I've heard of Ford HD 292 engines having exhaust valve stems that were sodium filled.  Cliff reported in another thread that the stems were ~7/16 in diameter, but I haven't seen any prior to this.  WoW!   

Click the link below to see pictures of the engine for sale on eBay with a cylinder head picture that shows the size of the exhaust valve stems adjacent to the intake valve stems.

http://www.ebay.com/itm/Used-Ford-292-V8-Engine-/112160346844?hash=item1a1d4712dc:g:5OsAAOSwOyJX9~cv


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Ted redid a set of 471 heads for me putting thicker valve guides in to take the normal valves. Seems a lot of the decent low compression (supercharger) heads ended up on trucks with the sodium valves. Trucks are much more labor oriented and lower speeds. Although I don't really know why they did them.

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire