F-body-fan

Hey guys, I am wondering what you normally run for stem seals on your builds?

I built a 350 recently. Fairly mild, with stock ZZ3/corvette fast burn heads, & the LT4 hotcam kit. I ended up using Manley valves, becasue they are a little longer than stock & it gave me a little wiggle room to shim all the springs to the correct installed height. I ditched the metal oil deflector sheilds, they didn't fit the springs in the hotacam kit anyway & I have seen them crack before.
So, I installed the std umbrella style seals on the valve guides. I have done a few engines this way, & never had any issues that I am aware of.

Well, On this engine, I developed an oil leak at the back of the intake manifold. The car was just completed & not even on the road yet. No miles on it. Just an hour or two of tunning time in the shop & that's about it. I pulled the intake to reseal it with a better sealer to end the oil leak. While I was cleaning the port surfaces, I happened to peak down into the ports, & was shocked to see standing oil on each valve that was closed! Not just a little. enough to make a puddle! Now I am second guessing my decision on the umbrellas. I usually use them because I would rather have oil on the guide, rather than it get dry & burn. But I didn't think they let that much oil go by.

What do you normally run for seals? I am considering pulling the springs & putting positive seals on just the intake valves. If I would not have pulled the intake, I would never even have considered or know about this. Maybe this is normal on a fresh engine? I really can't say. Maybe there is a break in period on those seals, But I never thought there was. I am a little worried, & the engine has been apart for a few days.

I can't decide what to do, if anything at all.

Thanks for your input!

91chevywt

I've used positive seals for both valves on mine. Umbrellas are ok, haven't really heard of many problems, but cant say that i've used them. O-rings are junk dont even use them throw them in the tool box they might come in handy some day. In my opinion, use positive seals you shouldn't have any problems, I've had many people tell me to do it that way. If anybody has cooked a valve because they used a positive seal, I'd like to know. Make sure you use lots of oil, and there should be a piece of plastic that comes with them so your seal doesnt get caught on the keeper/o ring grooves. If you dont get the plastic with yours, you could probably use tape or get creative with something

Supervisor42

You find a use for them, let me know. I've got a few hundred.
OHpinion time:
I use umbrellas to give the valve stem at least some oil especially with a high lift cam. You can also get away with more lift without cutting the guides down using umbrellas. High lift cams will put side loads on the stem and wear the guides really fast if they don't have enough oil.
The problem is, the positive seals are just too damn good.
Bear in mind:
I also think that positive seals are the best choice for for a stock engine where oil consumption over 150,000 miles is more important.
Now, anybody got a use for those o'rings?

91chevywt

I think if you know anybody who has braces, and they run out of those rubber bands, they might work for that...

UNCLE TOM

iTrader: (1)

on a daily driver , as my car is , i would use both umbrella and stem seals . some people might not agree , but they are cheap , what can they hurt ? i replaced mine several years ago . i did intake and exhaust the same way . worked great for me . good luck .

Supervisor42

Well, as little as the orings stretch, they wouldn't have much to say

You must be a "belt & suspenders" kinda guy.
You used the umbrellas and the orings, or umbrellas and positive seals?
That may be just the "ticket" for worn valve guides...

91chevywt

Well the o-rings wouldn't hurt anything, but they probably wouldn't do anything after a while so I dont bother. When I pull them out they're little crispy things...they come off the stem in like a million pieces. Does anybody actually use a positive and umbrella at the same time? If I pulled heads apart and saw that I would have to laugh lol...until i realized there was .010" in between the valve and the guide

F-body-fan

I was thinking umbrellas on exhaust & positives on the intake, but I might have taken that post wrong.

So let me toss this question out there.

If you had to guess how much much oil would pass through the guide with fresh ubrellas & no oem metal oil deftectors, what would you expect to find?

