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Posted by: rdauenhauer Apr 1 2006, 10:04 PM

I know Jake suggests tossing these, but unfortunantly Im rebuilding a set of heads. Id like to keep them stock, but Im more concerned about longevity.
Is there anything that can be done to improve thier function?

Cryo?

Posted by: r_towle Apr 1 2006, 10:10 PM

Im gonna ask a rhetorical question...

Did the original valves last 100k miles?

Will you drive this car more than another 100K miles???

Rich

Posted by: rdauenhauer Apr 1 2006, 10:29 PM

Actually yes! and that IS the hope.

Posted by: Bleyseng Apr 1 2006, 11:51 PM

toss em as they are 30 years old! Buy new ones if you are dying to have sodium exhaust valves.

I would just install SS

Posted by: alpha434 Apr 1 2006, 11:56 PM

QUOTE (Bleyseng @ Apr 1 2006, 10:51 PM)

toss em as they are 30 years old! Buy new ones if you are dying to have sodium exhaust valves. I would just install SS

SS as in Stainless Steel?

Stainless steel conducts heat faster than steel. And the reason sodium filled valves were used was to STOP heat conductivity. Titanium doesn't conduct heat as fast as steel either. But stainless would be a huge downgrade.

Chances are that the ones you have are good. Clean 'em up. Reuse 'em. No problems. Just remember to keep the same valves matched to the same ports on the heads, or to polish them if you're using new heads.

Posted by: Brando Apr 2 2006, 12:16 AM

QUOTE (alpha434 @ Apr 1 2006, 09:56 PM)

QUOTE (Bleyseng @ Apr 1 2006, 10:51 PM) toss em as they are 30 years old! Buy new ones if you are dying to have sodium exhaust valves. I would  just install SS SS as in Stainless Steel? Stainless steel conducts heat faster than steel. And the reason sodium filled valves were used was to STOP heat conductivity. Titanium doesn't conduct heat as fast as steel either. But stainless would be a huge downgrade. Chances are that the ones you have are good. Clean 'em up. Reuse 'em. No problems. Just remember to keep the same valves matched to the same ports on the heads, or to polish them if you're using new heads.

But how quickly does stainles steel dissipate heat to the valve seat, compared to sodium-filled exhaust valves?

From what I've read, Stainless is NOT a good head conductor, and dissipates heat quite rapidly to surrounding conductors. Currently reading up on it's thermal-dynamics.

Posted by: messix Apr 2 2006, 12:20 AM

the valve stems are filled with sodium to isolate the heat to the head of the valve.
you want high heat transfer to the valve seat to keep the valve cool.

Posted by: DNHunt Apr 2 2006, 06:49 AM

QUOTE

Is there anything that can be done to improve thier function?

I can think of 1 thing that helps indirectly at least. Keep the heads cool. Don't lug it. Keep the fins clear and the cooling system in good shape. Keep it timed right. Yada, yada, yada

After following you a couple times forget the lugging comment cause you never go slow enough to lug it.

Aren't I a lot of help.

Dave

Posted by: davep Apr 2 2006, 06:59 AM

QUOTE (alpha434 @ Apr 1 2006, 09:56 PM)

And the reason sodium filled valves were used was to STOP heat conductivity.

Absolute nonsense. The liquified sodium in the valve stem sloshes back and forth to transfer heat faster from the valve head to the stem. Then through the valve guide and into the head. This design is like a heat pipe that is so much in vogue in heat transfer circles today, but does not use two phase operation and instead requires mechanical motion.

Now titanium is a good insulator, and tends to trap the heat in the valve head, comparatively speaking. So this lightness of the Ti valve is offset by its heat transfer characteristics.

Posted by: Bleyseng Apr 2 2006, 08:29 AM

I don't use 30yr old valves in my cars....if you want go ahead. SS valves are much improved over 30 yr ago too and 30yr old valves like to lose their heads.

Posted by: J P Stein Apr 2 2006, 08:48 AM

QUOTE (davep @ Apr 2 2006, 04:59 AM)

Absolute nonsense. The liquified sodium in the valve stem sloshes back and forth to transfer heat faster from the valve head to the stem. Then through the valve guide and into the head. This design is like a heat pipe that is so much in vogue in heat transfer circles today, but does not use two phase operation and instead requires mechanical motion.

