[Vwdiesel] NA exhaust valves for a TD head?

[Tim Hicks]

The non-turbo head is cast in aluminum-alloy. The Turbo has a stronger, sodium-injected alloy. Different materials are also used for the Turbo's valve seats, the pre-chambers and the turbo’s valves made of a special metal called Resistal and the exhaust valves are reinforced by a plasma spray during manufacturing process.
 
Tim