WHY ............does anybody know the answer
The picture isn't mine but I swiped it and modified it to show you where to put the chamfer. Just knock the inside square edge off with a file where the red mark is from the oil groove all the way out to the front of that upper front bearing shell. I don't do that anymore, I just remove the front oil gallery plug behind the camshaft sprocket and drill about a .040" hole in it and put it back. That puts a pressurized stream of oil right on the back of the camshaft sprocket and soaks the timing set. Either way will work fine.