This is the internet, Dave......where nonsense passes for fact....you got a problem with that?

Posted by: r_towle Apr 2 2006, 09:10 AM

Here is my logic.

The car/engine was designed for longevity, not super performance...

It was designed by alot of engineers...real automotive engineer, with dynos, testing equipment etc...

the original valves last 30 years, provide 100k+ of service.
They work with the stock motor design.

If I am rebuilding a head, stock motor, stock vavle sizes...I use stock valves, sodium filled.

I would never re-use valves, not worth it.
The top of the valve stem is usually mushroomed, and needs to be re-ground, and re-hardened. not an easy DIY process.

The new valves are 55 bucks ...

I would say, dont re-use, but go with what the orinigal engineers specified for this motor...the same conditions...you will get another 100k plus from the motor.

The original seat material has been upgraded, that was a failure point..so get the seats replaced.

The valve guides are normally beyond service at 100k miles, so you will need to replace those as well.



Rich

Posted by: Rotten Robby Apr 2 2006, 10:54 AM

...and for a fun experiment you can do at home! Cut open the old liquid sodium filled valves and pour that liquid sodium down the sink! Your kids will love it! Your wife... Well, not so much. She will be needing that new kitchen now, thank you!

Actually, I agree. The head rebuilders who do mass quanitity not quality are going to toss them and use new valves that are not sodium filled. They might give you the same arguement about 30 YO technology but what it really boils down to is that $55 per valve. Performance head rebuilders might use something different because they are working with different set of goals. If you don't want to rebuild those heads every few years you probably want to use sodium filled valves...

Posted by: r_towle Apr 2 2006, 10:57 AM

what happens when you pour it down the sink??
smoke?
Fire?

come on...do tell..anything cool??

Rich

Posted by: bd1308 Apr 2 2006, 11:10 AM

QUOTE (r_towle @ Apr 2 2006, 10:57 AM)

what happens when you pour it down the sink?? smoke? Fire? come on...do tell..anything cool?? Rich

My dad had access to his chemistry teacher's closet of stuff. He grabbed a sample of sodium (fist sized) and took it to a local lake....him and a buddy threw it in a lake and it floated down a little bit and he watched in horror as it floated nearby a bridge, and just before it got to the bridge BOOM! and a large column of water surged up from the lake!

if you put potassium (small amount 1/4 dime size) in a coffee pot with water..it'll blow the coffee pot apart.

b

Posted by: J P Stein Apr 2 2006, 11:10 AM

QUOTE (r_towle @ Apr 2 2006, 08:57 AM)

what happens when you pour it down the sink?? smoke? Fire? come on...do tell..anything cool?? Rich

You don't even have to get it wet.....the humidity in the air will set it alight. Nuthin' to fool with.....

Posted by: Rotten Robby Apr 2 2006, 11:13 AM

QUOTE (r_towle @ Apr 2 2006, 08:57 AM)

what happens when you pour it down the sink?? smoke? Fire? come on...do tell..anything cool?? Rich

Oh sorry Rich, Liquid sodium explodes when it contacts water.


Liquid sodium + Water = Boom!

Posted by: Jake Raby Apr 2 2006, 11:59 AM

I can't stand not posting on this topic.

If Stainless valves are horrible I have over 900 engines that are time bombs! Thats because I have not used a Sodium filed valve since around 1994 for ANY APPLICATION!

The Sodium valves were leading edge in the 1970s, today the technology behind the tainless valves is much higher than it was in the 70s. I have had 3 valve failures with stainless valves in the past 7 years, two of which were in full blown race engines, spinning 8,000 RPM and the owner did not complete valve adjustments at my specified intervals. The last one was recent when a customer installed a set of ratio rockers against my recommendations without even checking valve train geometry. It was an intake valve, not an exhaust!

All my personal cars run stainless valves from SI industries along with all my engines. This includes engines in my "Super Hero" line up, even the Mighty Spyder! Not all stainless valves are created equal, some are pure junk, while the SI valve is incredibly strong and light and can take the abuse of a full bown race engine.

