Sodium filled valves

[Al Powell <a-powell1@tamu.edu>]

I am behind on digests - but I will note that my dad's 1958 Mercedes 219
used sodium-filled valves, which cost $18 each back about 1975!  The
theory as I understand it is that sodium moving up and down the stem
serves as a heat sink and helps to move heat from the face of the valve
into the back end of the valve, which has more metal contact (springs,
keepers) and is in contact with oil which also helps to dissipate heat.

In the classic Mercedes straight-six engine, the sodium filled valves
were used only for exhaust.