The plugs are installed with a sealant like red LocTite, and the repair is pretty much leakproof. If the casting is at least 1/4" thick they work pretty well. Yes, a hand drill motor is used, with a piece of square key stock with evenly spaced holes in it as a drilling guide. The holes are drilled slightly over 1/4" apart, threaded and plugged, and then holes are drilled and tapped between the plugs after the first set ofl plugs are ground flush with the surface of the repair. The result is a series of "figure 8" shaped plugs that overlap and seal against each other. The repair in the photo must have been done by Ray Charles or Stevie Wonder! A somewhat modified version of that procedure is called "Lock-N-Stitch". Look up the you tube videos on that system. The L&S process tries to make crack repair "idiot-proof". Oldtime machinists usually had enough common sense not to make rookie mistakes with the more primitive repair plugs.
www.youtube.com/watch?v=Pq0wfU4ZaKkJerry
