The lifter oil feed galley is a hole located along the top of the case between both intake tappets.
86-90 main oil feed path 1) | |
The main oil feed galley is a horizontal passage located along the top of the case beside the tappet blocks and lifters.
It runs from the filter pad to the last lifter bore (lifter for #1 cam).
This oil galley feeds the lifters, cam cover / pinion shaft / hole in pinion gear to the rod bearings and also the gears on cam #2.
In examining the area directly behind the filter inside the gearcase;
You can see the oil path (channels from the filter to the engine).
There is a plug on the outside case in the area of the filter.
The plugged hole is from where the MoCo drilled the oil passage to connect the outlet of the oil filter to the lifters. 2)
After they drill it, they stick a plug in it.
There are other plugged holes like that on your motor where the drilling operation left a hole that had to be plugged.
On 91-99 engines, the oil feed galley is internal from the filter pad. Oil travels to each lifter individually from this cavity. 3) | Rifling hole for the feed galley is plugged outside the case near the filter. 4) |
On 2000 and up engines, the oil feed galley is external. Oil travels to each lifter individually from this cavity. 5) | The rifling hole for the feed galley is plugged outside the case near the filter. 6) |