I'm at it again. After removing the heads, I was inspecting the block and noticed the letter "B" stamped into the mating surfaces on both sides. Can't seem to find any info on this. I'm thinking the block has either been decked or this is another bit of Olds info I need to learn about . I'm beating my head against the wall!!

 

I seem to recall reading that Olds stamped the block for the range of bore size. For example, bore size plus or minus whatever amount used a A piston, next dimensional range would get a B piston, and so on. For the W-30 cars with the “factory blueprinting” I think they used pistons/bearings that fall into the next oversized for extra piston to wall and bearing clearances. No way would they have had a guy in a white lab coat (Dr. Olds) lovingly measuring each and every part.

 

As Matt points out, Olds marked the block for bore sizing to match piston selection.

 

Once again thank you everyone for the help. I was hoping the block had not been decked. It appears the valves made contact with the pistons. No significant damage to the pistons and heads are being rebuilt as we speak. Still very concerning. It looks like whoever got a hold of this motor really screwed up the top end. I have to replace cam, lifters, push rods, and rockers. Still concerned about piston to valve clearance.