The Stovebolt Site Forums The Shop Area Engine Shop Valve stem seals

I've been reading different posts about which type of seal is better, umbrella or o ring. Can someone explain how each one works? Does the umbrella just got over the valve guide or in the groove where the o ring would go? If I use the o ring type does the retainer slide up and down over the o ring? The ones in the head gasket set are bigger than valve stem is that normal? I haven't dug this deep in an engine before. Thanks for reading.

The O ring seals fit into the second groove on the valve stem, the one below the split lock groove. It's supposed to prevent oil from running down the valve stem and puddling on top of the guides. Umbrella seals are supposed to have a tight enough grip on the valve stem to ride up and down with the valve and deflect oil away from the top of the guide like an umbrella protects you from rain. There's a third design called a "positive" seal that clamps down on the top of a machined valve guide and keeps a firm grip on the valve stem as it slides through the seal. Umbrella seals for intake valves usually have a deeper cup shape than the ones for exhausts, but both should be a snug fit on the valve stem.

It's possible to seal valve guides too well and starve the valve stem for lubrication. Then the valve stems and guides wear out from running too dry. A properly designed seal allows a tiny bit of oil to run past the seal and keep the guide lubricated. If you use umbrella seals, DO NOT also use O rings, etc.
Jerry