Hole in casting... Fill or not?

Somehow the engine ran with that hole before you took it apart. Just JB Weld it and forget it.

I `D TAPP IT AND INSTALL A SCREW , LOCTITED , THAT DOESNT GO THRU TO THE LIFTER BORE AND FORGET IT , DEBUR THE BORE AND MAKE SURE IT is ULTRA CLEAN BEFORE THE LOCTITE .
I wonder why any one would drill that to start with , unless they were going to do an oil mod , . then changed their mind , would have to lower oil pressure some I `d think.!