Thread question

[evill]

I broke an exhaust stud on my engine. I made a fixture and drilled it out. I re-tapped it to M8x1.25 The new stud threads in loosely for the first 1/2 of the threaded portion, then gets nice and tight when threaded all the way in.

Should I leave well enough alone and re-install the exhaust or should I insert it? I usually use E-Z Lock inserts. The M8 insert is 12mm OD, I'd prefer not to drill the bottom of the head that big.

Any thoughts or comments?


Thanks,
Ed

[juanbenae]

those bury a little less than an inch on a thin flange car, could not imagine other motors have changed much. so it sounds like you may have a half inch of thread "engaging". if its one you can see, and get to easy enough i would locktight it and see how it goes. if it comes out, regroup &redrill.

on the other hand it could be the stud is just bottoming out and tightening. i guess i am no help eh?

[patkeefe]

The rule I learned back in my machinist days is if you can get four full threads of engagement, you're good.
Using your "leave well enough alone" theory, I'd loctite it. If it falls out, then I would go with a Heli-Coil.
Pat