Factory Block Oil Passage Drilling

The thin shiney ring in the hole is one of the small steps in the drill size. Sorry that it is hard to see. These steps decrease in size at each step, and decrease from each end and in the mains oil passages. Toolmanmike gets the prize here, as he said that step-drilling was how it was done, in this thread:

http://www.forabodiesonly.com/mopar/showthread.php?t=327115&highlight=lifter

This particular gallery has a rough segment near the middle, where it looks like the final drill step was not done in the rough cast gallery for the drilling from the back. It is still >1/2" ID so we did not drill it out; but this explains the unusually small lifter oiling hole in the thread above; it was just not properly finished out inside the gallery. (We found that undrilled segment after all the other drilling and an extensive cleaning of course!)

Based on this, it may be worthwhile to inspect the galleries and all oil passages for completed drilling operations end-to-end for critical racing use.