mnl119

Being an engineer, I had to ask...

We all know that our valves on the LS7 are sodium-filled.

Sodium has a melting point point just below the boiling point of water at STP of about 97 C. This means that our valve internals are continuously cycling between solid and liquid phase unless there is some alloying compound that of which I am unaware.

Near as I can tell from available literature this phase change also has a density change from ~0.97 g/cc to ~0.93 g/cc meaning that sodium exands when it melts.

I wonder if this continual cycling/expansion of the valve internals can contribute to premature valve failure (bursting?), guide wear, etc.

Thoughts?

Quick Silver Z

Only the exhaust valve is sodium filled, no?

http://www.fbparts.com/ls_general_charts.htm

http://www.precisionenginetech.com/t...esigns-part-2/

http://www.gmhightechperformance.com...nce/index.html

mnl119

[QUOTE=Quick Silver Z;1578454191]Only the exhaust valve is sodium filled, no?

I did not know that it was only exhaust valves that were sodium-filled. Could explaing why those are the ones with increased failure rates.

Everett Ogilvie

Sodium exhaust valves have been around since the early days of the 327 (40+ years). It has always been only the exhaust valves because they run the hottest (no cooling incoming charge that the intake valves get).

onargaroberts

If I remember my education correctly, the sodium occupies only 60% of the hollow stem. so it "sloshes" up and down the stem. The designed heat flows in the exhaust valve are from the valve face to the valve seat to the cooling jacket and, from the valve head to the liquid sodium to the upper valve stem to the valve guide to the cooling jacket. This works well because it is water cooled engine. Valve guide temperature and wear is a much trickier proposition in an air cooled engine.

There is no fatigue on the valve stem caused by the sodium.

mnl119

Huh. Good to know. Apparently as a previous poster has said these things have been around a while.

I did some more reading and apparently the valves act as a heat pipe. The liquid sodium undergoes a phase change to gas at the bottom, transports itself to the top of the stem where it cools and condenses back to the liquid phase. A very efficient heat transfer mechanism.

Can you tell I'm bored at work today.

CivEngineer

Pretty cool. Heat transfer is definitely not my specialty, but it's always been an interest along with properties and structures of materials.