Ok so I am removing my exhaust manifold and I have snapped a couple studs off, I used a 3.5mm drill bit to drill into the snapped studs and used an easy out to remove them, on one of the studs I drilled to deep and drilled into the head, oil then slowly leeked out. Did I drill into an oil gallery or just in the side of the head? And could I just run a 4mm tap through it and Loctite a grub screw in and then install a new stud?