Sodium Valves ... curious to know

I'm curious to know what the problem is with sodium valves on a 308? I think I know that they're a problem because I seen them mentioned in numerous threads, but please explain to me why they are a problem, and what one can expect to happen as a result of having sodium valves. Sorry if this has been discussed a thousand times.

 

also what years were the valves in, I heard that the qv don't

 

Sodium filled exhaust valves are not a problem, except that the heads break off the stems at the most unappropriate times. Like when the engine is running and they beat themselves to death on top of the pistons! Nothing like a quarter size piece of metal floating around a combustion chamber at 7,500 RPM.

 

I found this thread by the same name: http://www.ferrarichat.com/forum/showthread.php?t=150356&highlight=sodium

2 Vs only. 75 -82, yes?

Interestingly, I did a search in the 308/328 section and there isnt as much discussion as I thought. However, I've seen a drawing / illustration / animation somewhere of how the sodium valves break at the heads. Maybe its in the discussions in the dino section?

James in Denver

 

General opinions are they become a problem w/age...say 60K or so on the motor. I have a 2V and it is a concern but it's not something I have any control over. It is said you can "drive around" it by not maxing out rpms too often. And the power starts to drop off at about 6K anyway so no point in getting caught up in the whole paranoid thing. If I hear a big BANG I'll shut her down and get it towed. Then it's time to pull the motor, port and polish, replace all of the exhaust valves [the only ones that are sodium] and hope no pistons are damaged.

In the meantime I am not loosing sleep over it. It doesn't happen that often and if it did you would here A LOT of stuff on here w/first hand experiences.

I went thru this when I re-built my 2L 914 motor...I used sodium valves due to the fact it's an air cooled motor and it wasn't a big issue there either. FYI the 2V's also used it due to the air system configuration and emmisions..i.e. cooler air introduced in the system along with the sodium valves. So the story goes.

And QVs don't have them

 

Based on TMobileGuy's 348 experience when he lost the belt which caused the valves to clash with the pistons, it wont be a "bang". It will be most likely a smaller noise like pop, then your engine will sound like "a card stuck in the spokes of a bicycle" (in TMobileGuys words) then your engine will quit.

James in Denver

 

Different situation...when a sodium valve breaks it EXPLODES! It is actually hollow and the sodium turns into a liquid state when they heat up [as I understand it] thereby cooling them.

 

When I owned a 246 GT decades ago I bought it from a guy who had broken a sodium-cooled exhaust valve while overreving at a club track event. He actually drove it 100 miles to his home and then drove it to a repair shop. When he learned to cost to overhaul the engine he sold it to me (cheap). When I disasasembled the engine I found that the valve head was embedded in the top of the piston. It had "dented" the head and scraped the cylinder wall. I rebuilt the engine with new pistons, a slight overbore, new valves, and a weld repair on the head. The result was a very reliable (and strong) engine. Dropping that valve head was far less damaging than a broken timing belt at speed. (The 246 has a chain but there have been thread discussions on belt breaking of 3X8s). The valve break was a classic failure of the weld between the stem and the head.

 

I know there is a difference between breaking the belt (and all valves hit pistons, at least the ones that are in an open position) and just one (or 2?) sodium valves breaking, but I didnt think it was an "explosion" as such.

Seems to me that the drawing/illustration that I saw of this potential failure was exactly that, the stem separating from the head. Surprising that someone would WANT to run an engine after this, but I guess it could run as long as the head didnt get stuck elsewhere causing something else to jam.

Robbie, what exactly was the sound and symptoms when it happened?

James in Denver

 

http://www.pless.com.au/cars/gt4/rebuild/images/DSCN0482.JPG
http://www.pless.com.au/cars/gt4/rebuild/images/DSCN0479.JPG
http://www.pless.com.au/cars/gt4/rebuild/images/DSCN0478.JPG
http://www.pless.com.au/cars/gt4/rebuild/images/DSCN0477.JPG
http://www.pless.com.au/cars/gt4/rebuild/images/DSCN0475.JPG

it can happen at any time. some cars did it during pre-delivery!

i've also heard of a car with 200,000m with sodium valves still in it.

when i bought my GT4 last year, i couldn't change the valves fast enough.

 

A search of the archives on this topic will give all kinds of scenarios regarding S.V. failures. Failures at start-up, idle, accel, decel, high RPM's, etc.... The bottom line is that they are a liability in the 308 motor and should be changed out before they break. They happen more frequently than people realize. The PO of Robbies car got lucky, many have had to completely rebuild heads or worse, find a new head, install new cyl. liners, etc. This all = BIG BUCKS!!!! The cost of doing the heads preventively is far less than rebuilding the motor if one goes during flight. I'm doing mine this fall. My fear is that one goes between now and then. It's a risk, but that's my timeframe for doing the motor...

FWIW, YMMV!~
JIM

 

While doing a valve adjustment on my GT4 rebuild one of the sodium filled valves broke! The head litterally snaped off while putting a shim in. I'm glad it happened on the bench and not the first time I drove. Needless to say we replaced them all with "regular" solid valves. I'm glad I did...

 

Interestingly enough, I searched just the 308/328 section with the search word "sodium" and didnt turn up as much as I thought, 45 hits and only 1 or 2 useful threads.

I did not search the old FChat though. Maybe more info there.

James in Denver

 

Not to pick nits, but a lot of this is not really correct. First of all, no one is going to drive around the problem, they can (and have) fail at any speed, even at idle. Second, maybe YOUR engine falls off at 6K, but it shouldnt if its running well. My carb cars dont even max out the ignition advance until 6800, with peak power rated at 7000, and it will still climb decently past that. Third, by the time you hear a BANG, (which in all likelyhood youll be lucky to hear anything) you will be looking at an amazing sum of damage and expense. In your 2V 308 youlll spend upwards of $15K today, perhaps closer to $20K, for a standard overhaul without repairs. The potential exists to do massive head damage as well as a slight risk to damaging the block, crank, rods, it can get ugly.

