Awhile back I posted about one of the bolt holes in my aluminum engine block pulling out, well did a bunch of research on different ways to repair it and came up with one I thought was excellent, but not highly know about. Anyways what I used was a product called TimeSert. Its basically a solid cylinder with threads on the inside and outside. The installation kit allows you to drill out the old threads, countersink for the insert, tap the hole, and insert the TimeSert, which brings the hole back to std. thread. I used M10 1.5x20mm inserts for my application. I opted to go with stainless steel (they also offer carbon steel) Their website has a bunch of info about the product as well as a list of sizes avaliable, etc. All in all a pretty sweet fix, so good I ended up doing all 8 motor mount holes, because now I'll have 20mm of thread holding aluminum instead of a hair over 10...

http://www.timesert.com/

I also attached a pic of the finished holes. Hope this helps somebody somewhere down the line!