This thread is mainly about adding umbrella seals to the valve stems. But first, a short story. Bought an O T vehicle running a small block 400. I did notice that it smoked a bit from the p***enger side exhaust. Not just on start up, but constantly. That was ok because it helped bring the purchase price down. Got it home and did a few things to it including a new set of spark plugs. The plugs read great on the driver side but the p***enger side was ugly with number eight cylinder the worse. Ran it for a few weeks and pulled the plugs to see where I was with this thing. Once again, the drivers side plugs were perfect but the number eight plug was totally fouled out. the number six plug was a little better, four better yet and the number two plug was cleaner than the rest. I'm not as bendy as I used to be so my plan was to pull the engine and put it on a stand to work on it. But I thought, just pull the one head and check it out. Well that's not as easy as it used to be. My body has more creaks and groans than a haunted house. Anyhow, I pulled the head. Set it on the bench and there, to my amazement was a round gasket from an oil bottle sitting there, partially plugging the oil return hole at the back of the head. The way I see it, this gasket was causing oil to pool at the rear of the head, causing the oil fouling as it was. Cleaned it all up and hand lapped the valve seats for the hell of it. Purchased new valve stem seals and a set of umbrella seals too. The original stem seals were hardened and needed replacing. The valve stem to guide clearance is real nice. So my question is, Should I use the umbrella seals too. I would think that these seals would cut off lubrication to the guides. Or do they let some oil p*** by. I don't know. What do you all think?
Umbrellas worked for I don’t know how long on Mopars,,,,,,,the Mopars are known for not having a lot of problems with valve guide wear . I’ve always used umbrellas on Chevies also,,,,,never had any problems . Tommy
Correct. The drain back hole in the head was 3/4 of the way covered up with what appears to be the gasket from the cap on a quart of oil. It was about the size of a quarter. The oil fill hole is on this side as well. My concern here is whether or not to use umbrella seals in conjunction with the normal valve stem seals. I fear lack of lubrication to the valve guides if I do. In the past, I've used umbrella type seals on older, tired, half wore out engines just to cut down on oil consumption. Seemed to work for awhile. I think that, for now, I'll put it back together without the umbrellas since the fit between the valve stem and guide is good. Could always install them later.
There are all sorts of valve stem seal available for SBC heads , some seal better than others , some last longer none that I'm aware of cause trouble with guides not getting enough oil !
The seals wipe just enough oil lub on the stems. They don't "cut off lubrication". Don't fear using them.
If it is stockish I have put both on for years without problem. Have to watch which style you put on if there is any lift to the cam. Make sure the diameter isnt to tight to the valve guide OD. Some umbrellas will act like a pump and actually force oil down the guides.
Chevy used umbrella seals on the exhaust valves from the factory in the 80s. Never saw any problems with them. They had Viton type positive seals on the intake valves, also.
A true umbrella seal Is attached to the valve stem and goes up and down with the valve. When the valve is in the closes position or seal up the oil mist gets up around the valve guid for lubrication. When the valve is open,seal down it blocks more oil from being pulled in. I’ve installed thousands with no problems. Also use the small o-ring on top of the valve. A positive seal that sometimes get confused as an umbrella seal is attached to the guide and the stem rides in it. As mentioned enough oil gets p***ed to keep the guide lubricated. Chevy started using them on the late 80s and there didn’t seem to be any problems.
If I remember correctly, I had issues with #8 fouling on a SBC due to that cylinder ****ing transmission fluid up the TH350 vacuum modulator line that was connected to the intake. In my case, I can't honestly remember if it caused it to smoke or if it just made the exhaust smell strange/bad, that could depend on how bad the modulator valve is. It does sound like you've found the cause and I don't know what transmission you are using but this might be something worth checking if your problem isn't solved.
Someday I’ll tell the story of a not so knowledgeable 16 year that was told he needed to change the stem seals on his 307 and why he did what he did, and even when doing it, just didn’t seem right. That same kids dad brought me, er, him home a few Motors Manuals and I , er him did it again.
I had an OT Chevy wagon with a 350 I bought for junk $$. The owner said the engine was bad and fouled the #8 plug. To make a long story short, the car was used on short hops and not at highway speeds. I went one heat range up and ran the hell out of it. It still puffed a little on cold starts, but it ran strong.
From what I know about umbrella seals is they keep the majority of the oil coming off the rocker arms from running down the valve stem. They didn't really seal off the guide, same with the small O-ring seal. They just deflect the oil way from the guide. A true positive seal rides tight on the stem and is pressed on to the guide, but even positive seals let some oil past to keep things lubricated. Theres plenty of oil vapor in the engine to keep the guides work, the umbrella seals won't effect that. And as you found out, no seal will help when the guides are " under water " or in this case, under oil.
When the earth was till cooling we had lots of problems with small block Chevies and Y block Fords getting clogged drain holes. Short trips and infrequent oil changes made sludge in large quan***y to block lots of holes. A large amount of condensation can build up in a hurry if the engine doesn't warm up to operating temperature. Water and oil makes "Jello". "Jello" makes sludge. Sludge plugs things up. It's that simple. Frequent oil changes are required.
If you do away with these go with the umbrella shields https://www.bing.com/images/search?...E689F29&selectedIndex=3&ajaxhist=0&ajaxserp=0
We had talked about the possibility of it ****ing oil through the intake gasket. Thats one of the things that I was going to look for.
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