QUOTE(Valy @ Nov 21 2011, 08:19 PM)

The sodium filled are still available and not so expensive/
They are after one fails and takes out the entire engine. Been there, done that and added the ten thousand dollars worth of broken parts to my trophy shelf. When a sodium filled valve fails, it doesn't break.. It explodes.
Heads look great to be nearly 4 decades old.. Len does awesome work.
Hell, they look a lot better than the heads that I normally see pics posted of here that have visible cracks in the combustion chambers as their owners brag about the work that was done...
Want perfection? Start with a brand new casting, otherwise you are always going to have some compromise. Len made these look great and the right spark plug hole has been modified for a CHT sensor as Mark stated.. Without that, life is hell.