Sodium valves on 308

I have been thinking of replacing the stock sodium valves with stainless steel.
There were many conversations on this board about them but still kind of confused. Many horror stories and many members have indicated that sodium valves are ok.
Any advise will be greatly appreciated. No catalytic converters on the car!!

 

I have heard of the problems too, but mine have lasted 100,000 miles and are still going strong. If I rebuilt mine today and drive it the same that would mean they would last me another 20+ years.

 

My take on it is that they made a LOT of 308s with sodium valves. They do occasionally break and make a mess. Considering how many are out there, this is clearly not a crisis situation if you have a 2 valve 308. However, were I about to embark upon an engine out service, I would replace the valves while I was at it. I would not consider the valves alone to be reason to tear down the top end.

Birdman

 

The sodium filled valves have the big advantage of heat transfer, but have the problem of "two piece" made format. That is, the bottom of valve is made separated of steam, and it´s increase the risk of valve rupture at high revs(above 8.000rpm).

The aftermarket "one piece" race valves, have badder heat transfer, but is much more stronger for run at very high revs. You pay the price for don´t have sodium filled valves, using more retarded ignition timming or/and colder spark plugs, for prevent detonation(the chambers will work hotter without sodium filled valves).


Cheers,


Matheus S. Almeida

 

I have no issues with the top end.. Out of fear I was was going to tear down the top end to change them.
If Tom's engine lasted that long with out a problem than it makes sence in my opinion to leave them alone.
Thanks for the input.
Tommy A

 

Matheus actually has it right.......thanks!

The older valves were the best they had, but failure is usually due to the two piece construction, I think...and age.

I still run the originals but feel they are even more exposure than the legendary belts...I'd change them all first chance I had......

Also I think if the air injection has "broken' then the air temps at the exhaust are reduced........

New stainless or sodium would allow easy sleeping....and revving!

 

It is my understanding as well that the air injection dramatically increases operating temps on the exhaust valves and header. Having the air injection "fail" makes life much easier on the valves, and then the stainless replacements do not require the extreme heat-shedding qualities of sodium valves.

Birdman

 

If all the polution controls are removed including the air injection,
does anybody see the need to replace the sodium valves?

 

I'll let the more experienced engine techs respond to that.....but these cars are getting pretty old..

I think the wisdom is 'if you ever hold one loose in your hand, throw it away and get a new one.'

To run them to failure you risk the valve bits damaging pistons, sleeves and block........

 

I think the problem is not only the air injection(or EGR system), and yes the rev operation like i said.

If you rev it up always..working above 8.000rpm continuos.. you increase the risk of valve rupture when is sodium filled(two piece made format).

My 4 cyl 16V engine uses sodium exhaust valves, but my rev limiter was set on 8.200rpm, because i have friends that was run 8.500rpm with this valves, and they was broken(the base got separated of steam).

If you don´t put the rev up continuos.. the standard old sodium valves will do the work.

If you have a modified engine or a standard engine that you rev it up with frequency, is time for go to "one piece" race valves.

With or without polution control.


Cheers,


Matheus S. Ameida

 

We have a normal redline of 7,800........I have seen my engine go right on up to 10,500 on a missed shift....no limiters here! LOL!

 

lol!!

Do you have certain that your engine don´t have rev limiter? What is your car ?

Rev limiter is very very important!

10K rpm on two piece valves is not a good thing to do.. lol..

 

Sorry to put a downer on this but

I replaced mine at 73000 miles, one valve had a hairline crack where valve met stem, all other were fine.

A friend of mine replaced his at 21,000 miles 4 years ago, he dropped a valve on the ground from waist height by accident while rebuilding and the valve head cracked off.

Mileage does not seem to be the issue age appears to have more to do with them becoming brittle, or perhaps just totally inconsistent quality standards in Ferrari in the late 70's.

So while it is rare it does happen. All I can say is I was glad I replaced mine, but I was doing a complete top and bottom end rebuild.

 

Thanks Tom.....

There's a real world observation.

Who knows what evil stress cracks lurk, in the heart of a vintage engine..

I only missed that one shift...I'm MUCH more careful now...it was at night and you could see all the glowing carbon flakes blown off and out of the engine.....

If only the heads were'nt such a PITA...it takes huge amounts of work to get them off! Usually stuck in place.....

 

Good info!


I think the future, will be Iconel valves.. the problem is the cost of this special material(all valves of F1 race engines are made from this).

At the moment, i machining Titanium one piece valves for me. Is 35% lighter than steel(it´s mean that you can use lower spring valves rate or keep the same and can run higher rev without valve floating..less inertia..) and have the same resistance of forged 4340 steel.



Cheers,



Matheus S. Almeida

 

My very expensive experience - no air pumps, btw, and less than 40,000km (not miles) on the clock - an exhaust valve came apart and went through the top of the piston, which destroyed itself and then the conrod tore out the liner and then damaged the block and then metal and all kinds of junk went right through absolutely everything and it was a total catastrophe that happened in a split second with no warning and effectively flushed a heck of a lot of my hard-earned cash down the toilet. The picture here is what came out of the sump... You get the idea...

So I say, think risk, then think that replacing is like insurance, then go and replace the valves. I know it's been debated many times and some keep driving and others don't and you just don't know, but it seems to be a fair bet that it is more age-related rather than mileage-related, especially given my low mileage experience.

Then again, if you are a gambling man, and like to play around with live grenades and that sort of thing, just keep on driving, and wait with excited anticipation for the day when you hear that noise as it all lets go and sounds like a handful of nuts and bolts thrown into a fast-spinning washing machine and watch that magnificent, spectacular, billowing cloud of grey smoke that balloons out the back of the car for a thrilling couple of seconds as all the oil and water merge together in what's left of the combusion chambers. Ah, memories....

Cheers,
Grahame
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wow.. that´s impressive!!!!


You got me scared now..

 

Oh!!! No!!!!
That will make you think twice!!
Next question??
Good source for the valves and $$ expect to pay just for the valves.

 

I bought mine from GT Car Parts

8 exhaust vaves $290
8 intake valve $320

They're somewhat cheaper than the ones from superformance

 

Did you have replace anything else on the top end?

 

I also upgraded to silicone bronze valve guides. That's about $200 from GT car parts.

 

OK, great--something else to worry about!

My 1977 308 GTB (non-cat) has only 28,000 miles, but she is getting on in years.

Is the consensus here to go SS? GT Cars Parts is a good source? Any other vendors/materials options?

Greg

 

I am not sure your car has sodium filled valves.

 

I had one go in my BB512 at 2500 to 3000 rpms in first gear leaving a stop light. 25 grand later, i had all titanium sodium Ferrea valves installed. Do it now before it's too late!

DMAX
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What's the delineation on model year 308/valve type? Are mine already one-piece SS?

Thanks,
Greg

1977 308 GTB USA non-cat