Just the dose of pure nitrous is not what hurt it, because without the proper amount of fuel to go with the added oxidizer, you are not doing anything.............BUT.........in this instance, as obviously they were "tuning" on the car, I would bet my bottom dollar the tune was rich. So when they hit it with all the nitrous, the tune got "clean" for a split second(you hear the motor rev)it made some real power, was over timed for that power and pushed a head gasket out.

Monte