If I were using main studs (instead of bolts), I would probably put some locktite on the threads that go into the block. I wouldn't use the "permanent" type of locktite, probably just the light-duty one. The nuts on top of the studs, I'm really not sure. I used stock main bolts, and I don't think I put any locktite on them. I do remember I put locktite on my rod cap studs before putting the nut on.