I have a standard A head that someone installed a 3/8" pipe threaded hole in, probably for a hot water heater. I am not sure if it has any cracks or not. If it is OK (no cracks), I am wondering if and how I could seal shut the fairly large hole and use the head. I don't know if I could welded it shut with my Lincoln SP100 welder and grind down the weld or trying to weld it would ruin it. The head metal thickness where the hole is, is a little more than 1/8" thick. If anyone has repaired large holes like this successful, please post how you did it. I am pasting a picture in below. Thanks for any suggestion on how to fix the hole.