fwiw, Loctite brand foruma 222 (purple) works pretty well for me. Most "blue" threadlocker is meant for larger bolts (larger than 1/4"), so it doesn't hold well on smaller bolts. Some red is also that way (Loctite makes a ton of different forumlas that are "red").

They have high heat, oil resistant forumlas that will easily handle anything our engines throw at it.

fwiw, I also ditch any gasket, use bare metal-to-metal, and usually use a split washer under the bolt head. Sure doesn't hurt any.