http://store.summitracing.com/partde...art=CCA-503-16
COMP Cams offers a complete line of valve seals, from the stock GM O-rings to the positive-stop TeflonŽ seals. These seals are a must to keep unwanted oil from entering the combustion chamber through the clearance in the valve guides. The O-ring seals use the standard retainer and oil splash shield. The umbrella seals are normally used when a larger-than-stock diameter spring is used.
In the case of a double spring, the positive stop TeflonŽ seals are used. For triple-spring applications, use the smaller-diameter VitonŽ seals.