308 Sodium Intake & Exhaust Valve Issue?

All 308's including the GT4 came with sodium valves,Ferrari stopped using them in the QV onwards though..
Here is a few threads about them..

http://www.ferrarichat.com/forum/threads/would-i-have-sodium-valves.395864/

http://www.ferrarichat.com/forum/threads/what-were-the-failure-rates-of-the-sodium-filled-exhaust-valves-of-the-80s.361645/

http://www.ferrarichat.com/forum/threads/sodium-valves-curious-to-know.188739/

 

Here's what I found in my exhaust. The previous owner had a very expensive engine rebuild.
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I also have a '78. Mine has 50,000 miles. Also a concern of mine. It's just the exhaust valves. Lots of cars used this technology and some still do today.

The issue, as best I can tell, is that the Ferrari ones of the 308 ilk were "inferior". That, I think, combined with improper maintenance (not checking valve clearances as prescribed) and abuse (repeated high RPMs) contribute to abnormal failure rates for 308s. But this is only my observations hanging around here for awhile.

So, it's on my "to do" list. But at the moment I'm still driving my car .

 

Even the Vipers used sodium valves. Common for race car setup to use them. From what I understand they are to be better, and are not crap.... Ferrari would have never put crap in there cars as this was racing technology. I can't recall where I read the Data, but the breakdown occurs from them not getting hot enough in road use like on race day causing them to be not ideal for road use. Feel free to correct me if I'm wrong, or if someone finds the article/data point that shows why they are an issue in road cars.

 

Ferrari may not have intentionally used inferior parts, but - as is often the case when experimenting with cutting-edge race tech - sometimes technologies' shortcomings don't become evident until after years/many miles of wear (F355 valve guides, anyone?). The idea of sodium valves is that the sodium will act to absorb and dissipate some of the exhaust heat from combustion. However, generally , manufacturers today would use larger-diameter valve stems so that they could thicken/reinforce the walls. Ferrari didn't want to do that, so they just hollowed out standard-size valve stems, making them brittle if the valve goes out of adjustment and makes contact with anything. Sodium is explosive, and a broken sodium valve can essentially destroy an engine. True catastrophic failures are rare, but they DO happen and have been documented here by many seasoned techs. It is true that this happens mostly in engines that frequently get pushed to their limits, or where the valve clearances aren't properly adjusted. I've also noticed that a lot of "failures" discussed here occur when a valve is dropped on the floor, struck on a workbench, or otherwise impacted in some way that doesn't mimic normal engine wear. To make a hollow valve, the head had to be welded onto the hollow stem, and in this case two joined parts were weaker than a single stainless part. Some call solid stainless replacement "cheap insurance" against engine failure, although a $8-10k head rebuild is hardly cheap.