For someone to recommend a used sodium filled valve over a brand new Stainless version is pure stupidity and shows one thing: lack of experience! I had to read that one 3 times and I still didn't believe it- pure bullshit!

Thats because experience teaches us at teardown what fails and if you had seen as many engines blown to bits BECAUSE OF SODIUM VALVES as we have you certainly would not make this statement. Have one failure due to Sodiums and you won't say it, see a few dozen more and you'll be about as experiebced with it as we are.

When a Sodium valve goes without adjustement, or when it gets ready to let go the valve explodes and blows the piston and even the cylinder to bits! I have had this happen on my 914 engines when it was stock and nothing could be reused- not even the case, or the crank or even the rods! I have seen this many times and even more severe. I posted the pics of the failure in 2002 and most people swore the engine was turning 8K, nope a chick was driving it!

The other issue with Sodium valves is that they are only made in 9mm stemmed versions that weigh about 17 grams more than our stainless steel version and 17 grams of valve mass is worth it's weight in gold for valve control.

So there ya have it, the view that experience has taught me about Sodium valves. We do not use Stainless valves because they are cheaper, we use them because they are BETTER- period. Racer Chris turns his 8,500 RPM for a full season with no sweat at all in a 186HP 1832cc engine, that should speak volumes.

Okay, back behind the curtain, I just had to stop the Bullshit that was starting to get deep in this thread!

BTW- if you don't agree with me, then



Hey, maybe someone should go chuck up a Sodium valve in a valve grinder and see what happens. Alpha, wanna go try it?? You'll be geting out of the hospital about the time I come back to the forums, I would hate for you to miss my posts-

Posted by: Aaron Cox Apr 2 2006, 12:05 PM

Posted by: r_towle Apr 2 2006, 12:20 PM

QUOTE (rdauenhauer @ Apr 1 2006, 11:04 PM)

I know Jake suggests tossing these, but unfortunantly Im rebuilding a set of heads. Id like to keep them stock, but Im more concerned about longevity. Is there anything that can be done to improve thier function? Cryo?

I believe STOCK is the operative word here.

Again,,,designed to provide longevity..not turn at 8500 rpms...

As far as owned goes...well whatever...I personally like the free flow of information that people have on these types of forums...I think everyone here has lost some balls...no one speaks up anymore for fear of getting bullied...

I dont like bullies,

Rich

Posted by: J P Stein Apr 2 2006, 12:28 PM

Viturally all OEM manufactures of high performance engines
use sodium filled ex valves in their engines.

That the T-4 valve design is deficient (per Jake) is tough nuggies.....but it's hard to argue that point if folks are gettin' 100 K miles out of them.

I'll piss off now & get to work on my car....sodium ex valves & all.

Posted by: Bleyseng Apr 2 2006, 12:35 PM

Very few VW engines came with sodium exhaust valves stock and it really was a 70's trick to control the higher exhaust temps due to the crappy hot running cams they were running.

Modern valves are way stronger and thats why I use them even in my stockish motors.

Jake has strong opinions thats true but that never stops me from posting my opinion.

I have been playing with VW motors since the late 60's and they have come along way since then in some respects. Tons of cheap quality stock parts from VW is one thing that isn't around nowdays.


this is getting funny! Rich, you are a troublemaker!

Posted by: newto914s Apr 2 2006, 12:45 PM

I had my heads rebuilt at EMC in LA, and they advised me against going with Stainless valves. For heat reasons related to running unleaded pump gas, putting around town. They ended up putting in SI stainless, basically because I couldn't afford the stock valves. Now my heads are running hot, 375+ at times. Their are a lot of variables still left to sort out which may explain the heat. But I am alittle concerned that I may never be able to get it under control now.

Posted by: MarkV Apr 2 2006, 12:49 PM

I have a set w/ 5,000 miles on them that I will sell cheap. Like $20 each.

I had Len Hoffman rebuild my cracked heads & he recommended stainless so I replaced them. He said they looked new & had no wear on them.

