SBC Guys, have you ever had a leaky valve cover?

I have a brand new crate motor here with leaky valve covers.
They are perimeter bolt and the ones that came on the motor.
Rear outside corners keep leaking oil .
Spun them around, checked for flat, and still leaked.
Changed gaskets once with corks.
Changed them again with felpro permadry gaskets.
Damn thing still leaking.

Thinking I need to tweek that corner and then bolt them back down. I've never had this problem before.

What would you do

 

gotta use spreader bars, or the cast aluminum aftermarket sets.

 

gaskets + silicone rtv top and bottom

 

First thing, if they are steel, peen the bolt holes out. If they are aluminum, or the peening doesn't do the trick, change them....and check out the heads for a defect in the sealing lip.

 

Are you sure it's the valve cover and not the rear intake manifold gasket?

 

Every "tin" SBC valve cover I've ever had leaked when using a gskt [that's over the last 50 years!!"] Only way to be leak-free w/tin covers is silicone or "the right stuff " , pain in the ass to get 'em off but the only way to be leak-free I've ever found.

dave

 

If you use any kind of sealant, be sure to clean the area FIRST with laquer thinner and allow to air dry. Spreader bars, and don't over tighten. Chances are good the covers are chinese, find a nice cheap set at the used parts joint and try them. Are the drain back holes in the head clear? TR

 

I have had to grid down some bad casting bumps/barbs on the head before.

 

I've had good luck with using gasket adhesive on the valve cover only with the thick cork gasket.

 

A bad breathing engine will sometimes blow em out ... the pressure has to go somewhere .... so are you using spreaders? ... maybe I missed a answer.

 

don't over tighten them, turn over and peen the bolt holes back to outside, make sure gasket is siliconed to valve cover only

 

Whichever type of snot you use to glue it to the valve cover, make sure it's dried before installing. Uncured silocone can let the gasket slide out of position. Use the spreader bars and don't over tighten.

 

Thanks guys

These VC are tin, brand new, and came with the engine and I agree most likely Chinese.
They came with spreaders about 1.25" long. The permadry gaskets had 2.75" long spreaders and those longer ones are what's on there now.
Both sets of corks were rtved to the VC, the "Felpro Permadry" gaskets say " do not use any sealer"
There may be a casting flaw back there, its brand new with no history so who knows.

Like I said this is the first one I've ever had trouble with.

The intake manifold isn't leaking, there is no oil any higher than the rear outside corner of the heads and coming directly from there. Oil out of the intake would take a path around the backside of the head and down the block. It's brand new so there is no mistake there.

The crankcase is vented properly and that system is working as it should.

 

Hang tight a minute Newt, your problems sounds to me like you have too much crankcase pressure and it's forcing the oil out the weakest spot on the cover. My question to you, do you have a PVC valve on this engine?
I put together a fresh 350 for my 41 and promptly noticed oil coming out the dip stick tube and valve covers. Pulled the cap off the valve cover and the crankcase pressure was too much, (remember fresh rings, not seated yet), short story, long version, I didn't have a PCV hose hooked up. Promptly installed the correct PCV valve and hose, seated the rings, and no more oil slobbering out the covers and dip stick tube.

 

Yep, pcv installed & works well. PLUS another vent tube out of the other VC right into air cleaner housing. There is no oil flying out of that tube nor excessive pressure- or out the dip stick. Just leaking at the lowest part of the heads were its gathering to drain back to the pan.

Maybe there's too much oil getting to the top end ? Idk
perhaps its not draining back fast enough ? ? ?
The non verified dash guage claims 55 psi at idle. Old motor had 25 psi so the gauge works relatively.

 

Have you had the heads off? Eveb if you have not, check the area between where the head gasket stops, and the intake manifold. Most head gaskets do not extend all the way to the intake gasket. This leaves a gap between the head and the block and gives the valley a clear shot to the area under the head and below the intake. Just something else tp check.

 

Only when there's oil in it.....

 

LoL
Yea, but this is a bad leak.

 

Try thicker cork gaskets and don't tighten them down too hard.

 

If, it's leaky valve covers this is a full proof way to stop leaks. I've used this method a long time with great success.

