Interesting theory.
During engine operation, there is a brief moment between the exhaust stroke and the intake stroke where the piston actually draws a very small amount of exhaust gas back into the cylinder. This combined with the vacuum created when the valve does shut, will draw a mixture from the exhaust to the engine. With a full exhaust, the gasses that could reach the head are no further than the cat. With open headers, you will draw oxygen rich air back into the exhaust, and up to the exhaust port. This Oxygen will raise the temperature substantially. The burning of an exhaust valve can only occur when the temperature is raised above the melting point of the valve metal.
Take care
~Chris
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Retired Moderator
MustangNet
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JimPorterRacing
RACECAR spelled backwards is RACECAR
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