I think the problem for me is, I have never pulled apart a fresh rebuilt engine. Fortunatly, I never had a good reason to. With this small oil seep bugging me, I pulled the intake to correct it. If I would have saw just a little oil around the seat, I would think that would be normal. But I have so much oil sitting in there, its literally a puddle. At first I thought I had a bad umbrella, but 5 of the valves look that way & the others are open enough for the oil to pass into the chamber. So either the umbrella do less than I thought, or they actually need to break in & fit the the stem better.

The kicker is, I have not noticed any smoke on start up, so maybe that's more normal than I would think?

I am considering pulling this engine down further to put positive seals on the intakes. Just not sure what to do this time.

Supervisor42

Don't forget stem-to-guide clearance figures into the equasion also (people rarely actually measure it).
Are you sure that this oil puddle didn't get on top of the valves when you pulled the intake? It's easy to do.
I would think that if you had a "puddle" of oil on the valves, you wouldn't be able to see your neighbor's house at startup...
I don't know what the "oil deflectors" do. It can't be much since the engines I've built (and lots of others) don't have them and work just fine.
Maybe the original oring seals only stop oil from the retainer from running down the valve stem and the original uncovered valve guides need to be shielded from splash.
In my book, the oil deflectors belong with those stupid orings... in the trash.
I think some oil got on top of the valves when you pulled the intake and positive seals don't belong on an engine with a performance cam.
But that's just my OHpinion.

Sonix

iTrader: (1)

Ok, now i'm confused, I thought umbrellas were one and the same with those metal "umbrella's" that go right below the retainer.

Anyone got a picture of an umbrella seal, so I know what I just reinstalled on my heads? I have those *tight* positive seals on the intake, and a more loose on sitting on the exhaust (umbrellas?). The exhaust ones just ride on the valve eh? I threw the o-rings on the exhaust, since I pulled o-rings off it, figured I may as well put them on it again now...

Supervisor42

Sure thing. The umbrella seals are all "neoprene". They do not drive down on the guide. The attached picture shows the SBF seals. I use the ones for some cadillac motor (I can't remember exactly which one). They are a little smaller than the SBF ones. They sort of float up and down on the valve stem. This allows oil vapor to lube the guide but not liquid.
Hence the term "umbrella".

Sonix

iTrader: (1)

Oh ok, that makes sense. As I was rotating the engine over to replace the springs here on my engine (shim them up) I noticed that seal was riding the valve and I started to curse. As long as I know it should, that's great.
But why use a ford/cadillac one, something wrong with using the chevy ones? They are designed to fit the SBC setup and ride the guide, so why use the fords?

Thanks, that pic is basically how I set mine up, positives on the intake just like that.

Supervisor42

No no! The positive seals are supposed to be a press fit on the guides and stay there.
The "all rubber" umbrellas float.
Why use ford & cadillac umbrellas?
SBC's never used umbrellas so you have to ask for "ford" or "caddy" to get the umbrellas.
Why use umbrellas when the newer positive seals are so much better?
Newer seals work too good. Not enough oil to keep the iron guides from wearing fast with a high lift cam.

Pat Hall

iTrader: (31)

Another option you could consider is the viton rubber, positive type seals. They're nice because they're a positive seal design, but they're not as stiff as the teflon ones. Edelbrock has ones that fit the stock guide boss without any machining. If you have the guides machined for positive type seals, they also sell that style, and Manley sells really high quality, positive type, viton ones if your budget allows. I bought a set of used AFR's from a guy who had teflon seals on them, and you can actually see scuff marks on the valve stems, and one of the seals was broken off at the top where the little spring is. I'm going to give the viton ones a shot on my heads. I figure with them being more pliable, they shouldn't scuff the valve stems, and hopefully allow a little more oil in the guides. In fact, I went to AFR's website, and they said not to use teflon seals on their heads.

F-body-fan

I am starting to think that more oil passes through the guide than I originally thought, & it must be a somewhat normal amount. I decided to put the engine back together & wait until I have a few hundred miles on it to do anything further with the seals. To my surprise, There was no smoke on start up after getting the intake reinstalled. I guess it takes a bit more oil to be a problem, at least more than I used to think, that's for sure.