You don't have too much to lose by drilling a small hole and seeing what happens. I have anb old jeep and i swear it's held together by jb weld. In my experience, jb weld on oily engine parts stays somewhat pliable. I have a tranny bolt that is threaded into a jb welded hole and it satys tight but I wouldn't want to rely on it to keep oil in an engine.
I say, drill a pilot hole and see what the jb weld does. Then see if it can be peeled out. If so see how bad the hole is. Many times the hole can be repaired with a helicoil insert. Here's a bit about how they work I grabbed off of another site:
Installing a Heli-Coil
A Helicoil is essentially a "spring" of stainless steel wire wound so that the inside diameter of the Helicoil is the same as the female thread you're repairing. The wire used in the Helicoil is a diamond cross-section (instead of round) so that you actually have a set of female threads on the inside and male threads on the outside. The kit comes with an installation tool and a special tap to allow you to tap a new hole for the Helicoil to screw into. You'll need to get the correct tap drill (not included) to open up the stripped hole prior to using the new tap. The Helicoil package will specify the correct drill size.
Simply open up the stripped hole with the drill (be sure to keep is straight) and tap it. Screw the Helicoil insert over the installation tool, coat the outside of the insert with Locktite, and screw it into the hole. It will compress slightly on installation. When the top coil is below the surface of the intake, unscrew the installation tool, leaving the Helicoil in the hole. The bottom end of the coil will be bent in towards the center (which allowed the installation tool to drive it) and this tang must be broken off using a small screwdriver or punch. Be sure to pull it out of the hole using needle nose pliers or a dab of grease on the end of a screwdriver.
You now have repaired the threads to their original size and can use this as you would any tapped hole. In fact, if the piece is aluminum, the repaired threads will be stronger than the originals. This works with aluminum or cast iron pieces.
http://www.442.com/oldsfaq/ofbas.htm#BAS%20InstallingaHeliCoil
Hope that helps!
JF