Need advice on valve cover replacement

This is sort of a followup to a previous post, but I'm going to attempt a valve cover replacement on a GMC 2.8L V6 engine (1985) and need some technical advice. The reason for this replacement is due to a very
persistent oil leak that is thought to be due to warped OE valve covers. The question I have is about the actual gasket material and the best way to insure sealing of the leak.
First off, do I need an actual rubber-type gasket for this or just the RTV sealant? The Haynes manual mentions applying a layer of RTV sealant to the cover and then bolting it on, saying nothing about a rubber or cork gasket. However I know the pre-formed rubber type are sold at auto parts places and such. Do I need to use one or the other, or can I use both to insure a good fit? Since I'm trying to seal of a persistent leak I tend to want to apply as much gasket material as possible but I don't want to go overboard and do something stupid.
Also, I remember hearing a suggestion a while back that you could double up and use two cork-type gaskets instead of the usual one to form a better fit and stop leaks. This seems like a strange thing to do and I was wondering if anyone had any thoughts on that.
If I can use RTV and rubber together, do I apply RTV to the cover and the engine or just the cover side?
Sorry for these ignorant questions but I've never done this before. I am also posting this question to www.s10blazers.com. Thanks,
Casey
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For what it is worth, I had one of the GM Fiero's, 1984 model, which had all sorts of teething problems, including oil leaks.
GM pulled it in for numerous recalls. One of them including resealing the engine, and they did it with RTV blue silicone instead of gaskets. It worked, but I always thought it was a pretty aesthetically unsatisfying solution.
When the block finally cracked, as most of them did, I rebuilt it on a solid block found in a junkyard.
I machined the head sealing surface to make it smooth and replaced the stamped sheet metal valve cover with a cast aluminum one . I also cleaned up the head and opened up the oil drain back holes so that oil didn't puddle up. Then, an ordinary gasket controlled the leaks. All that may not have been necessary, but after all, this was a project, not a repair.
I found that some areas ( like the water outlet from the block) leaked when I tried to use commercial gaskets, no matter how straight and smooth they were. I used the blue goo there, applying a coat, allowing it to partially set and then torqueing down. I had problems with this, as I tried to fill with water after the normal set time. Then I re-did the work, allowing the RTV to set roughly overnight. Never another problem.
If you are going to use RTV, make sure the surfaces are clean and degreased. Don't gob it on...use enough to do the job but not so much it squeezes out internally and gets out of control. You dont want blobs of this stuff to get inside your engine.
Let it cure thoroughly regardless of what it may say on the tube. Err on the side of caution.
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Thanks for the advice. It sounds like the blue RTV will seal as long as its put on properly.

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CNB wrote:

mix RTV with a cork or rubber gasket because the gasket will squeeze out. A cork gasket is fine if you follow directions to attach it to the cover with proper cement. That gasket cement is really contact cement. Perhaps most important is to use spreaders under the bolts to spread the tension on those cheap stamped covers. A tiny leak on the low side of the cover can dump a ton of oil all over as you already know.

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Thanks Al,
Another poster on my earlier post mentioned the spreaders. I haven't looked into that avenue yet but it sounds worth looking into. You say they go under the bolts, I can't picture it. Do you mean under the head of the bolt but on top of the cover itself? BTW, I'm planning on trashing the OE covers and have purchased new Edelbrock #4488 covers to replace them with. With the new covers do you think the spreaders would still be necessary?
Casey

out. A cork gasket is fine if you follow directions to attach it to the cover with proper cement. That gasket cement is really contact cement. Perhaps most important is to use spreaders under the bolts to spread the tension on those cheap stamped covers. A tiny leak on the low side of the cover can dump a ton of oil all over as you already know.

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if you get aluminum covers, you wont need spreaders because they wont flex. aftermarket steel covers that have spreaders welded on obviously wont need them either. one thing - i would recommend using permatex ultra copper silicone over the blue stuff, for several reasons but not limited to, ultra copper is highest heat resistance AND oil/fuel resistance. since i've quit using valve cover gaskets (and on like small block chevys, throwing away the rubber front & rear rubbers that come with intake manifold gaskets) and just went with silicone, the engines i've worked on are so dry it's scary. even on an 89 ford probe that has a big o-ring type valve cover gasket that just would NOT stop seeping, yanking that o-ring & using about a 1/16th inch bead of silicone all the way around works perfectly. put the silicone on clean surfaces, put all bolts in until they just bottom on the valve cover, then give the valve cover a slight wiggle as you press it down just until you see the silicone has made contact all the way around then STOP -- let it sit at least 30 minutes (the warmer the better - it'll dry faster) -- once the silicone has cured up (or at least hardened up enough that it's not all going to squish out), then you can snug up the bolts to desired tightness. no more leaks - just that simple
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Interstingly, this is the exact opposite of what I was told recently. A mechanic I talked to said to stay away from RTV sealant, as it will always leak, but instead go with a rubber gasket and use gasket sealer to mate it to the cover. So now I have the rubber gasket, and installation is slated to begin Friday morning in my backyard. I will keep you informed of the result.
Casey

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If he told you that, he clearly doesnt know how to use it.
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