I am replacing the headers on my O/T Dodge pickup with a 360. One of the exh manifold studs broke off flush with the head. It is one of those that goes into the water jacket. After much work, I was able to drill it out and re tap the hole. The new stud screws in nicely, but I am afraid it is just a little on the "loose" side. I am pretty sure a heli coil would never seal here. My thoughts are to take a q tip and fill the hole with #3D Permatex Aviation Form a Gasket sealer, dip the stud in the same stuff, tighten it securely, and let it set up for a week or two before adding coolant and firing the engine. Any body ever done this and think it will work OK? Or have a recommendation for a different product to use? Maybe old style gasket shellac? Thanks for any useful advice.