So I'm starting the cleanup getting ready for reassembly of my 455 HO and I see this hole in the main web. It's the original engine with 115,000 miles on it so I guess it really didn't hurt anything. After looking at it all day and sticking assorted picks in it to see how deep it was (over 3/4 inch deep) I used a bright light and saw threads inside. So I pulled the #3 4-bolt main cap and see light through the hole. I guess an overzealous machinist cut the hole too deep originally. Has anyone ever run into anything like this before????