Thanks all.

One of my exhaust manifold studs came loose. I realized this after the nut fell off and when I went to tighten it, the stud started spinning. I thought that the threads on the stud were just damaged and that a new stud would thread right in.

After purchasing a new stud though, I have realized that it is not threading into the manifold properly. I can get a few threads started and then the stud just spins without advancing any further. My guess is that some of the threads in the manifold itself got damaged in this process, too.

Looking for some advice at this point. I am not sure if there is adequate working room to tap new threads (or to chase chase the existing ones), but I am concerned that if I try to tap the same size M10 threads that I will remove a small amount of metal such that the stud will not fit tightly when I manage to get it installed.

Does anyone happen to know the thread pitch on these studs for reference? Thanks