OE Exhaust Valves, Sodium Options

[Bleyseng]

My rebuilt rebuilt motor with the new cam is running cooler CHT and oil temps than before. Some of the problems of high temps is a result of the stock cam. Longer exhaust duration means you have cooler temps.

[Demick]

Just a few observations:

1. I have noticed that Jake always is comparing the re-use of an old sodium filled valve to replacing it with a new stainless valve. I think we can all agree that 100K+ mile valves should probably be replaced. The question here should be new sodium vs new stainless.

2. Lots of people trying to correlate valve material to head temperatures. The valve material should have no real effect on head temperatures. The reason for the sodium in the valves was to keep the valve itself cooler - not the head.

Demick

[DNHunt]

I agree that the longer duration probably acounts for the lower head temps. But, that heat has to go somewhere and I can only see 1 place and thats out the tailpipe. I wonder what exhaust gas temps are like. I wish I had that info. Also with the exhaust valve off of the seat more wouldn't the valve soak more heat? I wounder what the steel alloy was in the stock valves and how it absorbed and dissipated heat. If it wasn't as good as SS at dissipating heat that may narrow the difference between SS and sodium filled valves.

Dave

[Demick]

Dave

Very generally, steel has 2-3 times the thermal conductivity of stainless.

Demick

[Bleyseng]

QUOTE (DNHunt @ Apr 3 2006, 08:52 AM)

I agree that the longer duration probably acounts for the lower head temps. But, that heat has to go somewhere and I can only see 1 place and thats out the tailpipe. I wonder what exhaust gas temps are like. I wish I had that info. Also with the exhaust valve off of the seat more wouldn't the valve soak more heat? I wounder what the steel alloy was in the stock valves and how it absorbed and dissipated heat. If it wasn't as good as SS at dissipating heat that may narrow the difference between SS and sodium filled valves. Dave

I don't know what the exhaust temps are but the exhaust sound is different. Blair and I noticed it as soon as we started the bugger up. I think I would rather have the heat go out the tailpipe than into the valve then head.

I thought the sodium was used to transfer the heat outta the valve head into the stem where it could transfer to the valve guides better. (IMG:http://www.914world.com/bbs2/html/emoticons/cool_shades.gif)

[J P Stein]

The sodium transfers heat from the head to the stem of the valve.
The stem transfers the heat to the valve guide & oil......when the guide is excessively worn, this heat transfer starts to break down. Left to it's own devices this does not get better, but worst.....over heating the valve which can burn or just snap off.

[Bleyseng]

and if the valve guide is worn the valve does not seat properly to transfer heat from the head.

So worn valve guides causes all the problems

[alpha434]

QUOTE (Bleyseng @ Apr 3 2006, 11:57 AM)

and if the valve guide is worn the valve does not seat properly to transfer heat from the head. So worn valve guides causes all the problems

No.


Would anyone be willing to try beryllium copper valve guides?

[SLITS]

QUOTE (alpha434 @ Apr 3 2006, 12:39 PM)

QUOTE (Bleyseng @ Apr 3 2006, 11:57 AM) and if the valve guide is worn the valve does not seat properly to transfer heat from the head. So worn valve guides causes all the problems No. Would anyone be willing to try beryllium copper valve guides?

NO

[davep]

QUOTE (Bleyseng @ Apr 3 2006, 10:57 AM)

and if the valve guide is worn the valve does not seat properly to transfer heat from the head. So worn valve guides causes all the problems

Yes, the main problem is with worn guides. For efficient heat transfer you need metal to metal contact with only enough oil to prevent seizing and to fill all the voids. As the guide wears, there is less contact, more oil and sometimes air bubbles. Neither air nor oil conducts heat like metal so the heat transfer goes down and the valve stem temperature goes up. Once guide wear begins the process accelerates.

While guide wear is a big problem it is not the only problem. The state of engine tune and valve adjustment can also play a significant part. So does the amount of cooling air the engine gets. More modern guide materials help a lot, but are not a godsend. To paraphrase Jake, it is all in the combo.

[Matt Meyer]

QUOTE

Jake question for you... you've done alot of work on Aircooled Aircraft Engines.. Lycomings, Continentals, etc... what are those valves spec'ed out as (i.e. sodium filled or solid?)

I'm no Jake but apparently in the application described below Lycomings do, Continentals do not. The makings of a fair case study.

see hereAircraft valve discussion. Go down to "The problem with sodium filled valves."

Sounds familiar huh.

[Bleyseng]

Good food for thought on how fixing one problem leads to other unforseen problems or Murphys's Law.


