What were the failure rates of the sodium-filled exhaust valves of the 80's?

BLOWN UP SIR !!
I do not use sodium filled valves. I use modern stainless custom made to whatever I need. There are companies that sell replacements, but I had an aftermarket valve fail because it was two piece and snapped the head right off. It was not sodium, just poor quality. No need to use antique tech when it is not seen so originality means nothing.

 

My engine had been rebuilt... Valves were still within spec, so we decided to keep them. New stainless valves are £49 each. What a false economy...

 

Haven’t seen it mentioned in the posts here, and those who have experienced this failure have not specified, but my understanding is that it occurs at a far higher rate on US cars with air injection as part of the emissions system. It was explained to me that cold air from the air injection system blowing on hot sodium filled valves made those particular cars more prone to such a failure. That’s not to say it couldn’t happen to a Euro spec car.

Perhaps rifledriver or someone else could respond to that theory.

It would also be nice to know, at least anecdotally, who here had US vs Euro cars.

At the end of the day, if it makes sense at the time, my valves are getting replaced with modern metal. Although it would be nice to do just for peace of mind, I’m not sure the expense is justified to do it for the sake of doing it, especially of you have a Euro car and the above theory is generally true.