"Years ago, that was death to the rings and bearings"
Just another old wives tale. I'd be concerned as to why the valve burned. It may have a defective injector on that cylinder and it's running way too lean.
i agree with this as well.
The 6.0 vortec tends to break a rear-most exhaust manifold bolt, for some reason - would an exhaust leak cause the burnt valve?
I forgot about that. An exhaust leak between the exhaust header and the head can will definitely cause a burned valve/seat if you run it too long with the leak. It can also damage the surface of the head where the exhaust port is attached.
