As our VWs get
older it will eventually begin to lose oil pressure. And we may notice
that our oil light comes on earlier near idle, and takes longer to go
off as we accelerate.Some might think that this is the oil pump is going
bad. This is rarely the case. As the engine wears, all of the oil clearances
grow larger, and the oil flows through the bearings (etc.) with much less
resistance, and the result is less oil pressure. Of course the ultimate
or eventual solution is to rebuild the motor.
The oil pump is driven by engaging in a notch in the end of the camshaft.
This puts the oil pump body in very close proximity to the 3 rivets or bolts that hold the camgear to the shaft in the 40 HP 1200cc and 50HP 1500cc motors.
If you were to try to install the larger volume stock oil pump from the 1600 cc motor you would find that it hits the bolts.
In the 1600cc motor there are 4 rivets in the gear that have been moved outward and the gear is dished to allow room for the deeper pump body.
The 1200cc motor could benefit from the 20% larger pump from the 1500cc motor, but the 1500cc and 1600cc motors have to use heavy duty aftermarket pumps for more volume.
These are readily available. Another thing we need to be aware of is that the high performance camshafts all use the older style 3 bolt flat cam gear.
This means that even the stock pump will no longer work, and a heavy duty pump made for that application has to be used.
little bit of information in mind could save you time and trouble if you
are upgrading your oil pump. Just a note: Using a heavier straight weight
oil could also bring that oil pressure up a little.