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I have an early small block 350 that for the life of me I can't get the valve covers to stop leaking. I tried the cork and rubber gaskets and now I'm going to try using a rubber gasket with the steel core. The valve covers themselves are stamped and the heads have studs in them for holding the covers down. I've cleaned the surfaces on the head and valve cover a few different times, tried everything from tightening the nuts down from 45 inlb to 5 lbft. I know the heads aren't bad cuz they weren't leaking before I decided to take the valve covers off the engine a little while ago. Any suggestions on what else I should try? Should I be using a specific pattern for tightening the nuts on the studs?
 

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Try again with the cork gaskets and clean everything with some acetone. Use some Indian Head compound on both the valve cover and the valve cover rail. Don't over-tighten the fasteners just snug them using a 1/4 drive ratchet and socket.
 

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#1 - Make sure the covers are flat around the mounting holes, they distort over time or if overtightened.

#2 - Use spreader bars to distribute the clamping load over more area of the gasket rail. On SBC's I use them with studs and stainless steel lock nuts.

#3 - Use the steel core rubber gaskets.

I had a 350 Chevy and a 318 Dodge both with leaky steel covers, I did the 3 things above in conjunction with each other and no more leaks.
 

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I have an early small block 350 that for the life of me I can't get the valve covers to stop leaking. I tried the cork and rubber gaskets and now I'm going to try using a rubber gasket with the steel core. The valve covers themselves are stamped and the heads have studs in them for holding the covers down. I've cleaned the surfaces on the head and valve cover a few different times, tried everything from tightening the nuts down from 45 inlb to 5 lbft. I know the heads aren't bad cuz they weren't leaking before I decided to take the valve covers off the engine a little while ago. Any suggestions on what else I should try? Should I be using a specific pattern for tightening the nuts on the studs?
Some of these old heads with the as cast gasket rail just can't be stopped because the mating surface is too uneven, rough, sometimes narrows.

The other problem is that with use and age the cover forms dimples around the hold down holes and the cover overall develops twists along the gasket rail that prevent it from evenly loading the gasket. The dimples can be worked out with a small ball peen hammer over a socket or small diameter pipe such that you can flatten them if not pooch the materail up around the hole, just a little bit. The other big thing that will help at this point are hold down tabs that spread the load over more area, <<< 1955-1961, 1968-1981 Chevrolet Corvette Valve Cover Hold Down Tab Set - Engine Mechanical - Edelbrock 55-61, 68-81 Corvette Valve Cover Hold Down Tab Set - 14067-03133273 - PartsGeek >>> You'll need two sets.

These things have a groove and ridge near the outboard side, for the first time I use them I'd put them on groove down to the cover and ridge up to see if they work without maring the gasket rail. If not turn them over.

Bogie
 

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covers leaking?

i always put weather strip adhesive on cover then use thread through holes to hold the cork gasket in place,turn them upside down with a heavy book on them till morning, then smear a slight film of silicone on the head side and install useing spreader bars,next time you take them off rub the thin film off with your finger and reapply film and good to go again,you can do this 3-4 times before replacing gasket!!!i do this all the time to adjust solid lifters ... i hate leaks!!!!!!!
 

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personally i would get rid of the cheap stamped valve covers and get a good pair of valve covers made from a thicker material. and use the rubber gasket gasket with a steele core . also permatex right stuff is a good gasket maker
 

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Valve cover leaks

I have the same problem with a set of finned (Cast) Valve covers, no matter which gasket I use or what sealer I put on. The Covers are flat and clean, the heads are too. 50 years working on cars and I never had a problem like this!
It's only on the left side, I can feel the film at the bottom of the valve cover (Over the header) where it bolts to the head... After it's been run 15 minutes or more.
 

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I have never had SB Chevrolet 327 style valve covers or Corvette finned cast aluminum valve covers leak. I put breathers in the sides of the SB Corvette aluminum valve covers but never noticed any difference.

I seal and stick the cork gaskets to the 327 style stamped valve covers with black gasket adhesive, align the holes in the valve covers with the holes in the gaskets while the sealer is still tacky, then let the covers sit for 30 minutes before installing them. I use the steel spreader tabs under the heads of the valve cover screws just like the factory did. I used that procedure with solid lifters on a 30-30 cam that required valve lash adjustment occasionally. The 327 style stamped steel valve covers do not have breathers and the 327 engines I had and have now only had a road draft tube and did not have a PCV. The only breather on the engine is the push on breather on front oil fill tube. However, I never did any and don't do any long sustained high speed driving on the highways. Never had any leaks...just lucky I guess
 

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Valve cover leaks, continued...

I tried all that is mentioned here... Nope "Didn't work!"
The only other thing I can think of is that the Valve covers are porous and the oil is seeping through!
 

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I don't understand this problem. Valve cover leaking is a oil leak I have never had with a SB Chevrolet engine. I have never had a Chevrolet engine with center bolt valve covers, except on my 1991 S10 Blazer 4.3L engine. No leaks with that one either. I don't use any more sealer than is necessary to stick the cork gaskets to the valve covers. The cork gaskets conform to the irregular gasket rails on the cast iron heads. Let the gasket do the sealing. Don't put any sealer on the engine or on the heads.
 

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I clean the seal surfaces completely... lay valve covers edges on a straight hunk of metal and tap them flat... use RTV/DAP blacksilicone rubber sealant to put them on... don't really tighten the bolts, just snug them enough to keep the valve covers from falling off... let the RTV do the sealing job... give the RTV a couple hours or more to cure before running engine... If doing a race engine and need to run it quickly, will need a different technique...
 

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RTV will leak on valve cover cork gaskets. Better to run them dry than with rtv. Rubber gaskets should also seal dry with flat covers.
Seal the gaskets completely inside the RTV or Silicone Rubber...

Rubber gaskets won't necessarily seal to rough, as cast head surfaces... but sealant will get down in there and fill the pores...

I usually use black DAP silicone rubber on everything older because it cures fast and I keep a lot of it around for use on older black Mercruiser engines... but prolly isn't EFI sensor safe for newer engines...
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I have the same problem with a set of finned (Cast) Valve covers, no matter which gasket I use or what sealer I put on. The Covers are flat and clean, the heads are too. 50 years working on cars and I never had a problem like this!
It's only on the left side, I can feel the film at the bottom of the valve cover (Over the header) where it bolts to the head... After it's been run 15 minutes or more.
We have a set of Holley cast aluminum valve covers on a set of Profiler heads that the lip on the outside gasket surface edge interferes with the heads. Not by much, but enought to NEVER seal. The solution was a thicker valve cover gasket - a PRC 1/2" gasket. You ought to make sure that your cover sits on the head flush without a gasket.
 
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