So, if you use a magnet to weld a magnum valve cover the manganese in the wire will mangle the weld and require a Magnum malt liquor to quell the frustration. If it's too serious you'll need a magnifying gl*** to see how mangled the magnum valve cover got and how much manganese was mullered up. This will disturb that magnetic personality your car folks think you have, and from there on you can forget that "Magnifying Glance" that Alice Copper taught us.
Stick with a stick welder and you won't get "Wired". It's easy to see we are on lock down and getting crazy.
You welding ****s, ha, ha. Maybe it could be that you have a magnetic personality that causes the weld bead to spatter and get all lumpy? I suggest that you extend your arms and move your body back further from the weld area as you weld. Just joking. I use to weld REALLY good, some ten years ago. Now I can not see as well thru the weld helmet with old age eyes. So, I look at where the weld needs to be, lower helmet, then I weld by memory, my memory must be getting bad also.
To prevent welding bearing to the crank, or welding the gears together in the differential .... always have your project vehicle that you are welding on, so that it is pointing or positioned from front to back, in the North / South position. It has something to do with the magnetic fields of the earths North pole. This also helps the weld beads flow flat and evenly. I never had any problem since I started doing this, when I am welding on a vehicle. Well, I did once, I had the ground clamp touching the Hurst shifter, but thats another story.
Electric current creates a magnetic field - that's how electromagnets work, they're just more optimized to focus the magnetic field. Magnetic fields attract or repel each other, depending on polarity, so running an electric arc in a strong magnetic field from a magnet is quite likely to give you a few surprises.