The Stovebolt Site Forums The Shop Area Engine Shop Correct way to install Valve Stem Seals

1958 Chevrolet 235

I am changing the valve stem seals on my inline six and want to know the correct way to install them. I last had the head rebuilt a while ago and I can see the seals on the valve stem well underneath the spring cups/caps. I see in my shop manual that the seals should be in the bottom of the cups/caps and then the lock is right on top. So do you put the seal on first and then put the spring back on, or do you put the spring with cap on, then the seal, and then the stem locks? I appreciate all the help!

If you're using the original O ring seals, there's a second groove on the valve stem just below the split keeper groove. Install the valve into the guide, put the spring and retainer over the stem, compress the spring, and then install the seal on the lower groove. Put the split locks into place, and GENTLY release the spring pressure so as not to dislodge the O ring as the retainer captures the split locks. When the seal is installed properly, the O ring should not be visible at all. Umbrella-type seals are not original equipment. They slip onto the valve stem and deflect oil away from the top of the valve guides. If you choose to use them, DO NOT install the O rings. It's possible to seal the guides too well, and they wear out from lack of lubrication.
Jerry

Understood. Problem I am now having is that I am doing this with the head installed and the engine in the truck. Keeping the valve in place has been difficult. I have tried using air and have moved on to the rope method. I have had more success with the rope, but the exhaust valves have been the most difficult because it is hard to keep them from moving 1/2" of so. I guess the combustion chamber shape doesn't lend well to stuffing rope into the chamber. Secondly the spring compressor only compresses part of the spring due to the design. It's harder to reach the second groove when the compressor doesn't want to give you full compression.

What is the reason for changing the seals? Have you checked the valve guides for excessive wear, assuming you're dealing with abnormal oil consumption? It might be necessary to go to an umbrella seal, and forget about trying to use the original equipment type. The umbrella seal is much easier to install, since it can be slid down over the valve stem prior to installing the spring. Umbrella seals for exhaust valves are usually shaped differently than those for intakes. They are much shorter, sort of a disc without much of a lip that overlaps the guide. Since there is no vacuum in the exhaust port, it's a lot less likely to get much oil loss down an exhaust guide, at least until it gets extremely worn.
Jerry

Reason: Fresh rebuild with excessive oil consumption. Small to large puffs of blue smoke when starting from a stop. Worse when starting on an incline. Oil can be seen where it was running down from the exhaust ports.

Head was rebuilt by a machine shop several years ago before this rebuild. It all looked fine and wasn't on the old build long before I had to tear it all apart.

I have finished changing all of the seals and it appears that the machine shop assembled the valve and seals wrong, or as it sat on my garage floor the seals shrank enough to slide below where they were supposed to be when I started up the engine. I'm leaning towards the former. I found the seals in the middle of the stem, below the second groove. I'm gonna run it for a few tanks and see if this corrected the issue. Thank you Jerry for informing me of the correct way for the seals to be installed.

I figured why using the compressor and the valves moving was my problem. I didn't cram enough rope into the spark plug hole! I finally was getting the system down by the middle of Cylinder #3. What a pain!

That exhaust valve being recessed up into that oddball-shaped combustion chamber makes it difficult to get enough filler in there, for sure! I'm going to gaze into my crystal ball and make a guess that all your effort won't make a lot of difference, however. The angle of the exhaust valve stem is such that simply putting that little O ring at the top of the valve stem isn't going to make much difference in how much oil finds its way to the top of the exhaust valve guide. I have a sneaky feeling that either the exhaust guide has way too much clearance, or the source of the oil in the combustion chamber and exhaust ports is from somewhere other than the valve guides. I sincerely hope I'm wrong!

Edit:
One quick check for proper clearance would be to grab the tip of the valve stem with the spring removed, and shake it side to side. If there's a noticeable amount of movement at the tip of the valve, the clearance is probably too wide. You should be able to feel a little shake, but if you can see the tip of the stem move, you're going to have a hard time keeping the oil from running down the stem and into the engine.
Jerry