I have the late valve. It was so stiff that it could not be moved with the dash lever. I could not see how to take it apart, but a little spritz with WD-40 immediately freed it up and she's worked like a champ for years now, leak free.
For your old style valve, maybe a fix like this:
http://pantera.infopop.cc/eve/...274/m/6391075316/p/1
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