Stellite is a very hard metal that does not transfer to the seating metal.
Valves and seats that are made of stellite do not wear at anywhere the rate
that older materials would. Use of hardened materials is one of the reasons
that contemporary engines (such as Toyota's) do not require a valve
clearance adjustment for the first ONE-EIGHTH of a MILLION MILES!!!

Elemental Sodium metal is liquid at temperatures that are common in a valve
stem. It is used in specially constructed valves that have hollow stems. As
the valve heats up, the Sodium becomes liquid. Now the trick is that the
hollow portion of the valve stem is not completely filled with Sodium. When
the valve opens,the Sodium will fill the end of the valve head (inside the
combustion chamber). Here it acts as a heat sink soaking up heat from the
exhaust gases as they exit the cylinder. When the valve moves to seat
itself, the heated Sodium moves to the valve stem area where the heat picked
up in the valve head area is transfered to the valve guide. This back and
forth transfer of heat helps keep the valve cool.

The downside of a Sodium filled valve is that the valve stem becomes quite
large. Because of this and the fact that better materials are now available,
they are not used on smaller bore engines as the increase in valve stem size
acts to reduce the amount of port area (in a critical area) needed to move
airflow in a high RPM engine. But in an inefficient aircraft engine where
heat is a larger concern that power, Sodium valves can be found.

Hope this helps,

Dale Alexander

"Scott" wrote in message
.. .
FOUL!! 100LL has 4 times the lead content than the old 80 avgas and a LOT
more than unleaded auto! Therefore, the 100 octane valves should be
supper lubricated! But, in fact, the 80 octane valve tend to stick if
much 100LL is run through them...

So, somebody answer my question...what is special about 100 octane valves?
The ones I put in my A-65 were Stellite. What does Stellite do? What
about sodium filled valves? What's their claim to fame??

Scott


Matt Whiting wrote:
Scott wrote:

Like I said, MIGHT OK, if there is no difference in heat, what are
the 100 octane valves in my A-65 for? Or more generally, why do they
sell 100 octane valves for A-65s and C-85s, etc. that were certified on
80 octane??? Like I said, I use them, I don't wrench on 'em


Because valves that were designed to be lubricated by the lead in leaded
fuel may not last long when using fuel with no or less lead.

Matt

--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)