Chainsaw Repair

This is the only clamshell-ish saw I've worked on, so I'm not feeling too confident with this problem I've run into.  I have been attempting to rebuild a Husky 350 that developed an air leak between the aluminum bearing holder and the plastic crankcase because one of the screws loosened and fell out.  The bottom holes in bearing holder are not tapped for machine screws on these saws; the screw threads are sharp, and they just bite into the aluminum casting.  I cleaned it all up and put it back together with the appropriate sealant, which went swimmingly until I put my torque wrench on it to tighten it to spec.  Two of the four screws stripped out of the casting before reaching the low end of the specified torque range.  So, the casting is toast and now I'm worried I'll ruin the replacement I just ordered.  In retrospect it's not too surprising that this might happen; every time these screws are removed and replaced, they could cut new threads into the casting instead of slipping into the old ones, and that would quickly weaken the holes.  Can anyone advise me how not to repeat this little disaster? 

Yeah I'd try a larger screw before trying new parts. Worst case you are where you are now.

haven't ran into this problem yet but on recoil screws and such in aluminum or mag I use time-serts. work great and haven't had a single one come back yet. they are expensive though. each insert is about $3 plus an $70 tool set to install them.

Huztl.... Or convert them over with heli-coils . All four. NOT a disaster! Either an opportunity to learn some shop skills, ie. Heli-Coil's OR learn about cheap aftermarket parts! Both are either a PITA or lots of fun depending on the mind set & real time needs.