We have sold the stuff for about 30 years. Loc-tite is an anerobic compound that cures in the abscense of air. It needs to be on the threads and in contact with other threads to work properly. It's not impossible to put it on the underside of the heads and have it hold, but there would need to be a lack of oxygen for it to cure. The preferred method is on the threads.


-Shoot Straight, IM