Need to replace a head exhaust stud - what is proper thread pitch for both ends of the stud? Are they the same on both ends? (I'm hoping the threads in the head aren't bad...)
TIA

1.25

M8-1.25
If the threads are bad use a timesert, don't use a Helicoil.

If the threads on the stud were galled, or the stud/nut doesn't seem to tighten to full torque, then the threads are striped.