Is it true that cossie YB exhaust valves are sodium filled and if so what advantage does this offer?

Whats the difference between standard valve guides and the bronze versions?

 

I've read somewhere that they are sodium filled. Supposed to aid heat dissipation or something.

 

Hi,

Exhaust YB valves are sodium filled to help heat transfert between valve head and stem. Because sodium is a metal, and is liquid state when engine is running.
In same idea, bronze valve guide is better for stem slipping, and is better to transfer heat between stem valve and head case.

Regards.

Claude

 

Early Cosworths had a bronze type alloy for the guides and later ones has cast iron (cheaper and longer lasting). Nover use pure bronze guides as they wear away very rapidly.