Four years ago when I last did my timing belt, I accidentally overtorqued the lower nut that mounts on the stud. I felt it go soft and it's been keeping me awake at night for years. Well today I removed the tensioner to do the belt again, and it backed the stud out and some threads came with it. Ordinarily I would chase the threads with a tap, but this goes into the oil galley. What can I do? I'm going to be devastated if I lose an engine from a shaving going through it.