I was once told by one of the resident "experts" on this forum (who has not been around lately) that I should replace my sodium filled valves with stainless. However after visiting the local RSR racing mechaninc (who is machining my case and inspecting my heads), HE said that he goes out of his way to FIND sodium filled valves for race engines. He said that on Air-cooled engines, the sodium helps pull the heat from the heads.

Any comments or suggestions regarding sodium vs. stainless?

I also heard that a simple change from two-angle to three-angle valve seats can increase flow by more than 20% with no other changes to the heads.

Good news is that I should be re-assembling the engine without the deck height problems over thanksgiving weekend. Hope to have it running by Xmas.

Stu

I'll give you a little hint. Aircraft engines use sodium valves.

I know Chevrolet used sodium filled exhaust valves on their Corvair Turbo engines.
Can't see they would bother if it didn't help dissipate heat..

Sodium valves = good Old school tech , they withstand heat better then stock valves ,
Stick with S.S. valves , they are better & cheaper , Bill D.

As long as the engine is well maintained and not abused you should be fine. The sodium valves installed by the factory in the past had a bad reputation of dropping the 'valve head' into the combustion chamber. However I am not sure if there was any abuse or neglect involved in those cases. But if you keep track of your valve adjustments regularly, you will get a fair warning if the stems are stretching before they would actually fail.

But as mentioned above ........ newer SS valves are inexpensive, plentiful and reliable.

I, also, will give you a little hint. STAY WITH THE SODIUM FILLED VALVES!!!! Rsearch it and I believe you will find the sodium provides much better heat transfer than stainless steel. If you have not had any trouble with the sodium ones and they are in good shape, stay with them. Never had any problems with seats or dropped valves on either my 914s or Alfa Romeos. Always rebuilt with sodium ones.

The sodium allows heat to be transferred from the valve edges up the stem via internal stored sodium and out the valve train, or something like that. Itis also used in some solar energy systems as a storehouse of heat until it is needed to generate electricity during the night time.

Steve Hurt

In theory. The sodium does keep the heat out but I would answer the question this way; 40 year old sodium valves - bad. New - good. Finding them? Not so easy. So there you have it. SS is probably a close second.

Also, is yours a race engine? VW purposely made the later engines run hot with the cam they used. You can probably change cams and take more heat out of the equation than the sodium filled valve stems.

What could go wrong? Drop a 40 year old valve in your new heads, destroy a head and piston and more than likely a cylinder.

I call on that thinking.
Rob sounds like your drinking the Raby Kool aid.
If you tortured over heated & neglected your motor, sure after a few DECADES
your chances of a seat or stem failure are bound to increase.

But if you provide appropriate maintenance, Oil, valve adjustments cooling and dont spin that motor beyond its realistic operating range
(continuously )
I believe you are better off with a technology that was designed for the engine than one that was not (Im pretty sure SS was around in the early 70's?).
As for new valves being hard to come by, IDK I havent had to source any recently.
But they will ALWAYS be more expensive than SS.
False economy.

I thought a bit of raby's thinking was to do with the keeper design which was better on newer as valves

BTW this was beat to death here a few yrs ago.
HERE

Sodium valves transfer heat to the valve guides. They are hollow and filled with sodium. Sodium of course is corrosive to metal and as mentioned sodium valves probably have a limited life (20 yrs?). Many Ferrari's came with sodium valves.

As far as 3 angle valve guides. The three angles are fairly normal in production cars now. Valve guide machines cut the three angles with a single pass using multiple angled blades. A 20% increase in flow is probably a far stretch. Many racers now go for a 5 angle cut or an infinite flow cut (think 1/2 of a bell curve).
The multi angle cuts allow air to flow around the seat/valve with less turbulence resulting in higher flow at lower valve lift.

In addition to having a multiple angle valve seat you can also have the valve seat face back cut. Looking at a valve you have the normal 45 degree cut on the valve face which seals on the valve seat. A back cut is added to the top of the face so air flowing out of the intake port flows easier over the valve.

It is widely accepted that valve seat cuts should not exceed 15 degrees between cuts. When atomized fuel tries to go around an angle greater, the fuel tends to drop out of suspension. Most three angle jobs coming out of the port are 60/45/30.

The Sodium in the valves transfer heat away from the valve head by reciprocating up into the valve stem allowing more than the typical amount of heat (around 20%) to be transferred through the stem to the guide.

I think they serve a purpose and are beneficial where the amount of heat generated can't be handled and transferred away adequately by a solid valve. I have seen no evidence of this issue when S.S. valves were coupled with the appropriate seat and guide materials, even on high compression race engines running high egt's and long cams that hold the valve off the seat much longer than a street engine cam.

Over the years I have seen countless examples of failed sodium valves. Were they old? Yeah.
Were the engines abused? Probably.

New replacements are available and relatively expensive compared to S.S., though I might be hesitant to use them with the O.E. valve seats, but that is moot point with me as I never build T4 heads with the O.E. seats.

My attitude about sodium filled is this; If a customer wants to use new ones in a pair of stock heads that I'm building I'll install them. But if they plan to up the spring pressure for higher revs, I won't.

