are you turning it the right way? i dont know if it's a reverse thread, but even tightening it slightly will help break the tension for loosening it.
If you dont have PB Blaster, GET SOME!! The stuff is awesome, and you can get from anywhere, even wal--mart. Worked on a 1948 1ton truck's original exhaust manifold, the only bolt/stud that broke was the one we didnt spray with that stuff. The only thing i've found better is Aero-Kroil, but you have to order that directly from the manufacturer and claim you are a manufacturing company. They will not sell to individuals.
And what kind of breaker bars are you breaking???
