Valve cover leak has defeated me for 10 years, need help!

[Kern Dog]

I have the cast aluminum Mopar Performance valve covers and Edelbrock heads.  I have had this setup since 2004.
Gravity being what it is, I never saw any leaks near the top of the VCs. The leaks I'd see were always along the bottom and rear edges. The Edelbrock heads have a machined gasket rail. I don't know if that helps or hinders a good seal.
Aside from the "Right Stuff", I stumbled upon something else that helped.....
The mounting holes in the valve covers are loose enough that the VCs can actually slide around a bit before the bolts are tight. In my case, just resting the VC on the head THEN tightening the bolts often resulted in an offset of the gasket and head. Tightening the bolts sometimes deformed the gasket and induced a leak.
I found that this worked: I put a thin layer of The Right Stuff on the valve cover, then lay down any one of the black fiber gaskets. Let it sit about 1/2 hour. This stuff sets up quick.  Rest the VC on the head, then push the VC up toward the carburetor and tighten the bolts. This made the bottom rail line up with the valve cover and gasket.

[b5blue]

With my milled edge Sidewinders and Cal Custom VC's it took awhile to figure out the holes are a bit shorter for compression of the gasket. I'm using the rubber gaskets with steel reinforced centers as they hold their shape and are a bit thicker. 

[AKcharger]

- Nacho - I am completely out of answers on this. I NEVER had an issue on any cast Iron heads, only this engine and the aluminum heads is the only discriminator
- Kerndog - I'm going to follow your lead with the sealant. if I do gasket to cover and Gasket to head it SHOULD work..we'll see
- B5 blue - the M/T's are the last gasp, if they don't work I don't know what to do. If next try doesn't work I'm trying you "seal cover/grease head" method

I've been cleaning all the oil out of the head, I think that MIGHT help. figure perhaps the rail is a little oily and sealant isn't "grabbing"

[b5blue]

   If ya try my way clean all that silicone off of everything and I use the same stuff as corney used but in a toothpaste type tube. Seal the rubber gasket to the VC and lay it on a flat surface till dry. A very light film of grease on the gasket allows it to seat under compression. (The grease is not sealing, it allows slight shifting.)

[AKcharger]

OK, gasket is sealed to Valve cover. I did note the hard gasket was mis-align with the cover unless it was forcibly positioned, so this would account for the massive leak. I have it curing up tonight and will try B5's grease method tomorrow

[AKcharger]

OK, update!
B5's sealant on top and grease on bottom seems to be working. I did the pax side and ran it for about 15 min. There was an ever so slight bit of smoke but I think that's the oil from previous leak burning off. Now doing Drivers side cover...I'm hopeful!

[AKcharger]

Final update - still leaks 
Good news its not as bad, but still there on pax side. I cleaned it let it run/burn off and if I drive at higher RPMS I can open the hood and see a few drops smoking on the manifold, but not the cloud it used to be so I'll call it good and accept defeat
Drivers is holding well.
Thanks for the tips!

[b5blue]

Did you check the gasket to head shape? (Lay the gasket on the head and align screw holes.) 

[AKcharger]

Did you check the gasket to head shape? (Lay the gasket on the head and align screw holes.) 

Well if mean lay gasket on head and does it look right...yes

I can't figure it out...and I'm super smart! I've never ran into this problem on any other vehicle in my life.
- 3 sets of valve covers
- 8 sets of gaskets from cork to composite
- valve cover bolts
- valve cover studs
- 4 diffrent types of sealant
- no sealant


I can only assume it's the head casting by 440 source, only variable left but im not pulling them off for a leak

[b5blue]

Look under the intake. You can have oil work it's way up and on to the pan. In the rear it can just make it out next to the valve cover. 

[Mike1268]

I use cork and "Permatex Aviation Gasket Sealer" on both sides of the gasket.  Never had a problem.

[AKcharger]

Well, it's still leakin, I'll try anything, thanks!

[b5blue]

I noticed using Mopar brand valve cover (black) bolts on Sidewinder heads and Cal Custom (vintage) covers with the black rubber steel reinforced gaskets were just a bit long. It stopped proper tightening just a bit. (Really pissed me off but don't know who to blame.  ) 

[AKcharger]

Still leaking BTW, 12 years now, even had a shop try 2 times, they had no better luck

[LaOtto70Charger]

That sounds like my transmission leak I have been missing with for 20 years

[Dino]

The edges on the heads are narrow and rough. It makes it almost impossible to get a proper seal. I thought about cutting a groove into the seals so they would slip over the edge a bit.

[AKcharger]

Thanks Dino, I'm gonna give it one more try and say "F it" and swap out the heads...its the only variable there is. As soon as I'm done battling my EFI demons I saw a trick about pumping air in the block to fi d the exact location of the leak.

[4cruzin]

Some good ideas here . . fighting this same problem now.   

[will]

I would put rtv all the way around the bolt holes. Otherwise BTDT.

[AKcharger]

Ok EFI battle won, now to tackle this. Suggested method is use weather strip to seal gasket to cover, cure 24 hours then use black gasket maker and seal to head tighten a bit...24 hours then tighten fully
 

[b5blue]

Check bolt length carefully. 

[AKcharger]

OK lets see how this goes...gasket sealed to cover with weather strip sealer, head is SPOTLESS and black gasket maker applied. I'll let it sit 36 hours to cure. Finger crossed

[b5blue]

I used black rubber gaskets with steel cores. 

[Kern Dog]

The black fibrous gaskets don't deform like the softer designs. I used to use cork and seemed to have good luck with them but only if they were coated with RTV and let to set up before installing.
Sorry if I have already mentioned this here but the one thing that made all the difference for me was not just the gaskets themselves but the positioning of the valve cover.
The mounting holes allow a degree of movement that can result in a misalignment from the valve cover to the head. If the covers are allowed to slip down away from the intake and toward the exhaust, the bottom flanges of both the head and VC are offset, Gravity being what it is, this increases the chance of a leak. I've found that I need to pull the VC up toward the intake before tightening down the bolts. Maybe my mounting holes are off center slightly but this reduced my leaks by a huge margin. I've done this on other engines and it seems to have helped there too.

[John_Kunkel]

For several decades, the factory has used no gaskets on some installations with stamped metal covers. On problem leaks, instead of a gasket, one might try a really thick bead of RTV allowed to skin over before installation and only tightening the bolts enough to compress the bead. Allow to sit overnight before running.