EVO: Oiling & Lubrication - Sub-03K

91-96 Oil Pump (26204-91) Individual Parts and Pics

Pump Assembly with Bottom Cover Casting Number (26487-90)

The oil feed direction into the engine changed in 91.
The initial engine feed on 86-90 models 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.

The gearshaft bushing is no longer used in the body or the cover.
There is an added recess inside the body for a gearshaft thrust washer.

91-97 oil path from pump 1) Parts list 2)

Cover Casting Number (26487-90)

There are 2 versions of this pump although the catalog part number did not change.
The 91-96 version has pump body casting p/n in 26485-90 in the return cavity and pump cover casting p/n 26487-90.
The 97 version has pump body casting p/n in 26485-90A in the return cavity and pump cover casting p/n 26487-90A.

The separator plate, thrust washer, retaining ring and both feed and gerotor sets are identical in each version.
The gear dims are also the same.
However, the gearshaft in the -90A pump is .005“ longer than the one in the -90 pump.
The gearshaft for the -90A pump can be identified by having six hash marks across the top of the gear.




There are two different gearshafts used for the two different pump casting numbers even though the catalog part # stayed the same.
Visually, they are identical.
However, the gearshaft used in the pump with bottom casting # 26487-90A is .005” longer and has six hash marks across the top of the gear to distinguish it.


Separator Plate

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

1) , 2)
photo by Hippysmack
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