[pyoungbl]

My experience, limited as it is, is that cast aluminum is a real bitch to weld to. There is something about the molecular structure of cast metal that just does not lend itself to welding. Smarter guys than me have warned me about this. I can do TIG, MIG, and stick but I'm not warm and fuzzy when it comes to cast aluminum. I have considered brazing to the aluminum just to build up more metal for the tapping process. If you figure out a way to TIG a nipple you will be my hero, please post your results here.