There are an existing pair of holes in the block near the pan rail between the #6 and #8 cylinders . They were originally used for the vacuum line from the vacuum pump on the bottom of the original oil pump. The new Olds pump has no provision for the vacuum pump and it is not used. Normally, one would just plug these two holes. Except in the case of the a full flow oil filter conversion, these holes are enlarged and retapped.
The original size is 1/8NPT. Drill both holes out with a 1/2 in drill. 1/2in will be the minimum internal diameter of all fittings and hoses in the conversion. Then drill both holes part way with 37/64in drill so they may be tapped for 3/8NPT.
In case you were wondering, there is sufficient extra material in the main web and block side to safely allow for the larger holes.
|Keeping the drill perpendicular to the block mating surfaces may be facilitated by constructing a couple of simple, one time use jigs. Tap the holes with 3/8NPT tap (not shown, but you can use the same jigs after enlarging the holes).|