The Stovebolt Site Forums The Shop Area Engine Shop Valve Seals

I want to replace the valve seals. I have both the umbrella and O ring type of seals. Am I correct in my thinking that you use either one or the other, but not both at the same time?

Correct.

Jim,

It's not unheard of to use both together..makes little difference, they won't interfere with each other.

Stuart

Use one or the other, NOT both together. It's possible to starve a valve guide for lubrication by too much sealing, resulting in wear, galling, or actually sticking of the valves. The original method was a sheet metal shroud around the top of the valve spring, and a rubber O ring around the stem to prevent oil from leaking down the valve stem. An alternative method was to remove the metal shroud, and add an "umbrella" seal that fits tightly around the valve stem, and rides up and down with the valve. This seal sheds oil off the top surface, preventing oil from puddling on top of the valve guide. The third method is the "positive" seal, which clamps to a machined shoulder on the valve guide, and wipes oil off the valve stem as it passes through a spring-loaded lip on the seal. Use only one of these types of seal, don't double up on them.

With good, tight valve guide clearances, all that's needed is the original O ring system. Somewhat worn guides can benefit from the umbrella or positive seal systems.
Jerry

When using the umbrella seals do they get pushed all the way down the valve stem, or do they seat in the groove where the O-rings were?

Push the umbrella seals all the way down against the valve guide. As soon as the valve opens the first time, the seal gets pushed up to the correct running position.
Jerry

Jim,

The stem seals I have used slipped all the way down the valve stem, clear to the top of the valve guide. When the engine is started, the travel of the valve will set the final location of the seal.

We called these "Ford" type seals. They wear a relatively soft plastic umbrella style that merely pushed over the valve stem before installing spring, retainer and keepers. They travel up and down with the movement of the valve.

I don't remember ever seeing a stamped steel shroud around the valve spring on a Chevrolet six. I have seen them on the V-8's though.

Stuart

OK, thanks everyone. I did it right. I used only the umbrella seals pushed all the way down. I used these seals because the valve guides are worn. I'm almost done, three valves to go.