Nick in cylinder wall but it it may be below compression area.
Thinking this block is junk. Too bad because the cylinder on this one is at most .005 over. It could be used.
I may try bending the tapped guide back and installing a used rod. But I doubt it is worth the effort. Better to spend a the bucks for a new rod and .020 piston to fix one of the two worn out pressurized engines.
Need to check the 31x707 engine to see what shape it's innards are in.