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sodium Vs SS?

I believe that SS valves can handle higher temps Vs regular carbon steel and will hold up under the most demanding applications, but SS valves are expensive. SS is capable of handling the higher heat that carbon steel and/or sodium-filled carbon steel valves. I think the SS Manley valves ran about $20 each for the KUQEFH. Most high-perf and race engines use SS and not sodium-filled that I am familiar with. Manley is well known as the leader in SS automotive valves. Unfortunately, I could not find a website for them with any technical info....


quattro wrote:
> So, the way I read this is that Audi used sodium-filled valves on the turbo cars because the standard
> valves were not up to the job and SS must have been too expensive for production use?
> -glen

I doubt that the cost issue prevented the use of SS. SS is about 10%
_less_ thermally conductive than regular carbon steel. If _that_ has
heat trouble, the SS surely will.

'87 4kq, plain valves
'89 200q, sodium and K26
'64 Falcon, plain valves, 16 hardened seats

> There is an aspect of apples vs. oranges here.  Valve longevity is aided by
> both cooling and temperature resistance.  Given a metal with sufficient
> ductility, hardness, whatever for valve use, then higher temperature
> resistance is better.  This is generally associated with high nickel content
> (SS, Nimonic 80A, ...)
> For better cooling, sodium can be used to transfer heat from the valve head
> to the stem, where the oil splashing about can cool it.  It was my
> understanding that sodium-filled valves were only partly filled, so the
> sodium was cycled from head to stem as the valve moved up and down (or vice
> versa).
>                 .... Kirby   (Kirby A. Smith)
>                               2 x 1988 90q
>                           New Hampshire USA