I notice there is a bit of confusion regarding Ferrea valves. They list only 6000 series or Comp Plus for the 4g63. They have the more heavy duty Ferrea super alloy that they only list for the 4B11. I now know you can get these for the 4g63 for those who didn't know.

 

Ferrea Comp plus exhaust valve is made out of super alloy. Here is a break down. i'll take it even futher and break down super tech valves.


This is what I've found. Most say run Supertech due to the inconel exhaust valve which is great against heat. Specifically Supertech uses Inconel Alloy 751. The thing that confuses me as to the reason most say to run inconel and what most don't seem to know is that Ferrea competition exhaust valve is made out of Super Alloy and Inconel is in the Super Alloy family ....but Ferrea Super Alloy is Nimonic 80A based material and is a grade higher than Inconel. Supertech exhaust valve material is rated at 1800*. The Ferrea Super Alloy exhaust valve material is rated at 1850*.