sodium filled exhaust valves, for the sbc, or any
other engine.

On a given gasoline, with a certain spark
advance, with borderline knock,,, compare to, replace
normal exhaust valves with sodum filled.
how much extra advance can be used,
how much more power?

 

im not an expert but withcylinder head and camshaft technology these days i dont think theres a need for a sodium filled valve any more,kinda why you dont see them except in maybe very extreme applications..my head guy wont touch them and id trust him with my life.also a sodium filled valve is a hollow valve,a hollow valve isnt as strong as a solid valve...food for thought

 

If the sodium filled valve is lighter than the solid one then it would help in keeping the weight of the valve train down. That would be a positive towards valve train stability.

 

Sodium valves aren't used for more power- they're used for protection.

At high temperatures, the sodium becomes a liquid and moves up and down the inside of the valve, helping to transfer heat from the valve face to the stem so it can be dissipated faster.

Most people consider sodium valves to be inferior to a good stainless steel or titanium one.

 

Exactly. Many heavy duty trucks in the 60's and 70's used these as the egts are through the roof when you are hauling heavy stuff in your f-650with a little 352 or 391.

 

A sodium filled valve is a good thing. Most people dont understand them, which is apparent from this post. They are used for pulling heat out of the chamber and transport it to the guides. Kinda like CoBu seats.

Hollow stem valves are very strong and light and are one way around a lot of rules where you have to run a stock diameter stem valve. The sodium filled valves are not bad either for weight since their atomic mass is 41% that of Iron.

Bret

 

the issue seems to be, valve cooling,,, lets include
copper-berryliun valve seats.

if the issue is NOT valve survival,
how much is to be gained by better valve cooling,
above and beyond what you get with
typical aftermarket cyl-heads.

How often, is an 'overheated' {but otherwise surviving]
exhaust valve, the limiting factor [knock]
in setting the spark advance?

if knock starts somewhere else, at some point there
is no advantage to more valve cooling

thanks for your comments, btw

 

Here's some answers regarding them in LS6 engine development:

http://www.idavette.net/hib/02ls6/index.htm

 

My GMPP LT4 heads came with Sodium-filled valve stems. Supposedly lighter...

 

I believe that was just the exhaust, the intake valve being larger is usually the one were weight is more an issue, since almost everyone runs one PN of spring on the who valvetrain exhaust valve weight really isn't that big a concern even if lift is higher.

 

Perhaps he meant to link this piece of the article instead.

http://www.idavette.net/hib/02ls6/page2.htm

Didn't find the NaK stuff as interesting as the 02' vs earlier cam comparison though.

-Mindgame

 

Yeah, I wasn't sure of the exact page, so I linked the article. I figured some of the background would be interesting as well - though some apparently want a hand-feeding.

The sodium filled valves honestly aren't for much other than getting the requisite RPM required/wanted by Powertrain. It would, apparently, suck having a valve stem break and be exposed to oxygen. Heh.

Basically valvetrain lightness is the reason the valves are hollow because of the LS6 cam and because of the RPM the engine would be turning. Using non-hollow valves would lower the redline 300-400 RPM.

 

Do most people only do the intake when trying to lighten the valvetrain b/c the gain w/ the exhaust is so minimal?
-brandon

 

Sodium filled exhaust valves were used on the old huge piston aircraft engines to help cool the valves. They were using a ton of supercharger boost on takeoff, and wanted to make sure the exhaust valves survived. They were reliable valves, they withstood transatlantic passenger flights in excess of 20 hours on the old Wright 3350 turbo compound engines. What a monster.

 

I believe Porsche was one of the first to use these on their air cooled engines for the same reason, heat transfer under load not weight, being the primary concideration.