Mitty, I have seen a guy weld Aluminum Pop cans together with the Aluminum propane gas welding rods that I now use. Its a trick, but he did it, you need to be quick and in this case most of the heat goes to melt the rod and then you very quickly sort of smear it on the cans with the rod, its nuts to see, because the propane flame will burn through the thin Aluminum cans as fast as you can blink. I make mufflers with these rods, but I use .060" thick Aluminum as a Minimum, because as you know a muffler will have the manifold section that bolts on to the engine and the main body will be thinner and you need to account for this, as you know, when spreading the heat of the flame around to get the various thicknesses of material up to the necessary temperature of these crazy rods. Different Aluminum alloys act differently as you can guess with these rods as in all welding. Sometimes, only sometimes, the rod metal will flow like solder, but don't expect it to. What amazes me sometimes is that you can melt this rod metal on To Aluminum and then brush it off with a stainless brush or a rag or whatever and there will be no residue, it all comes off. With lead solder you will always see a thin coating of the solder remain. These rods can test your patience, but it can be done, but again, you are working with something that is pretty hot and you sure don't want to get careless, distracted, etc. I keep the necessary welding of my muffler designs to a minimum and I have the hang of fusing the Aluminum and the rod metal alltogether into very stong joints. A drawback is that the rod metal is heavy, so I grind any excess off for looks and to remove the weight. It seems that the process is not always exactly the same as the last time you did it, because of differences of the Aluminum that we scrounge up. One trick I picked up is small but useful at times. If you weld on one section of a muffler and then let it cool down before doing a later weld, it seems as though the first part will need to be brought up to a higer temperature than when welded, before it will melt again, and I use this to get a second weld done without melting the first. This is where the persistance and the observation of a modeler comes in handy. I also use a Stainless welding rod with the coating removed to poke and push the molten rod metal around where I want it, it gets crazy at times, but I get determined to get my mufflers made. I just made two Pitts style mufflers, one for an OS .20 and an Enya .19, you can't buy this size in a Pitts muffler. Yes I have screwed up a couple in the learning process. If anyone wants to seriously try doing this, I'll try to help.