Bavarian Solutions  [ Cylinder Head Services - Valve Jobs ] The valve job plays a significant role in your cylinder head's performance. The quality and precision of the valve seat geometry will determine how well the valve seals against gas pressure, how fast the heat transfers away from the valve head, and the rate at which the mating surface will wear during operation. Aside from the thermomechanical factors, the valve seat geometry significantly influences the gas flow behavior in a critical area for the gas exchange process. Continuous development using air flow rugs and engine dynamometers has shown that real gains can be achieved by paying careful attention to this area. The venturi area is responsible for approximately 35% to 40% of the port flow.