As to it not happening often and/or people on here happily discussing it if it was an issue, again, not very likely. You see, most of the people on here, myself included, dont want to buy cars that had previous major engine damage, and everyone here knows it. And very few are going to discuss the bad things that happen because they dont want the black mark on the car. The few that have are very brave souls indeed, and we should all give them a proud pat on the back, but they are very rare individuals. So the simple truth is that dropping a valve, blowing a timing belt, etc, are things that we are just never going to see happening in any great manner except by those few individuals who actually turn wrenches on them for a living. And having mentioned that, thier opinion is that it happens much more often than the armchair quarterbacks around here who've never seen the insides on an engine try to speculate. Norwood, Rutlands, Dave Helms, Brian Crall, etc., etc., they are not all lying to us, my friend, they are in fact trying (in vain) very hard to get people to try to save whats left.

As to the 914/VW motors, ive seen so darn many with valve stems shoved through the piston after the head fell off its not even funny. A guy up here that ran a Dune Buggy shop for many decades had semi trailers full of engines and parts, hundreds and hundreds, it was a facinating collection of junque. But I seen enough, and knew enough people who dropped a valve, including myself, that to say its a rare occurence would be of great disservice.

With all this said, I wouldnt worry about until you do an engine out major service, because by the time you get the heads off and start the while your in theres, its going to a major undertaking.

 

From Verell...

There's even less reliable data on the things that can cause a sodium valve to fail than there is on timing belt failures.

Every once in awhile, someone drops one, often associated with an over-rev for whatever reason.

Unlike changing belts, I don't think I remember any of the Pros recommending going in to just to replace the valves as preventive maintenance. The message I've heard is "If you've got to pull a head, change those overly fragile sodium filled valves".

And from Artvonne...

So with a wink of an eye toward Maranello, I am going to do a full engine out service. While its out I plan to seperate the engine and gearbox, pull the heads, replace all gaskets and seals, check bearings and valves, and if God is with me, I plan to replace the exhaust valves with SS. While I'm in there, I hope to do some port matching and possibly up the CR.

The valve dropping issue has fallen off quite a bit over the years. My feelings are that most of the ones that dropped were probably flawed, and the ones that were prone to break broke early in life. Many of the other cars have already been upgraded. As Verell pointed out, there is not a lot of data. IMHO, most owners dont want a record of thier car doing it, so its not discussed or documented, but just quiestly repaired and then forgotten. Remember, if the motor drops a valve, it will do signifcant damage to the head that will require extensive welding to repair, at the very least. And people like me dont want welded heads on our car if we can help it.

Back to Verell...

If you're loosing a lot of sleep worrying about your 2V's sodium filled valves, AND can afford to invest the time or money, THEN pull the heads & replace the valves. At that point the cost of port matching the intake runners & headers with the head ports is a trivial increase in cost. Of course, once you've done changed out the valves, You'll probably start loosing sleep worrying about something else happening to the car.

 

I was speaking to a cylinder head rebuilder about this last week and his take on it was." Of all the sodium filled valves he had seen fail (not just in Ferrari) the main cause was lack of use. The sodium eats away at the valve and causes the failure. He found vehicles that where used often had fewer failurers than vehicles that sat for long periods. May have something to do with heat cycling of the sodium.

 

Sodium filled exhaust valves were an issue on the 246 engine. Even in this case only a batch was defective but this was sufficient to get people worried.
I agreed that 246 engines should have their valves replaced as a precaution but on the 308 this is a non-issue.
If you are rebuilding your engine replacing valves is a small cost and should be part of your rebuilt as you would be replacing guides and seats at the same time.

 

Sodium filled valves are frequently used in large truck engines, and work thusly: when the sodium reaches a high temperature, it liquefies. This liquid sodium splashes up and down in the valve, transferring heat from the head to the stem, thus moving the heat out of the valve and into the cooling system via the valve guides.

Shiny Side Up!
Bill

 

This is always an interesting thread when it comes up. I guess it comes down to risk tolerance....
What is the lesser of 2 Evils...a dropped valve or some preventive maintenance. I'm keeping my car for a while, so I know the answer for myself...

JIM

 

Agreed. I have never heard so much fuss over sodium-filled valves as here with Ferraris. I considered buying a Maserati Merak instead of a 308. They also have sodium-filled Exhaust valves. The word with Meraks has for many years been exactly what you said: it is only a concern on cars that don't get used or have sat dormant for a long time. Lotus Turbo Esprits have sodium-filled valves, too, and it is no more an issue with them.

 

This is a little over the top.... if I already had my heads off, or were in there for some reason, I would probably change them out - otherwise I can't see giving a lick of worry to this.

This statement, by the by, is something I have to respectfully disagree with.. "In your 2V 308 youlll spend upwards of $15K today, perhaps closer to $20K, for a standard overhaul without repairs." I need some of your crack man...

JC

 

Well if you consider that head gaskets are $800 you can see how the price of a rebuild will quickly climb to $15-$20K!

When my valve broke I had to buy new head gaskets to replace the brand new ones I just put in! Again I'm glad it happened on the bench or else I'd have spent money on a rebuild twice...bottom line, if the engine is out don't cheap out for a few hundred dollars...change them!

 

James C -- I think the $15k-$20k is for people who pay someone else to do it. I would expect the DIY price to be somewhere between $5k-$10k, depending on what you replace.

 

I guess I've been a DIY'er for too long..! I sooner chop both my arms off before I paid someone $20K to rebuild my engine. Yikes!!