1. Gasket seal the cork gasket to the valve cover.

2. Run a bead of RTV high temperature silicone around the cork gasket, set aside and let the silicone dry tell you can touch it without any coming off on your fingers.

3. Clean heads with lacquer thinner.

4. Place valve cover on heads and tighten the bolts slowly moving in a figure eight pattern tell snug, don't over tighten.

There will be no leaking in this method but they will be hard to remove.

CRUISER

 

+1 on this one. Everything clean and flat (because if it is you won't have a leak), use rubber cement to glue the cork gasket to the valve cover. Once they're glued on firm install (with spreaders) and correctly and carefully torque the bolts in multiple steps.

Other than at the ends of the intake manifold, silicone sealant is a crutch for poor parts quality, poor parts fit or poor assembly techniques and a lack of patience or knowledge.....not necessarily in that order.

 

Have you checked to make sure your hold down bolts aren't bottoming out on the heads. You said it was a crate engine . Just another thing to check

 

Racers trick was to use Corvair valve cover hold down brackets, they spread the load at each bolt hole. I use GMSC (general motors sealing compound) a brown goo used at the factory for seals and gaskets. My y-block has it on all gaskets.

 

I've had that problem in the past and the only gaskets that worked for me were the MOROSO gaskets. I don't remember the part number, but what I do remember, they were expensive. Never had another problem even after pulling the valve covers off several times to check the valve lash.

 

Peening, (whether it needs it or not).
Spreader washers
Check the bolts to make sure the threads go all the way to the head of the bolt. Clean with lacquer thinner
Use a minute amount of sealer,....and check the intake manifold gasket.

(I guess I coulda just said; "All of the above.")

 

I use Corvair spreaders on all my steel rocker covers. If they are new steel covers they are probably real thin Chinese covers, or Taiwanese maybe. No doubt tweeking the corners may help but you can get a set of corvair spreaders (we used to call them hold down) cheap.


I am actually thinking of casting some perimeter hold downs for using with stamped covers. My old Harley pan head had a cast holdown that went all the wat around the outside of the pan, they never leaked and I had several bolt holes stripped out on my first set of heads.

Oh one other thing getting back to the chevy rocker covers, I buy the cheap summit rubber gaskets, that have a steel shim in them and work real well. They are probably either felpro rubber gaskets in a different box or off shore copies. The only problem I have ever had with them is that they get hard after 3 or 4 years and need to be replaced.

 

I used the "? permaseal gaskets" ( they" have a metal piece sandwiched between a formed lt. blue gasket on both sides.) Just lightly snug down- no problems.

 

I've had great luck using aluminum valve covers with cork gaskets and GM Assembly Adhesive. I make sure when glueing the gasket to the valve cover that everything
fits properly, tweaking as necessary. After the adhesive sets up I fill the crack on the inside with some more adhesive, smoothing it with my finger as I go. This keeps
the oil from sitting in the crack looking for a way out. Pretty much bulletproof.

When I'm ready to put on the valve cover (with gasket attached) I use a single coat
of Permatex Aviation Sealant #80019 on the cork gasket, let it set up for a few minutes and bolt it on.

I have no leaks and the valve cover is removable without tearing the cork. Each time I remove the valve covers I put another coat of the permatex on the cork to reinstall. To remove them the first couple of times all I had to do was put a small block of wood under one corner of the cover and tap it a couple of times with a hammer...........and the cover popped right off with the gasket intact. But, the last time I did it I had to put the car on a lift and use a long piece of oak flooring from underneath along with a bigger hammer to accomplish the same task. But, the cork gasket was still intact.

I'm sure my method will work with steel covers and spreaders.

Merry Christmas!

 

I have used these on problem jobs, they seem to do the trick.

 

On tin covers I use thick cork gaskets and Corvair hold downs, make sure the bolt holes are not deformed.
Glue the gasket to valve cover with yellow weather strip adhesive and let set.
Then just before you put them on, coat (light coat with your finger) the gasket with RTV silicone.

On aluminum covers, just use RTV silicone. Make sure there is no oil on both mating surfaces, clean with paint reducer and a clean cloth. I like the Permatex Black RTV silicone best.