Posted by: Jake Raby Apr 2 2006, 12:51 PM

I was simply making opinions based on my experience, thats something you can't find just anywhere in vast numbers. Most everyone who has posted here on the subject is basing their opinions on thoughts made by someone else that they may have read, or what a new engine manufacturer may be doing. The advice I offer is NOT based on this and many times it defys it, and causes controversy- thats to be expected.

The newcars being made with Sodium valves are NOT air cooled-

At any rate I'm not trying to be a bully at all. I simply can't believe that anyone would recommend using a 100K mile + sodium filled valve over a new Stainless valve. Hell, who knows the state of that used valve??

I offer the reader real facts and it's up to the reader to choose to listen or not. If they do they'll be benefitting from real experiences that may save them the bullshit that Brent and I have had to break things to learn..
So' I'm not trying to be a bully- I'm trying to share my particular experience with this particular engine, which IS vastly different in many aspects than anything else you'll read about.

QUOTE

Now my heads are running hot, 375+ at times. Their are a lot of variables still left to sort out which may explain the heat. But I am alittle concerned that I may never be able to get it under control now

OK, now think about this one..

If Stainless valves run hotter and do not transfer heat into the seats (as claimed here by the experts) wouldn' your heads be running COOLER because the valve isn't transferring it's heat to the seat and then into the valve??

Your temperature issues are configuration and or tuning related or both- Not the material of your valves! My 2270 runs head temps lower than 300F all the time and it's 170 ponies. (But it's configured correctly and tuned correctly :-)

Posted by: r_towle Apr 2 2006, 12:53 PM

I miss something here...

I am just pointing out that human nature is to question, try new things, look at new ideas, make mistakes, learn from those mistakes.

I appreciate what a hard earned reputation Jake has earned. His work speaks for itself in the community that can afford to buy his products and services.

What this forum represents is a place for 914 owners/wanna be owners/ ex-owners etc to have an open discussion on things we have tried, want to try. etc...

When a particular topic comes up, always the same thing happens, and again, I am not argueing at all in the knowledge..just the delivery.

These motors are older than me, have been being rebuilt since before my time, and have been being raced since before my time...so there is knowledge out there...and it comes from more than one place...

Put yourself in an open room, full of people...everytime a conversation comes up there is not just one opinion, and when other people have an opinion or an idea,,,we would all listen, give our experiences and the conversation stays civil and moves along naturally...

That is not happening anymore..
I am trying to be as polite as possible here...but I know I am not alone also.

Please, other people have brains, other people have ideas. Alot of the creative responses that used to be here are all gone, there is fear of being publicly humiliated on our own forum...WTF

Controlling a conversation is what sales is all about...
I know.

But open exchange of ideas and information is what a forum is all about.
For me to keep hearing...dont think, buy this...
Well, I like to think....

I got into these cars in the first place over 30 years ago because they are simple and cheap..
Two very important point, SIMPLE...and CHEAP...

Not rocket science and platinum expensive..

If I wanted to spend 30k and get 400hp I would buy a toyota supra...lots of cool goodies, new computers etc...

What I like is that these cars attract the cheap guys and we all share how to do it cheap...
Same as the 356 guys used to be.

Again, I am encouraging free information exchange, not a single opinion, though valued, is not always the answer...

If a guy needs to put a motor together used,,with all used parts,,tell us how you did it...not how you would do it with 5k in extra cash laying around...

Think about it...it can be done...it has been done...but no one has the balls to talk about it anymore...

And please, dont storm out of the room and slam the door...

Rich

Posted by: alpha434 Apr 2 2006, 12:53 PM

Hey Jake!

We've got a submerged grinder just for that kind of task.
Were there is a will, there is always a way. Especially in machining. You know that. There is no need to suggest that any good machinist would be hurt, because there is always a safe alternative.

Guys used to machine beryllium submerged. Thought it was no big deal.

QUOTE

I appreciate what a hard earned reputation Jake has earned. His work speaks for itself in the community that can afford to buy his products and services.

Agreed. Jake is THE name in type IV performance.

QUOTE

What I like is that these cars attract the cheap guys and we all share how to do it cheap... Same as the 356 guys used to be.

