Using 4043. I've tried cleaning passes, aluminum-dedicated SS brush, acetone, repeat, but doesn't seem to improve much. I find I'm having a hard time getting the material to puddle. I've tried preheating the part to about 200* but it dissipates heat so quickly it's difficult to keep it hot - it seemed to help a little though. I think I'll throw it in the powder coat oven and get it up to 400* or so and see how that goes. I'm also only on 110v as I don't have 220 in the garage so that's probably not helping things - running it at about 140A. The casting is about .250" thick so 140A is probably a little cold for aluminum. I may have to try it in the house on 220, crank it up and see how that goes. I really need to scoop up a manifold to practice on then give the preheat a shot, maybe with more amperage, and see how it goes.