I would reccomend tapping the aluminum if you can (I don't know how much room you have to work with) instead of using JB Weld, especially on the head, but you could just replace that motor case for not much more than the JB weld would cost.
I would def steer clear of filling with JB b/c after 1 cycle it's going to crack... if one screw is bad i'd get it buttoned down b/c it will be a matter of time b4 you warp the head and start loosing compression
My suggestion would be go to www.mcmaster.com and search Helicoil they have helicoils in a .119" dia (says its a 2-52 thread pitch) I'm not sure what tap you would tap the aluminum to for the helicoil but if you get the kit (kinda pricey there so you may want to shop around but I know they are fast with shipping we usually order at like 4PM and get it next day but we are only like 5 hrs from their facility here in CA) that to me would be the most correct fix besides replacing the block...
I would recommend a kit b/c I think it should have the drill, the tap, tool, and punch to break off the tang...
Nice info. Thanks. Helicoils look exactly like the perfect fix for my problem. I'm in Canada so CA is a little far but I will look into this more because it looks like an excellent solution.
they're great for repairs and also used as locking features...I have used them quite frequently in my year of experience in aerospace...mainly to use them as a mechanical locking element in machined aluminum parts...
One thing to keep in mind if you ever do your own alodining/anodizing you will want to remove the helicoils
Good luck and they may be a PITA since they're so small but who knows they may be easier to work with than the larger ones
I don't know if you have enough material to bother with drilling out and re-tapping. I'd just get a new crank case and not worry about it. They don't cost much. Heck, you may find a local online here at RCNT that would be willing to part with one. I would, but shipping would eat up some $ more than likely.