This stopped when "the only way to be" in 356land was to buy a 5000$ engine.

QUOTE

Please, other people have brains, other people have ideas. Alot of the creative responses that used to be here are all gone, there is fear of being publicly humiliated on our own forum...WTF

Huh?

Posted by: Mueller Apr 2 2006, 01:27 PM

QUOTE (J P Stein @ Apr 2 2006, 11:28 AM)

Viturally all OEM manufactures of high performance engines use sodium filled ex valves in their engines.

yep, the new 2006 500+ horsepower Z06 Vette uses sodium filled exhaust valves....not too bad for a $20K motor...

I see no reason that you cannot run Brand New sodium valves and not suffer any drama....

Posted by: Bleyseng Apr 2 2006, 02:19 PM

QUOTE (rdauenhauer @ Apr 1 2006, 08:04 PM)

I know Jake suggests tossing these, but unfortunantly Im rebuilding a set of heads. Id like to keep them stock, but Im more concerned about longevity. Is there anything that can be done to improve thier function? Cryo?

Ok, anybody cryo'd these fancy sodium filled valves??


order some SI ss valves Rich and get a 9550 cam so you runit cooler.

Posted by: rdauenhauer Apr 2 2006, 04:17 PM

QUOTE

this is getting funny! Rich, you are a troublemaker!

I aim to please

he he he better than 14 threads about which oil to run or how much hp can be made

QUOTE

Ok, anybody cryo'd these fancy sodium filled valves??

thanks for bringing this back to the original Q, Geoff

So if Cryo is supposed to "tighten up" the molecular structure of the metal why couldnt you treat evan 30 yr old albeit GOOD condition S. Valves and reuse?

Posted by: jsteele22 Apr 2 2006, 05:13 PM

Interesting thread, had no idea it was gonna be so contentious. I've got no opinion one way or the other, but I thought I'd add a few things to the mix.

The issue with exhaust valves is not getting them too hot. Filling them w/ sodium, as was mentioned well down in this thread, is to make the valve a good conductor of heat. You want the heat to flow from the head of the valve where temperatures are highest down the stem to where it can be conducted out of the valve. Not only is sodium a good conductor, but (as mentioned) it melts at really low temperatures, so there is also some convection going on.

Stainless steel, by comparison, is a fairly crappy conductor of heat. I'm guessing that what has changed over lo these many decades is that good SS valves strike a happy balance between having slightly better thermal conductivity and also being able to survive higher temps.

So what's the big deal with sodium exploding ? Simply put, it combines with water (H2O) and grabs the OH, releasing the H (hydrogen) in the form of a gas. This process is exothermic, meaning it also releases a fair amount of heat. So if you combine sodium, water and air, you might get an explosion. If you want an explosion, use lots of sodium in a small amount of water. Actually, the reaction is so fast, that a smallish chunk of sodium will skitter around on the surface of a pond due to all the hydrogen gas streaming out. Kind of like a mosquito having a fart attack. If you don't want an explosion keep the sodium away from water or air or both. If you read in the manuals of cars that have sodium filled valves, you might be suprised to find the recommended means of disposing of them : grind through the valve until you hit the sodium, then drop it into a bucket of water ! Is this crazy ? Not really. The amount of sodium is small and the valves are heavy. They sink to the bottom, the water reacts with the sodium until its all gone, and the hydrogen bubbles out to the top of the water, cooling off very rapidly. Unless you intentionally try to ignite it, it will just diffuse out into the air.

Carry on.

Posted by: bd1308 Apr 2 2006, 05:20 PM

sounds like sodium could be used to make hydrogen for fuel cells?

b

Posted by: alpha434 Apr 2 2006, 06:00 PM

I'm not sure if you could cryo sodium filled valves. The different expansion rates between the sodium and the steel might cause the valve to shatter during the freezing process.

Just my thoughts, still definately worth a try!

Posted by: davep Apr 2 2006, 06:01 PM

QUOTE (J P Stein @ Apr 2 2006, 06:48 AM)

This is the internet, Dave......where nonsense passes for fact....you got a problem with that?

