Printable Version of Topic

Posted by: ruddyboys Jul 22 2004, 12:10 PM

Does anyone have a pic of what the sodium filled exhaust valve look like. I have to pull the engine to replace a valve spring, again, so I figured I would replave a exhaust valve the has a little damage to the top.

Posted by: Jake Raby Jul 22 2004, 12:35 PM

Sodium filled valves have a very small dimple right in their center, its maybe 3-4mm diameter.

Posted by: Dave Bell Jul 22 2004, 12:47 PM

I don't have any pictures, but there is a nice summary of the multiple advantages of the Sodium filled valves at.

http://www.ganioglu.com/supar/sodyum/sodium_filled.htm

Reminds me of a MIG/TIG welding class I took about a year ago.. someone had donate a couple boxes full of partially finished and blank titanium valves and other students had welded some together as practice material... what a shame! There were still lots left though... an man were those babies light.

- Dave

Posted by: ruddyboys Jul 22 2004, 12:53 PM

Mine don't look like these from PP.


Attached image(s)

Posted by: Jake Raby Jul 22 2004, 01:56 PM

No benefits of Sodium valves in the Type 4! Not that i have seen...

Nice explosions though :-)

Posted by: Demick Jul 22 2004, 02:18 PM

I would think that you should be able to replace a valve spring with the engine in the car.

Posted by: Headrage Jul 22 2004, 02:22 PM

Any reason why you can't go with stainless in a stock motor? Reliability issues?

Posted by: Jake Raby Jul 22 2004, 02:34 PM

Stainless is BETTER than sodium!! I build 20,000 buck engines with stainless valves! (they are severe duty valves, however)

Posted by: Dave_Darling Jul 22 2004, 02:37 PM

The valves in the photo do not appear to be sodium-filled.

Jake has never seen a benefit to the sodium-filled ones, but he does not build stock engines. Porsche decided that they were a good idea to help keep the exhaust valves from burning. They help transfer heat from the valve face through the valve stem to the valve guide, and from there to the cylinder head where it can (hopefully!) be radiated away to the cooling air.

I myself would strongly consider the sodium-filled valves on a stock motor. If, however, I were paying a pro (e.g., Jake) to build a motor for me, I would listen for his advice and pay attention to his recommendations for that specific motor.

--DD

Posted by: Headrage Jul 22 2004, 02:56 PM

I have spoken to several different shops about going with one or the other and it seems to be about 50/50 either way. Based on the experience of builders like Jake and others, dosn't it make sense that if stainless works well under the rigors of racing that they would do well for street use?

Posted by: bperry Jul 22 2004, 03:59 PM

I have no idea where I originally heard this but,
I always thought that the purpose of the sodium was to enhance
valve cooling by using the phase changes of the sodium changing back
and forth between solid and liquid states.
I thought the theory was that it went liquid during the combustion
cycle then at some point before the next combustion cycle it
turned back to solid.
Since it consumes quite a bit of energy to change states that you
got a slight cooling effect for free as the sodium transitioned back
to solid state.
It always sounded like a good theory.
Maybe it only works at low engine speeds like at idle?
and is only needed when running hotter running cams like the stock
FI cam?
That would explain why racers would never see any difference.

Anyone else ever heard of this?

--- bill