Thread: Leaking SBC valve covers

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Boy, is this an old story! Well I have been around a few years and owned and worked on a lot of different cars and airplanes, being an aircraft mechanic/inspector by trade, but I have never quite understood the thinking behind just four bolts for securing the valve covers on a SBC. Oh sure the four bolts will secure the valve covers, but providing sufficient equal tension to provide an effective, long lasting seal between head and valve cover??? I am sure someone on this forum has discovered the magic answer as to providing an effective seal. I have the newest, expensive gaskets Felpro makes on my engine now and they leak. If someone here has the secret to providing a long lasting effective seal for SBC valve covers I would be ever so grateful. The secret, I know lies in the correct gasket, gasket sealer, correct torque and do not disturb, but what is the most effective gasket and gasket sealer? I have the cast aluminum valve covers and stock heads.

Until I got to your last sentence I figured you had warped, stamped steel covers. Now, I would suggest that you may have poor quality, cast aluminum covers. And assuming you're getting your leakage around the bottom of the cover.

You are correct about proper torque, i.e. not very much. I like the viton gasket material (most people call it rubber though it's not) with metal core. If you need to keep the covers you have then you may need to put a bead of RTV on the aluminum side since that's where the distortion is. Also, next time they need replacement, you can scrape the sealant off the car instead of having all the little pieces going into the engine.

I use Fel Pro gaskets as well with RTV sealant on the block or head side and that is it. Like Denny said, you cannot tighten a cork gasket much at all. 3 ft lbs the most IMO. I do mine hand tight and then half a turn around. Just gotta feel it out. When using RTV put it on the head side, let it sit for 5 minutes or so, then put the gasket and valve cover on and tighten it down but not all the way yet. Let it sit and dry and then tighten where needed. Do what Denny said and start it, get it hot, drive it around and the bolts or whatever should be a tad loose again, tighten. Do that a few times and it should all be good. At least this is what I do and don't ever have problems unless I use those cheap crappy rubber kind of gaskets with that metal in the middle.

You sound like you 1/2 way know how to put valve cover gaskets on. Every cover leak I ever had the gasket had slipped out or you could see a reason for it. If after about the 3 rd. time it was time to look for something else. There is no pressure or standing oil in the cover so it shouldn't be hard to seal. I'd be looking for stopped up return holes, crack in the cover or a stopped up breather.

Originally posted by DennyW
Absolutely Mike, I didn't think of it in those thoughts, but yes, if he keeps getting a leak, more than likely, what you said is the problem.

I've seen some rough looking gaskets that didn't leak. it could be the intake or oil pressure sw. leak.

Well, these are brand new Billett Specialties valve covers and I used these $60.00 Felpro gaskets. Everything seemed OK at first, but after about 6 months they started to leak, just on the left side at the rear. Felpro says not to use any sealer on these gaskets. They are the the metal impregnated silicone rubber gaskets. It just seems a bad design that has been an enormous headache over the years for operators of SBC engines that has required of mechanics to try and come up with an ingenious way of trying to prevent them from leaking. It really seems as though from a design point, a few more bolts evenly spaced around the perimeter and there would be no need to even be concerned about leaks.

I wipe the sealing surfaces down with lacquer thinner and a clean rag. I then put a thin layer of silicone on my valve cover and attach the gasket (rubber or cork doesn't matter, personally like cork). Let the silicone cure overnight. Then I attach the cover to the motor dry-No Sealant! My covers do not leak for several years and you can take them off and on without replacing the gaskets many times. This process works on pan gaskets too.

3M makes a product called "Super Trim Adhesive" (commonly called Gorilla Snot in the business) that I've used on stamped and aluminum covers, and rarely get a leak. I have assembled entire engines with it, and the stuff holds like, well, Gorilla Snot. It isn't made for this application, but I read years ago some top engine builders use it, and I see why. Coat both sides of whatever gasket you choose, and even cheaper ones should hold.

My second favorite is Permatex Hylomar (spelling?) It holds well, and comes apart easily down the road.

You can also go to Autozone and pickup a set of valve cover spreader bars i.e. pressure displacement bars. I put them on my SBC when I installed new gaskets. I did not use any sealer at all and have 600 leak free miles. As the guys mentioned above the trick is to not overtighten the pressure stems. I will enclose a picture of my engine, you can see the little chrome spreader bars on the valve covers. I hope this helps. Gary

Being that you work around airplanes, you probably know that the rubber impregnated cork gaskets seal the best (most aircraft gaskets are made of this material). Dope it up real good with aviation formagasket and tighten it down with the biggest valve cover spreaders you can get and you'll be good to go. Cast valve covers are also less prone to the warping that causes the sheet metal covers to leak.

I've put gaskets on cars and they would come back in awhile leaking and find the gaskets had settled down and all it needed was retighten. tighten them down and never see the car again.

I appreciate all the responses, got some good ideas, I'm gonna get a set of the spreader bars and give that a shot. Over the years I have used a lot of different gaskets and sealers, just never hit on the right combination. I was kinda venting my disappointment with the design, it seems as though the primary concern when installing valve covers is how am I going to prevent these things from leaking. My thought is, the design should have taken into consideration the potential for leaks. It's the same with the intake manifold fore and aft ends, and thats a whole nother story. Thanks again guys.

Originally posted by Hidebinder
I appreciate all the responses, got some good ideas, I'm gonna get a set of the spreader bars and give that a shot. Over the years I have used a lot of different gaskets and sealers, just never hit on the right combination. I was kinda venting my disappointment with the design, it seems as though the primary concern when installing valve covers is how am I going to prevent these things from leaking. My thought is, the design should have taken into consideration the potential for leaks. It's the same with the intake manifold fore and aft ends, and thats a whole nother story. Thanks again guys.

after you get them on and the correct torque on them, drive it a few 100 miles or after you get it hot a few times, then retorque then again. it will help.

In reply to the leaking valve covers. Just recently changed intake and camshaft on my old bucket T. I didn't have a bit of problem beforehand. I've built MANY engines and had to learn the "tricks" on sealing of covers to heads and it's been a long time since I even saw any seepage. I installed the valve covers lastly and was surprised to see leakage.The problem was the covers touched the intake and wouldn't let the gasket seal accept much torque at top of the head.
Nothing that a file didn't take off, I cut .050 or.060 off .Factory defect? I don't know. Dry as a bone now. Good luck & God Bless all the readers................

I run Fords, they've got enough bolts in the valve covers to prevent leaks!!!!!!