Yep, I sure do have a problem with that.
I know a teensy bit about 914's, gathered since 1975. I hate to see anyone make a decision based on .
Jake has a lot of experience that even the factory engineers didn't have. He also has had a few years to figure out solutions with materials not even thought about during the design years. But hey, nobody is perfect, especially not me.

Posted by: Al Meredith Apr 2 2006, 06:57 PM

Sodium is used in LOW PRESSURE SODIUM LIGHT BULBS. You guys in San Diago and Phoenix know about those monochromatic Yellow street lights. Break one of those in H20 and get back. In WW2 airplane engines used Sodium valves. What do aircraft engines use today??

Posted by: alpha434 Apr 2 2006, 07:05 PM

QUOTE (Al Meredith @ Apr 2 2006, 05:57 PM)

Sodium is used in LOW PRESSURE SODIUM LIGHT BULBS. You guys in San Diago and Phoenix know about those monochromatic Yellow street lights. Break one of those in H20 and get back. In WW2 airplane engines used Sodium valves. What do aircraft engines use today??

Didn't most of the successful WWII airplanes use sleeve valves, not popett valves?

And now, don't most of the successful airplanes use jet engines, not recriprocating engines?


BUT, jets do use SS in certain places. But it's an aircraft grade 8000 series stainless, used for hardness (80+Rw.)

That material is too brittle for our applications, it's expensive and not readily available. I've got a huge chunk of it that I got from Ball. And the thermal properties suck.

Posted by: DNHunt Apr 3 2006, 07:58 AM

I'm not sure if this helps or not. I've run 2 engines in my car with the same CHT, thermocouple and ring under spark plug #3. It has the same drive train including wheels and tires. The old engine was a 2056 with stock heads and sodium filled exhaust valves. The customary head temp on the freeway at cruise (3200 rpms) was 310. The new engine is a 2270 with heads supplied by HAM thru Jake and have SS exhaust valves. Plenty of stuff is different inside the engine so it's not a perfect test but these heads run at 290. Maybe the SS valves retain more heat or maybe it is the combo as Jake says but, the heads are definately cooler.

Dave

Posted by: Brian Mifsud Apr 3 2006, 08:39 AM

Just to put some FACT into this world of FICTION:

Sodium Melting Temperature 371Kelvin = 208 Fahrenheit (Nuclear Power Plants use this to cool the reactor)

Heat Transfer Coefficient 1026 - 1038 J/Kg*K


Stainless Steel Heat Transfer Coefficient 460-480 J/Kg*K

To prevent "head spinning", this means 1 unit of sodium will
conduct heat almost 3 times better than 1 unit of Stainless Steel.

Jake may be witnessing more failures with Sodium filled valves,
but that may more to do with the fact that the valves are hollow to allow Sodium
to be injected, thus having a smaller/weaker cross section. More an issue on
engines at the higher RPM range of course.

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?)

My ASSUMPTION is that "airworthiness" is a measurement of reliability???

Posted by: maf914 Apr 3 2006, 08:58 AM

QUOTE (DNHunt @ Apr 3 2006, 05:58 AM)

The new engine is a 2270 with heads supplied by HAM thru Jake and have SS exhaust valves. Plenty of stuff is different inside the engine so it's not a perfect test but these heads run at 290. Maybe the SS valves retain more heat or maybe it is the combo as Jake says but, the heads are definately cooler. Dave

Dave, Don't you also have a set of Nickies in that combo? They transfer heat at a much greater rate than the stock cast iron cylinders. I wonder what effect they have on head temperature?

Posted by: DNHunt Apr 3 2006, 09:11 AM

QUOTE

Dave, Don't you also have a set of Nickies in that combo?

Very true. There is no way to make a really good comparison. One other observation, oil temps are higher. My guess is that it takes the same amount of work to move the car and therefore, the amount of heat released must be pretty near the same. It just goes elsewhere.

Dave

Posted by: Bleyseng Apr 3 2006, 10:19 AM

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.

