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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
my intake seals don’t seem to want to go over top of valve guides very easy. i’m afraid of breaking them. how far should these be pushed on? heads are factory, never had work dine to them. here is pic of the guide. part number has been triple checked.
If that's a factory style seal then it gets pushed on until the inner part bottoms on the guide. I've always know factory seals to be those cheap umbrella style seals.
thanks. it is same as factory intake. does this just meet the valve guide or go over top of it, which would push it down even further. the factory guides are still intact and they seem to be over the guide. it’s hard to get them off.
thanks. it is same as factory intake. does this just meet the valve guide or go over top of it, which would push it down even further. the factory guides are still intact and they seem to be over the guide. it’s hard to get them off.
Are you saying the valve guide material protrudes past the casting?
Can't say I've ever come across that however, the valve stem seal is sized to fit around the valve stem. The O.D. of a guide insert would be considerably larger than the valve stem itself and would never (or should never) be assembled so as to fit around it.
Should it be pressed down over this protrusion to where the half circle is located? Should if fit over top of that? Should the bottom of the seal meet the red half circle? My factories were stuck on that area, but maybe because they were old? (sorry, this is a vortec head, best photo I could find)
They should be pushed down as far as they can go. When everything is assembled, depending on cam lift, the bottom of the retainer can make contact with the top of the seal. It shouldn't, so at max valve lift, the bottom of the retainer should not make contact with the valve seal.
Then again, if they're not pushed down enough, they may get hit by the bottom of the retainer and it will just hammer them down and possibly cause them damage.
well, that definitely makes sense, but i can’t seem to push down to red circle. are these things designed to rest on top and “float” or are the supposed to be anchored by the friction caused by pushing them down to red circle ?
I used silicone umbrella seals last set I changed on my LB9. Worked great. Enginetech S2806. Never going to disintegrate or wear out. No valve stem movement and the silicone is impervious to everything including heat.
GD
Last edited by GeneralDisorder; Mar 11, 2019 at 11:50 PM.
i think i have been misled. everywhere calls these stock replacement and refers to them as umbrella. jegs, summit, rock auto. even fel pro website. they are 72527 felpro. but when i just went to felpro forums them have a different story.
Yeah and then Fail-Pro says to use 72526 for the exhaust side - which are umbrella seals......
Both the 72526 and 72527 are plain old rubber seals - prone to deteriorating over time. And the 72527 will wear also as it's a stationary seal with the valve moving through it.
Check out the EngineTech S2806. It's silicone, and has a spring to keep it tightly on the stem. There is no relative movement between stem and seal. And the silicone is impervious to heat and engine fluids.
Thanks for your help guys. After further inspection, it turns out I had them down further than I realized. Regardless, i took a 7/16 long socket over top the seal and gave it a few whacks with rubber mallet to seat it nicely just like the video shows above. These are the proper fitting seals. They are also not rubber, as jegs and summit indicate, they are high grade materials.
One thing I was considering while doing this, (you have a lot of time to think while doing valve seals) is that GM may have designed the exhaust seals as umbrellas to allow for oil to pass thru easier. I know that some engines are designed to burn a small bit of oil as part of its lubrication system. I don't know if GM did this for small block chevy engines, but putting a positive seal on it could hamper this process. Do I know this? NO, I don't know this. Just considering it, that's all.
One reason for considering this, is GM used positive seals on intakes in 1990. how do I know? that is what was in there. But guessing umbrellas for the exhaust, because all I can see is the stain of what once was a seal.
Back to the seals!
Last edited by LiquidBlue; Mar 12, 2019 at 04:41 PM.
Exhaust isn't as critical. The intakes have vacuum under the valve as air is being pulled into the cylinder. This can pull oil down the guide. On the exhaust side, there's usually pressure from the exhaust gases so the only oil that should get down the guide is residual oil after the engine has been shut off. A basic umbrella seal on the exhaust valves is more than enough unless you have some really worn out guides.
I don't burn any significant amount of oil using umbrella seals on both. My LB9 had positive seals originally that were shot so I changed to the silicone umbrella seals and they work excellent for me.
my factory intake lower seals seem to be in very good condition, the upper intake seals were intact, but brittle. The exhaust, lower disintegrated, upper, intact but brittle. wasn't burning oil, just occasional puff on start up.
was thinking another reason factory doesn't use positive seals on exhaust is there would be once they disintegrate, there would be metal floating around on the valve stem.
