Heli coils were invented in the 40's or so and the patent expired not so many years ago. They do work but you must be sure the end of the coil is one thread below the surface otherwise the coil will lift and jam the bolt thread. Also be sure the tang at the bottom is broken off and that end didn't come out of the thread. The original thread can start to crack and everything will pull out if the coil is barely below the surface so one thread below the surface is a must. When installing the bolts, be sure they start without cross threading as the sharp end can catch the bolt.

Time serts can't be used when you don't have enough material around the hole making heli coils the only option. The time serts ( or at least ones that look like them ) I've used accept a regular tapped hole a size or two larger. The hole must be drilled larger than you normally would use because the external threads on the time sert are pretty shallow.

Are you sure the tap was a special profile? The selling point of TS type inserts I've used is that standard taps can be used.

Tap Magic makes 2 kinds of tap fluids that work well.


" blue devil headgasket sealant, "

Yes, the stuff works, I've seen it used on a few cars with combustion to coolant leaks and the results are amazing. Basically the stuff is " Sodium Silicate" sometimes called "Water Glass (used to dip eggs) " and a few other chemicals , . The SS stays in suspension in water and does not fall out / clog small passages. What happens is that as the mix hits air the SS starts to solidify plugging the leak.

This this chemical had been sold by Moroso for years to racers with porous aluminum cylinder heads and crack repair equipment companies but, they would use it with the heads off.