Supertech Black Nitrided Intake Valve Set of 8Production of Supertech racing valves begins with a one piece forging, where the head of the valve is forged under a slow two step process to keep a good material grain flow. The forging is then CNC machined in several steps to ensure the precision of the final dimensions. We then do another heat treatment for stress relieving followed by a nitride hardening treatment (or coating process depending on the application). Lastly, we do one more grinding,