Here's a photo of the stud.
You can see that the O-ring groove is the weak spot, the threaded part at the end is there to put that nut on which stops the stud coming loose from the bearing and falling into the IMS, causing all sorts of problems of which a match and a gallon of fuel word sort out nicely.
Been drilling out broken manifold studs today and re-tapping them. Dreadful job.
