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SR20DET heads are nearly identical to their non-turbo counterparts except for one thing. The turbo heads have sodium filled exhaust valves. Sodium filled valves have a hollow head and stem filled about 60% with Sodium. Sodium has an extremely low melting point (about 100 degrees C) and boiling point (880 C). In a hard-running engine, the valves are hot enough that the sodium in the head of the valve vaporizes and travels up to the cooler stem where it condenses back to a liquid again. The phase transition from liquid to gas absorbs a lot of heat, and the condensation dumps the heat in stem where the lage metal-to-metal contact between the valve stem and guide transfers that heat to the cooling system. Without this heat pipe effect, vastly more heat would have to be transferred through the valve seat. Too much heat through the valve seat, and you get a burned valve.
What is the lbs value of MM inner springs? Those sound like a good improvement. The question is, do heavier inner springs cause valve to spin and creates more erosion than stock configuration.
What is the lbs value of MM inner springs? Those sound like a good improvement. The question is, do heavier inner springs cause valve to spin and creates more erosion than stock configuration.
That must be why the keepers don't pinch the valve, they allow the valve to spin independently of the spring and retainer.
12-30-2014, 08:21 PM
