For what it's worth, I work in a machine shop making jet engine parts day in and day out. We work with aluminum a lot. The only reason aluminum is heli-coiled (we use key-serts which are better) is for repetitive bolting and unbolting of parts together. The aluminum threads will hold up just fine as long as you don't get crazy with over torquing and strip them out. I think the TFS quality issues have all been resolved long ago, but I still have heard people who have used both swear by AFR.

And the reason people have had problems with heli-coils pulling out of the AFR heads is probably because they had bolts that were too long and were bottoming out in the holes which would easily pull the heli-coil out. Just a guess.

Thanks for the info. I'm not a machinist, so I wasn't aware of that.

As for TFS problems, I have 3 customers who purchased the TW heads when they were new a few years ago. One guy had wear problems because the heads had been assembled with steel valve guides instead of bronze. TFS replaced the parts under warranty. My other 2 customers sent their heads back for the same reason, and TFS took care of them as well. Since then, the TFS heads haven't caused any problems. TFS now installs bronze valve guides in their heads.

I understand some other people have had issues with the TFS heads, however in my indirect experience, the guys here haven't had any serious problems with them.