you see in the picture and a lot of the gears, same part number, dont have this hole, also in the -8 accessory case theres a pressure relief hole that goes down from the drive gear to the driven gear and oil can go through the center of that driven gear through the pump cover and back into the sump and thats a very large passageway. anyone know why the hole is in some gears and not others? this is a 3562 gear thats in the -8 case.

 

[lycominglou]

 

[nrpetersen]

 

[lycominglou]