EVO: Oiling & Lubrication - Sub-03K

The oil feed direction into the engine changed in 91.
The initial feed on 86-90 engines is directed straight out of the oil pump into the bottom of the cam cover.
On 91 and up engines, oil is routed from the oil pump into the oil filter pad and then into a horizontal feed galley in the top of the gearcase.
This removed the need for the oil to return to the pump from the filter as in 86-90 engines.
Therefore, the filter return port on the -91 pump was removed. It has only one feed fitting in the front routed to the filter pad.

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The 91 oil pump only has only 1 separator plate.
The Moco got rid of the second plate and the spring washer as was in 86-90 pumps.