There is an old pipe welder saying that goes" If you want the bottom (overhead) to look like the top, screw up the top" which is somewhat true. With lots of practice, you can make a good looking overhead weld with a DC machine. AC machine characteristics dont lend themselves to making good looking overhead welds. An AC rod needs to have a slightly long arc to keep from arcing out (sticking). For overhead welding, you have to run a very short arc which reduces the arc blow somewhat and allows the metal to stick rather than just droop and fall. E7018 is likely your best rod for AC machine for overhead. As Mark said, with 6011 or 6013 AC rods, you will need to step in and out of the puddle with the arc shorter at the puddle and then long arc it a bit as you step forward. This allows the metal to cool slightly as you step forward then go back to the pudddle to add some more metal. You have to have the amperage set currectly to weld overhead. It has to be slightly higher amperage ( maybe 5-10 ams) than welding flat or vertical for most overhead welding. This is assuming that you are not running too high on the flat surfaces which lots of beginners do. If you set your machine to weld flat so that there is not a lot of arc blow and undercut but still have a fairly flat bead with slight convex surface, then to weld overhead, just raise the amps slightly. This is especially needed with an AC machine to keep the slag away from you rod so it doesnt arc out. With 7018, hold a very short arc and slightly weave the rod, do not step out of the puddle with 7018 like you do with the 60xx rods. Keep a very short arc, and slight weave or just drag the rod. Angle the rod so it is pointed 10-15 degrees toward the puddle and weld toward yourself so you can see the puddle. Keep the rod pointed straight in vertical position if you are welding flat V groove overhead, buy this I mean keep the vertical plane straight up and down but have the rod angle tilted in the direction of travel slightly. Some of this is very hard to explain and much easier to show which is why welding classes are good to go to if you have a competent instructor.
