Valve Stem Seals

[corsair231]

Guys, I did the valve stem seals on my Sy and all was good as far as the start up smoke show. I do have an issue with a low speed miss that I am still chasing that I found last month when I drove it to Richard Clarks place for the Buick meet but that hasn't been bad enough to keep me from putting around here and there though. So now after about 400 miles total the truck has started to smoke again when cranked. I though that maybe I didn't get one of the seals on good enough and it pushed off the seat. Anyway, started pulling it apart and when I pulled the springs on number one I found that on both the intake and exhaust valve, the o-ring seal had come out of the groove and was pushed to the bottom of the stem. What could have caused this? The keeper moves with the end of the stem and it should stay in relatively the same orientation so it couldn't push the seal down and the keeper should keep the spring from contacting the seal. If there was too much valve lift then it would seem that the seal would have been pushed to the top of the stem above the groove. There is no noticeable wear or stem movement in the guides and the valves rotate easily through the range of motion so nothing is bent. I know they were in the groove when I put them on and the snap on seal was still in place. Could the O-rings be the wrong size? I used Fel-pro seals, which are usually pretty spot on. Anyone else had any problem with them? Anyway, I ordered a different brand which will be in next week and I'm going to give them a try. On the plus side of this, I have gotten pretty good at pulling the valve covers off and thank goodness I changed the hard i/c pipes out for heater hose.

 

[No disintegrations]

I thought that vintage of 4.3 used the umbrella style seals which ride up and down with the retainer. Got any pics of it apart?

 

[corsair231]

No photos but they do use umbrella seals on the intake valve only. They snap in place on the shoulder of the rocker pedestal. It remains stationary and it was still in place. Both intake and exhaust have a groove just under the retainer for an o-ring style seal that does ride up and down with the valve. It's job is to be a damn to keep oil from the top of the valve stem from running down the stem and pooling on the top of the guide. The exhaust valve doesn't see vacuum like the intake does so most cars only have that type seal, if any at all, on the exhaust. The intake, since it is under vacuum, tries to suck oil in so it usually has one of those positive lock umbrella seals that wipe the stem as it travels up and down and these have an o-ring on the intake stem as well. Since the O-rings travel up and down with the valves something either had to push it or pull it out of the groove and to the bottom of the stem. The o-ring size is so much smaller than the inside diameter of the valve springs that outside of coil bind distorting the shape of the spring [making it look like this ) ] when it is compressed, I can't figure out how contact could happen. My truck has the stock cam and rockers so I don't see how there is any way it could get into coil bind. There should not be enough lift to stack the spring solid and make it deform plus that should bend the pushrods if it did and mine are okay. The only other thing I can think of is that the valve action itself may have just shook them out of the groove and to the bottom but honestly, that doesn't seem very likely either, unless the O-rings themselves are wrong and don't fit in the groove tight enough, but still???? I've never had problems out of Fel-pro but I've got a different brand coming to replace these just in case their O-rings are wrong.