"The Problem of Sodium Filled Valves

As revealed above, sodium filled valves in the O-320 engine did not eliminate valve distress problems. To the contrary, our question is whether or not they either cause or increase these problems. Sodium filled valves are an extremely expensive component that we believe are greatly to blame for valve/guide distress incidents. They do not make heat magically disappear, as some would have you believe. All these valves do, at great monetary expense, is transfer heat from the valve head to the valve stem, or more generally, from the combustion chamber to the cylinder head via the valve guide. They merely move heat from point "a" to point "b." It still has to be eliminated from the cylinder head by either air cooling or oil cooling or both. The problem is that valve guides are wearing out prematurely and are doing so in spite of operators keeping CHT levels in the proper range. Excess heat is the primary cause of premature guide wear (in a properly assembled cylinder), as most engine shops will tell you. The problem with sodium filled valves is that they serve to import even more heat into the guide by transferring it up from the valve head. Lycoming's long history of valve/guide failure incidents in the parallel valve cylinders has shown that there is simply no way that the guide can shed all of its higher heat load via the cooling fins alone, and Lycoming's design provides for very little oil to aid in that process. The irony here is that Continental uses solid stem valves that dissipate most of their heat into the valve seat. Relatively little comes up the stem and into the valve guide and yet Continental has an abundance of oil in this area to aid in heat transfer. If sodium filled valves are needed at all, one wonders why Continental doesn't use them, since their barrel style hydraulic lifters provide substantial oil for additional cooling of the guide and valve. Lycoming's mushroom style lifters do not. We think that without any change in oil flow to the rocker boxes, Lycoming valve and guide longevity might well benefit from simply going to solid stem valves. Unfortunately, these are not available."

"One of the most vexing problems we had to consider is why some valve/guide failures result from excessive guide wear (the guide inside diameter increases) while others result from valve sticking, which is caused by a buildup of "cooked oil" (coking) on the valve stem. How could insufficient oil volume to the rocker boxes account for both of these seemingly opposite effects? The fact is that we cannot say for certain why one specific failure mode occurs versus another in any given engine. Both, however, are related to excessive amounts of heat in the valve/guide combination. Incidents of valve sticking appear to be greatly reduced now as compared to in the past. All but one of the incidents reported to us involved failures with either disintegrating valves in flight or with the valve's failure to seal during a compression check, caused by excessive guide wear. But we were able to find out how an increased flow of oil to the rocker boxes accounts for lower incidents of both excess wear and sticking.

The answer came in part from our testing and in part from a 50-year old Society of Automotive Engineers report. Our data was showing consistently that the odd numbered cylinders received considerably less oil to the rocker boxes than did those on the other side of the engine and that the odd side had much higher incidents of excessive valve guide wear. Lycoming has repeatedly stated that this distress is caused by excessive valve/guide temperature, although CHT levels in the affected aircraft were normal. We were simply finding that the additional oil to the rocker boxes evidently provides extra valve and guide cooling which is greater than what the cooling fins alone provide. And, not surprisingly, we found that cylinders with this additional oil (the even numbered ones) had generally longer valve and guide life than did those with a lesser amount of oil. But how did this relate to valve sticking problems?

The answer came from an extensive study done by the Society of Automotive Engineers nearly 50 years ago. As Robert V. Kerley of the Ethyl Corporation explained in a paper in SAE Quarterly Transactions, Vol. 1, No. 2 (April 1947): "Practice has indicated that sodium-cooled valves will tend to increase valve-sticking troubles unless lubrication is increased, preferably by an oil jet to the stem, or unless the stem is run dry. "Light or moderate lubrication normally causes coke formation resulting in sticking." (Our emphasis)."




(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

[Twystd1]

Somebody explain to me how an Airplane piston engine that never sees the high side of 2700 RPM (with a few exceptions)

has anything to do with what we are talking about?

And airplane engines are either water cooled or air cooled with more air going across the cylinders and the engine than we can even imagine.

Me thinks you are comparing apples to sherman tanks.

Differant application and very differant enviroments...........

Lousy comaparative analysis.... In my non-humble opinion.

AND:

It doen't matter if it's Jake of Len or Brett or Me for that matter that makes a comment on how it should be or what to use. Don't keep shooting the messenger. It's only data... Biased and/or opinionated or not... It's only data.

And what is needed on a race engine isn't always needed on a street engine. Couldn't agree more.

For me... On any engine that can see 6K easily. any valve that has seen 100K in mileage is tossed. Period.

Too much risk of valve seperation. Cause I spin my engines to redline constantly. To expensive to take a chance.

Sodium or not? I use stainless. With new guides.

What you use doens't matter. cause they all work. Including sodium filled.

To which is better for a street engine.

If I used a Raby cam.. I would go stainless. Cause the head temps are down.
If I was to go with a bone stock cam... I would use either one.. and ONLY if they were new valves.

And I have a spare NOS/OEM set of sodium filled 1.7 or 1.8 (can't remember) valves if ya need em.. I will never use them. Not for free... But for cheap...... (with springs, retainers and keepers, intake and exhaust all NOS)

Clayton

[Brian Mifsud]

".......... yet Continental has an abundance of oil in this area to aid in heat transfer."

Interesting comparison of Apples to Apples which COULD be taken advantage of in a Type IV engine.. enhanced internal plumbing in the head to get oil in and out of the valve stem/seat area. Might take a new casting, but this feature is RPM-Independent.

