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Dcmgt,
It's not so much that Ti valves are unreliable they are just not as long lived as steel valves. Ultimatly it is the heat cycles that lead to failure just as much as total miles. But the real reason for not using them is that, for the most part, your engine does not need them. Although intake valve accelleration is important to output the same cannot be said for the exhaust. This means weight is not so important. But there is still one more issue here. A sodium cooled valve will have less tendancy to bounce than you might think. Because th sodium sloshes up and down it acts like a damper so even though the valve may be about 10 -15 grams heavier it does not act that way in practice. Couple this to a less agressive valve action and you can see that the sodium valve will not be a limiting factor in terms of output but it will be more reliable. I have a Cup
Car (2002 Dodge Intrepid) I have rebuilt the engine so it can survive 24 hour races. It uses Ti intake and sodium cooled steel exhausts.
DV
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