[Excaliber]

As I understand it some side oiler FE blocks didn't come out "perfect" from the mold and in those cases they weren't drilled to be a side oiler. Still a good block, just not up to snuff for the standards of the day.

It was tough, and expensive, to cast those thin wall blocks back in the day, with a significant percentage of blocks that didn't meet specs lost in the process. That's the main reason the side oiler blocks sold for MUCH more than the easier to cast 428.