I know, there are plenty of examples of folks using sodium filled exhaust with dual springs, so obviously they don't all fail in that application. But enough have that I can't see the value in taking the risk when S.S. coupled with the proper valve seat material and modern guide materials do a fine job of handling the heat.

I would imagine that aircraft engines utilizing sodium filled valves have a regular replacement interval that is waaaaay less than 35+ years.

The stock heads already have a three-angle job on them. Check your manual, and you'll see.

--DD

Not true, I see many modern heads, and I can say that the one and two angle cut is still prevalent. Even the latest DFI 9A1 Porsche uses them on the exhaust, though the intake is more sophisticated than that. The Cayenne V8 only has 2 angles on in and ex seats.
Honda, mazda, bmw, vw, porsche, mitsubishi all still use very simple one and two angle seat profiles.

And most 4 valve heads are designed with throat size/valve size ratios high enough that there is no way a total of 5 angles can be squeezed in.

Just to continue on the thread hijack, I attached a link to an article from my website about a Miata head that picked up 26% ex flow from just a seat cut. The page has a link to the flow data.
http://www.hamincgroup.com/blog/services/valve-seat-cutting

What does the inside of a sodium valve look like?

hollow with sodium in it

That is unheard of, wow. Looks like his first pass is a straight cut into the throat so he is opening the seat to 89% of the valve dia. That make sense. Most local machine shops are just going to do a simple 60/45/30 when asked to perform a performance cut. So I guess when you ask for a "valve job" you really need to have a performance shop perform it vs. a rebuilder.

Oh, I see this is your shop. So to get back on topic, what flow numbers have you seen from the porsche heads? And what work do you include in a "seat cut" ? For what Price?
Your bench looks familiar...you do work for Jake?
Impressive work Len!

Len does all of Jakes head work, but he is independent from Jake.
I used a few sets of HAM heads, have a set on the bench right now, top notch work.

Everybody thought the exhaust valves with a divot on Porsche heads were sodium filled but both factory paper work and destructive testing is showing that most SC and 3.2 valves are not sodium filled.

Nope... HAM Kool Aid. The instrumentation that is in my car was there with the stock engine, the 2270, and now the 2432. Both run dramatically cooler head temperatures than the stock motor. I would never trust either of the latter two to 40 year old valves. Anyone who knows me knows that if Len would have suggested new sodium filled valves they would be there.

To paraphrase Jake, You are the designer of the engine, you are responsible for your decisions. Go for it and let us know how it works out. If it works out, great. If not you can start your own pile of shame parts just like Jake. Good luck.

another thing I don't see mentioned in this thread....

finding used stock valves won't work if bigger valves are intended.
most race motors go with stainless and also bigger valves

as mentioned, stainless are available and affordable (in a large variety of sizes)
I've run (used up) 3 different race 2.0/4's with stainless and bigger valves.
never dropped a valve or seat in those 3 motors.
(of course I had a great head builder for them also)

I just bought a set of new sodium valves. Not a big expense - less than the taps and plugs for the oil gallery threading. I bought them because I like the idea of a heat transfer system within a solid valve, and because they use sodium as a coolant in some nuclear subs, and because of the urban legend when I was in chemistry at the University of Washington that someone had tossed half a kilo of sodium metal into the major pond/fountain in front of the building to see the fireworks. If you want dependable maybe a Toyota? A metal that spontaneously catches fire? C'mon, where is the difficult part in this equation?

Just into rebuilding newly acquired 2.0L 914 heads with the 3 stud intake manifold.
I gave the valve heads a few raps with bronze mallet just to see if any were stuck closed prior to pulling valves. One spring suddenly popped up higher.
here's what i found, a fractured stem. Close examination appears to be a brittle fracture with no indications of "beach marks" indicative of progressive fatigue fracture.
See photo.
This would dispel above "stem stretching" as failure warning.
I'll scrap this set of sodium filled valves.
I'm presuming any hollow stem valve is of the sodium filled variety as i have no history on these heads. I'll try to get NEW sodium filled valves, but will go with stainless if can't find hollow stem.
Any good sources for new sodium valves???
Click to view attachment

A lot of the sodum is better crowd info is coming from the 911, it has bigger 9mm sodium valves that work good. I suspect they are a higher quality valve to start with. They do use lower pressure springs because they don't have to push the extra weight of the pushrods and lifters.

Type 4 I'd use new soduim if you can find them, but often I convert the 9mm exhaust valve to a 8mm quality SS unit. Never seen any issues in doing this.

The worst failures I've ever seen have come from Sodium filled, hollow stem valves.

Not for me... And we've had one stainless valve failure in the last 15 years.

Sodium corrodes steel. Only a matter of time.

I agree. Thousands of race miles at high rpm with stainless. Zero problems

I don't think you're going to get a more eloquent and convincing argument against sodium filled valves than this:
.
Usually that's the part of the valve you have to dig out if the shattered piston after the POS came apart at high RPM's. In chunks. I'm sitting here thinking, and can't come up with one good reason to use them. Not one.