I don' t think there was any messenger shooting involved. It was a little too tempting to simply accept that more success was found with non-Sodium filled valves without some investigation.

It makes sense to me that valve guide wear (and thus, lack of thermal heat transfer from valve to head) is the MORE important culprit which hadn't occured to me before. Getting more oil in and out of this area, if feasible, also seems like a useful improvement for durability, be it tooling around town, or screaming down the track.

I think this thread has been very helpful.

Thanks

Brian

[Matt Meyer]

QUOTE

Somebody explain to me how an Airplane piston engine that never sees the high side of 2700 RPM (with a few exceptions) has anything to do with what we are talking about?

1st of all let's all agree that Lycoming sodium filled valves should not be used in a Type IV engine. (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)
(You know someone is going to show that Lycoming and Volkswagen valves are nearly identical now)

You asked so:

1) Someone asked if there was any data on sodium filled valves in the aircraft industry.

2) I said it was a good case study because in the aircraft application one company (Lycoming) produced sodium filled valves to cool the valve. The other company (Contentiental) used a solid valve. So we have a comparison between the two designs in similar enviromental conditions to each other.

3) Lycoming appears to have issues with premature failure and premature valve guide wear, Contentiental does not (maybe for reasons unrelated to the valve design). IIRC these are problem areas in the 914 Type IV engine. (Not sarcasim, I have no practical experience in engine building)

4) No one today (except Jake) is doing any R&D work on the Type IV. If we want answers or advancement we are going to have to look to outside sources and see if analogous data can be applied to our little engines.

5)I am pretty sure these O-320 engines are aircooled so they probably have more in common cooling wise with our Type IV than a 996 engine does or anything in a modern automobile. This is a cooling issue, and the aircraft artical makes me believe solely a cooling issue.

So while not directly applicable the aircraft article suggests that sodium filled valves may in practice under certian conditions cause the problems they are designed to fix. Also note This is the result of an investigation by the author into a problem. Lycoming does not appear to agree with his analysis.

Now I never answered the original question of if sodium filled valves were OK in a stock application because I have no practical experience and think better advice (and not too good advice) is contained in this thread. But I will give my opinon now. I would not risk 100,000 mile valves of any design. New sodium filled valves are probably OK in a stock engine if you have adequate head cooling. I think I personally would use new solid valves as they appear to be "safer" and less expensive.

Finally, in the aircraft application the problem seems to be on engines that are used on engines held at a lower constant speed. So do not lug your engine especially on the freeway. Good advise even if I am misapplying it.

[Bleyseng]

I am not sure that type 4 engines need a spray bar onto the guides as the operating photos I have seen show the the valve covers are 1/2 full of oil as it doesn't drain down fast enough thru the tubes.

I guess that on a high rpm engine oil sprayed directly would help provide fresh oil directly onto the guides instead of splash via the valve covers.

I thought the article was fairly right on vs some NASCAR tech stuff.

[Twystd1]

Many spec racing (NASCAR and others) V8 engines use spray bars for cooling the valve springs and splashing the rollor rockers.

The oil transfers the heat away from the springs so they last the race.

With the advent of spray bars,
better alloys like Ti, better heat treating, ceramic coatings and carbon coatings, and the always controversial Cryogenic metal treatment. Broken valve springs are rarely a problem in race engines.

I did the spray bar setup on a type 4 a while back as it had Pauter roller rockers. A couple of dune buggy bretherin had told me this was the way they kept their valve train alive on long races.. (Baja500, etc.)
I think it was Jake or Fat that showed pics of a Type4 spray bar setup on the web... Hey Aaron... you have the link????

I wish I had the coin/time for a full tilt 3 stage drysump and evac system. Then again.... I would have to build a 8K + RPM to need one. That will get ALL the oil exactly where I want it. And in the volumes and pressures the build dictates.
Thats on my list of have to do before I die projects..... (works in a type1 and v8s)

This is really a great thread... Great example as to why I come here... To learn...

THANKS..!!

Clayton

[J P Stein]

Golly.........what Porsche engine has had 2 cam tower spray
bars per side for the last 35 + years? Ain't the latest technology great? (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)

[Bleyseng]

Aren't 911 engines dry sumped? (IMG:http://www.914world.com/bbs2/html/emoticons/dry.gif)

type4 valvetrain is splash lubed, 30's technology which you should be able to remember JP from when you were a kid!


(IMG:http://www.914world.com/bbs2/html/emoticons/mueba.gif)

[Aaron Cox]

QUOTE (Bleyseng @ Apr 3 2006, 06:54 PM)

Aren't 911 engines dry sumped? (IMG:http://www.914world.com/bbs2/html/emoticons/dry.gif) type4 valvetrain is splash lubed, 30's technology which you should be able to remember JP from when you were a kid! (IMG:http://www.914world.com/bbs2/html/emoticons/mueba.gif)

hows that one taste JP? (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)