What is this thing?
This is a GM Metric Saginaw power steering pump from an '81 C-10. I think a couple billion were made, so SOMEONE has to know what this screw/bolt is/does on the back of the unit. Does it adjust pressure? How do you set it? Is it OK to zing it on and off with an impact wrench? I tried moderate pressure with a ratchet and stopped before I busted my knuckles!