[Vic1947]

Finished trimming the oil drain bung and saddled it into the side and bottom of the pan. Similar to the factory setup, the bottom of the threaded hole is down far enough to facilitate oil drainage. Welding cast aluminum to billet is usually a grungy process thanks to the impurities in the casting. However, the GM part is fairly good quality which helped a lot. I also used the bead blaster to clean inside and out where I'd be running weld.

After the bottom plate cooled, I set up the drain plug for welding. You may notice I chose to install the drain in the side of the pan instead of the rear. It appeared that, thanks to the 2" chop, a rear facing drain would have made it impossible to remove the plug. So it went into the side. Used a spacer to stand it off the side of the pan and provide a lip for the weld. After finishing the outside, I flipped the pan over and welded the bung from the inside also. I'd planned to weld around the perimeter from the inside as well, but I happened to look down at the floor and coolant was puddled below the TIG. One of the water cooling lines had sprung a leak, so I called it a night.