I keed, I keed. This is the kind of sh*t that makes aluminum hard to weld. After you have done all your cleaning and cutting, clean it again. 3 times. The guys in welding shops where I worked had a heck of a time welding Aluminum oil pans. My advice is to weld it as best you can after extensive cleaning, knowing porosity will ensue, then drill out eash hole, and try again. Then repeat. Good luck, Duster. Maybe make a template for the steel oil pan you could end up building before you do anything to the aluminum pan.