Posted by: Demick Apr 3 2006, 10:30 AM

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

Posted by: DNHunt Apr 3 2006, 10:52 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

Posted by: Demick Apr 3 2006, 11:07 AM

Dave

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

Demick

Posted by: Bleyseng Apr 3 2006, 11:10 AM

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.

Posted by: J P Stein Apr 3 2006, 12:43 PM

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.

Posted by: Bleyseng Apr 3 2006, 12:57 PM

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

Posted by: alpha434 Apr 3 2006, 01:39 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?

Posted by: SLITS Apr 3 2006, 02:01 PM

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

Posted by: davep Apr 3 2006, 02:06 PM

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.

Posted by: Matt Meyer Apr 3 2006, 02:22 PM

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 herehttp://egaa.home.mindspring.com/engine3.htm. Go down to "The problem with sodium filled valves."

Sounds familiar huh.

Posted by: Bleyseng Apr 3 2006, 02:46 PM

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)."

Posted by: Twystd1 Apr 3 2006, 02:58 PM

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

Posted by: Brian Mifsud Apr 3 2006, 03:15 PM

".......... 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

Posted by: Matt Meyer Apr 3 2006, 04:06 PM

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.
(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.

Posted by: Bleyseng Apr 3 2006, 05:29 PM

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.

Posted by: Twystd1 Apr 3 2006, 06:03 PM

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

Posted by: J P Stein Apr 3 2006, 07:33 PM

Golly.........what Porsche engine has had 2 cam tower spray
bars per side for the last 35 + years? Ain't the latest technology great?

Posted by: Bleyseng Apr 3 2006, 07:54 PM

Aren't 911 engines dry sumped?

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

Posted by: Aaron Cox Apr 3 2006, 08:07 PM

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

Aren't 911 engines dry sumped? type4 valvetrain is splash lubed, 30's technology which you should be able to remember JP from when you were a kid!

hows that one taste JP?

Posted by: TimT Apr 3 2006, 08:22 PM

QUOTE

Aren't 911 engines dry sumped?

yeap 911s are dry sumped... which has EXACTLY zero to do with cam/valve lubrication/cooling

funny thing.. all this talk about stainless steel vs sodium filled valves..

FWIW many thousands of 911 engines are out there as we type with sodium filled exhaust valves. Been running really high output air cooled engines for years.. and have never had an exhaust valve failure...

My 800+ hp turbo engine has sodium valves, and spins to 9000rpm.

I only replace valves when they dont measure to spec..

I think our 996GT3RS engine has sodium filled valves..Ill check soon

Posted by: DNHunt Apr 3 2006, 08:34 PM

Damn that was good

Dave

Posted by: J P Stein Apr 3 2006, 09:38 PM

30's technology?
I'm 40's technology.....and my taste in engines has improved since then.

Posted by: sixnotfour Apr 3 2006, 11:03 PM

935 oil cooled/lubed guide exhaust,oil cooled/lubed spring seat intake.
(welding rod shows oil path exhaust guide ,groove in flat surface passage to spring seat)

sodium valves 911 yup ,missed shift bends em / bad guides the heads come off, ask eddie914


Attached image(s)

Posted by: sixnotfour Apr 3 2006, 11:07 PM

sideshot


Attached image(s)

Posted by: Mueller Apr 4 2006, 10:31 AM

QUOTE (sixnotfour @ Apr 3 2006, 10:03 PM)

sodium valves 911 yup ,missed shift bends em / bad guides the heads come off, ask eddie914

sorry, but SS or even Ti valves could have done the same thing......"something" is going to let go with a missed shift

Posted by: arc914 Apr 17 2006, 11:52 PM

QUOTE(Twystd1 @ Apr 3 2006, 12:58 PM)

Posted by: arc914 Apr 18 2006, 12:09 AM

Well don't i feel like a beginner. I think i am just as on the fence about SS valves or Sod filled.I still do not know which to buy.
There was alot of great info in this thread and i learned alot about alot-Thanks
but in the end i am on the fence.
the one thing that i do know for sure is that guides are the ket to longevity.
so all new guides is a must.
Does anyone in the thread have a NOS of guides and exhaust valves for sale for me?

Thanks again to all and there twocents
andrew