Sodium Valves? Options

[stugray]

I was once told by one of the resident "experts" on this forum (who has not been around lately) that I should replace my sodium filled valves with stainless. However after visiting the local RSR racing mechaninc (who is machining my case and inspecting my heads), HE said that he goes out of his way to FIND sodium filled valves for race engines. He said that on Air-cooled engines, the sodium helps pull the heat from the heads.

Any comments or suggestions regarding sodium vs. stainless?

I also heard that a simple change from two-angle to three-angle valve seats can increase flow by more than 20% with no other changes to the heads.

Good news is that I should be re-assembling the engine without the deck height problems over thanksgiving weekend. Hope to have it running by Xmas. (IMG:style_emoticons/default/piratenanner.gif)

Stu

[bulitt]

Sodium valves transfer heat to the valve guides. They are hollow and filled with sodium. Sodium of course is corrosive to metal and as mentioned sodium valves probably have a limited life (20 yrs?). Many Ferrari's came with sodium valves.

As far as 3 angle valve guides. The three angles are fairly normal in production cars now. Valve guide machines cut the three angles with a single pass using multiple angled blades. A 20% increase in flow is probably a far stretch. Many racers now go for a 5 angle cut or an infinite flow cut (think 1/2 of a bell curve).
The multi angle cuts allow air to flow around the seat/valve with less turbulence resulting in higher flow at lower valve lift.

In addition to having a multiple angle valve seat you can also have the valve seat face back cut. Looking at a valve you have the normal 45 degree cut on the valve face which seals on the valve seat. A back cut is added to the top of the face so air flowing out of the intake port flows easier over the valve.

It is widely accepted that valve seat cuts should not exceed 15 degrees between cuts. When atomized fuel tries to go around an angle greater, the fuel tends to drop out of suspension. Most three angle jobs coming out of the port are 60/45/30.