[A26B]

Originally Posted by tomtom72

Tom

Jeff, the hole that is completely "pluged" is the coolant passage in the I/H that exits coolant from the block thru the I/H and then into the tubes.

Tom,

If I'm understanding you correctly, you are referring to the 3rd crankcase vent hole in the injector housings, the other two being completely open or with "washer baffles for the 90 MY.

If so, although it is directly below the coolant outlet passage on the side, it is NOT a coolant passage and DOES NOT "exits coolant from the block thru the I/H and then into the tubes." It is a crankcase vent, just like the other 2, except that it is plugged off in the 90MY. The coolant from the block goes through a passage located between the front 2 cylinders intake ports on each bank.

In that regard, I'm at a loss to offer a reason for the 90 MY front, 3rd vent port being plugged with a solid washer. Adding to the mystery, when the washers were eliminated for subsequent models, the same vent port is open in the inj hsng and the hole is drilled in the corresponding cyl head area.

I think if it were me, with late model inj housings on a 90, I would put "drilled" washers in all crank case vent ports. If they opened it up completely in all years after the 90, then it seems a logical thing to do.