390 valve cover leaks

[David Greenburg]

I know valve covers on these engines are touchy, and I don't expect a 56 year old engine to be drip free, but I've had a slowly worsening valve cover leak on the lower rear edge of the driver's side valve cover. I have tried retorquing to spec. without improvement. I am not using any sealant, as I was told a while back that these valve covers should seal without using any sealant, and that doing so  just amounts to a temporary fix.  So I'm wondering if anyone else is managing to get a good deal without using any sealant.  The gaskets on the car are cork and only a couple of years old.

[savemy67]

Hello David,

I have not driven my car far enough to adequately determine if the one year old cork valve cover gaskets (without sealer) on my 429 will hold up long term, but so far, no leaks.  Did you replace the gaskets yourself?  Did you ensure that the valve cover flange and screw holes are in good condition?  What brand of gasket did you use?  Depending on the quality of the replacement gasket, and the amount of miles you have driven, it may be time for new gaskets.

Respectfully submitted,
Christopher Winter

[The Tassie Devil(le)]

From my experience, you will need to replace the gasket as re-torquing the bolts down will only exacerbate the leak, as you have found.

Once gaskets have "set" and become hard, and lost their sealing, tightening will only lead to bending the metal around the fastenings.

When using any gaskets I always use a smear of silastic on both sides of the material to aid in sealing.

Once the cover is on, and the fastenings tightened down, any further tightening must be done before the gasket takes shape.   Usually after the first heating cycle.

With the Tin covers, one must always check for distortion and rectify before reuse.

Bruce.

[Dan LeBlanc]

A good friend of mine has had better luck cutting his own gaskets from a thicker material than the pre-made gaskets. His valve covers do not leak on his 62 after doing this.

[russ austin]

Give Best Gaskets a call. They may have the non cork gaskets.

[Scot Minesinger]

There is an old mechanic's lesson passed down to me on this forum to repair the valve cover, trans pan, oil pan, and etc. if it has been deformed by over-torqueing in the past.  What happens is the metal around bolt hole deforms and contacts the mating metal surface fails to compress the gasket all resulting in leaks.  In general a leaking valve cover or whatever can almost never be repaired by re-torqueing has been my experience.

You want to drive that bell shaped deformity around each hole so it does not protrude down into the gasket side of the metal valve cover.  Turn the metal valve cover over so that you are looking at gasket side, place a piece of wood (pine, not oak) against the part of the pan where the bolt head would normally be (you may have to use a 5/8" or some specific thickness as the wood must contact with this surface flat.  Then place the round part of a ball-peen hammer against the gasket side of the hole on the pan, on the hole so the wood sees the round part of the hammer.  With a nylon (not another metal hammer - very dangerous) hammer smack the other end of the ball peen hammer and you should see the bell shape around the hole go up and protrude just very slightly onto the bolt head side of the pan.  Do this for all the holes.  Then re-install with new gaskets, and you should be good, works every time for me with dry gaskets.

[David Greenburg]

Russ - I've been told cork is preferred for these cars, in part because they are thicker, and there is an issue with the modern gaskets being thinner than the originals.  But I take it you've had a different experience?

Scot- I've always felt like straightening valve covers is kind of hit or miss (literally and figuratively).  This sound like a great approach.

As usual, learning a lot here. I always considered replacing valve cover gaskets based on age, not based on the number of times they've been removed tightened.  Also makes me think my overheating experience on the way to the GN may be contributing to the problem.  I didn't notice this leak until after that.

[The Tassie Devil(le)]

Ah ha.   Overheating will cause more problems than we think.

There is nothing worse than cooked gaskets.

I worked on a '71 Eldo that the owner cooked, and even the wiring loom that runs along the intake manifold was melted together.   The heating was so bad that the valve springs had lost their tension, and could be pressed down with finger pressure.

Bruce.

[Rod Dahlgren #19496]

Valve covers must be flat- especially across the bolt holes. Small amount of hi-tack or trim cement to get the cork gasket to stick to the valve cover--  NONE on the head. Be sure the covers are not cracked near the bolt holes. I have seen this from covers that have been bolted down too tight.
NONE of my cars have leaking covers--  The 429 covers are the most difficult to seal.. Mine don't leak