jb weld is nothing more than a epoxy glue with a filler so you can drill and tap it. It will not hold up to the heat, pressure and vibration of the engine trying to anchor a cylinder stud. Best bet is to install a Heli-Coil insert or fill weld and re-tap, or even better - replace the case half.
Be sure to watch the torque when re-assembling. 100-144 oz/in is all they need. Very easy to over torque if going by "feel" alone.