Rubber gasket vs. a cork gasket

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christopher.brandon

christopher.brandon

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Hello all,

I was wondering which gasket for a valve cover is better: rubber or cork? Or is it just more of a preference? Common sense tells me that a rubber gasket would be better, but wanted to get some expertise before I change it out.

I noticed that ther was oil under my car, and that it was dripping down the side of the block. I made my first attempt at ever installing a valve cover gasket. To say the least, I didn't do a very good job, and she is leaking again. I made a rookie error of thinking that tightening the bolts even more would make a better seal. There is that common sense again.:eek:ops: Anyhow, I want to right my wrong and do it again, but I want to make sure I get the best gasket for the job. The original gasket was cork, and rather new, as well as the last one I put in. I suppose that is why I am leaning towards a rubber gasket.

The engine this is for is a 225 slant 6.
 
I HATE cork gaskets.
Clean the cover real good of all oil and junk.
1/8 in bead of red silicone on the cover (And all the way around the bolt holes)
Rubber gasket then another 1/8 bead on the engine side of the gsket and slap er on wet.
When putting the silicone on, smooth it down a little with your finger to spread it a little.
Tighten in a rotating pattern like you would a cyl head just till snug (Not tight) a little at a time until they are all about the same.

If you do it this way, after a day you could take the bolts out and throw em away and it will still not leak. :)
Did it once to prove it to someone. (Drove it 15 miles to his house and back)
 
Cork always ends up absorbing oil and eventually leakin. GHEY.
 
Your type of valve covers will make a difference too. I know the stock covers on my 318 and 340 with the thinner rubber gaskets hit on the intake and will not seal. The thicker cork gaskets bring the valve cover gaskets up high enough so they somewhat seal.
 
i hate the rubber gaskets... never can get them to seal even with silicon on both sides... with the cork i just silicon it to the cover and its reusable a half a dozen times...
 
I always use cork.As 805 said I permatex the gasket to the valve cover and reuse it many times over.Cork will only leak if you over torque your valve cover.If you silicone both sides, have fun getting it apart later.


Jim
 
If find that the cork works better than rubber simply because it doesn't
Squish so easy, rubber seems more suitable for grooved applications
 
Thank you for all of the input!

I do not have a torque wrench, so what is the general "rule of thumb" for proper tightening? I have heard that you want to get it finger tight, then give it a couple more rotations with a socket wrench. Is that about right, or not?
 
christopher.brandon said:
Thank you for all of the input!

I do not have a torque wrench, so what is the general "rule of thumb" for proper tightening? I have heard that you want to get it finger tight, then give it a couple more rotations with a socket wrench. Is that about right, or not?
Click to expand...

finger tight and then take it snug...
 
I use cork gaskets & always put them on DRY. Whatever type you use theres a couple of things, If it's a stamped steel valve cover, make sure it is absolutley clean & straight where the gasket rests, typically over the years these covers get over torqued & the rails are bent all to hell. If you get the rails straight, clean & you don't over-tighten the bolts, they should seal up for years & years with no trouble.
 
When fitting a rubber or cork rocker cover gasket ( pressed steel cover), make sure it's clean and dry ( as is the cyl head too), apply Contact Cement to cover and gasket ( the side that goes to the cover),
and stick it to the cover, wait 20 mins, then fit the cover to the head, dry.
The reason for using Contact Cement is to stop the gasket from sliding/squeezing out under pressure, same as having the cyl head clean and dry too.
Contact Cement isn't affected by oil.
 
Partly depends on the type of valve cover you have. If you use covers with a flat bottom surface without the outer lip to contain the gasket using a rubber gasket is like trying to pick up jello... I find the rubber impregnated cork gaskets work the best for me - and they are cheap. I use a very thin layer of sealer on the valve cover side just to hold the gasket (let it set up good with the gasket on before putting on the heads), and hand tight plus ~ a quarter turn to start. Let it set over night and put ~ another 1/8 a turn on before running the motor. This method finally has my current RB with Indy heads dry for the first time since I bought it 3+ years ago - and I think I have tried every gasket/combo on the market..
 
hypermite said:
I use cork gaskets & always put them on DRY. Whatever type you use theres a couple of things, If it's a stamped steel valve cover, make sure it is absolutley clean & straight where the gasket rests, typically over the years these covers get over torqued & the rails are bent all to hell. If you get the rails straight, clean & you don't over-tighten the bolts, they should seal up for years & years with no trouble.
Click to expand...

X2...cork!!
 
When ever its time for a new valve cover gasket on my slant 6 Valiant daily driver. I take great care to ensure a clean/oil free head surface and a clean/oil free valve cover surface. I also make sure non of the valve cover holes are dimpled in from over tightening. I use a dolly or the edge of a steel work table to hammer those surfaces straight. I then will use very thin bead black rtv on the valve cover to effectively glue the Cork gasket to it. I let it sit over night if possible. Then just before I install the VC....I spray a thin layer of engine enamel onto the gasket. Helps to glue the gasket onto the cylinder head and fill any small voids. I hand tighten all the bolts starting with the centers and working out to the edges. Then use a wrench/socket for final tightening but I concentrate on even tightening on all the bolts. They do not need to be very tight. You do not want to deform or cause the gasket to get squished out from between the VC and head. I like the cork gaskets. my 2 cents...hope it helps.
 
Cork or rubber gaskets work.I use Edelbrock Gasgacinch to glue the gasket to the valve cover. Put the adhesive on the cover and gasket,and let it setup for a few minutes. Install the gasket on the valve cover. Flip the VC over and put it on a flat surface with some weight on top. Let it dry,pop it on.

Unless you never plan on taking the VC off again (and even then i wouldnt) never put any kind of sealer on the engine side.
 
I don't remember what I used last time when I put the valve cover on, but when I was trying to get a carburetor to work, the rubber gaskets that come with the rebuild kits and in all of the remanufactured ones I bought wouldn't seal up the gas bowl (Holley 1920). I had to buy cork gaskets from NAPA to get them to stop leaking.
 
Never heard of using contact cement! Might try that sometime. Contact cement is designed to tack up before assembly. So apply and seperate for best results.

I always use 3M "Gorilla Snot" weather strip adhesive. I never glue to the head.

Real pain to try and stick gaskets to the chrome Chinese VC!

Wheel bearing grease on the side that goes to the head. Old VW trick as with them you had to set the valves at every oil change.
 
If you have stock valvetrain I would use the right stuff. It works super good. you don't need gaskits with this stuff. You make a gaskit with this stuff.
 
For a slant-6 I prefer the rubber gasket such as Fel-Pro VS-12680R. Do not use any adhesive, "sealer" or other gunkum on it or you will curse yourself the first time you have to remove the valve cover. Do make sure the cover isn't warped round the bolt holes.
 
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