[Don Moyer]

nyvoyager,

In later late model engines we have seen quite a few cases where what you think is a piece of stud broken off in a manifold stud hole is really nothing more than calcified residue remaining from the end of the stud. One indication of this possibility is if the end of the stud is sort of rounded off instead of showing a clean break. A buildup of calcified crud/residue can usually be cleaned out using a smallish screwdriver (sharpening the tip helps) by gently tapping and turning the blade - sort of like the technique in using a "star" drill in concrete. After cleaning out most of the calcified crud you can use a coarse threaded tap to finish cleaning up the threads. Don