Valve Cover Oil Leaks

[Patrick H.]

Does anyone have any sure-fire way to keep valve covers from leaking? My stock stamped steel covers leaked on my small block 71, so I swapped them for stock aluminum ones with the flanges since the car isn't for judging. I also installed Mr. Gasket Ultra Seal gaskets, which were supposed to "swell" to stop oil leaks, but the covers still leaked significantly. I have tried with and without Permatex black sealant, both between head and gasket and between gasket and cover, and this is no miracle either.

I am sick of cleaning all the oil streaks off my engine, especially since the rest of the motor is so clean. I have better things to do with my time.

Any thoughts?

[John]

Re: Valve Cover Oil Leaks

Check the valve covers with a straightedge to make sure the sealing surfaces are flat for their full length, and use a sealant between the upper side of a swelling cork gasket and the valve cover. If the sealing surfaces are distorted from the screws being over-tightened, they will leak and leak, and the more you tighten them, the worse it will get.

[Patrick H.]

Re: Valve Cover Oil Leaks

I tried this already. They still leak. This is true whether I try to tighten them a little or a lot (but not too much).

They seem to leak more between the head and the gasket, due to the head lip being somewhat "rounded" in profile, and not flat to accept a gasket or to seal well. Is this what others have seen too?

[Mike Ward]

Re: Valve Cover Oil Leaks

I don't think I've ever seen a small block that doesn't leak a little oil now and then. That's why they invented rags, I bet.

Are you sure your PCV valve etc. is OK? If your crankcase is over-pressurizing, this could cause the leakage. Also, if your motor has very high blowby to begin with (due to wear on the rings for example) this might overwhelm the valve.

Mike '73 coupe

[Gene M.]

Re: Valve Cover Oil Leaks

Pat, Assuming both the head surface and the cover are very clean (use disc brake cleaner). As others said the covers must be straight. Glue the new cork gasket to the valve cover with indian glue, it's a brown gooie stuff in a short brown plastic bottle (available at NAPA about a dollar). Let this sit on a glass surface for two days (don't cheat) on it's mounting surface with about five pounds on each one. If you can see daylite between the gasket and the glass the covers were not straight enough to start with. For judging points over spray the gaskets orange on the outside edges. After two days just bolt them on the heads snug, not tight, use a nut driver so you don't over tighten.

[Jack]

Re: Valve Cover Oil Leaks

Assuming originality is of little concern you might try the following for the stamped steel covers. Chevrolet developed and sold 4" long spring load spreaders for the Corvair valve covers which were really leaky little buggers. I have used these on my Corvette in years past.They are at least Genuine Chevrolet!Simplistic and inexpensive. JackNCRS#896

[Patrick H.]

Re: Valve Cover Oil Leaks

The PCV valve is new GM, and the motor was rebuilt 3 years ago/7000 miles ago with Total Seal rings. I don't expect much blowby with these ...

[Patrick H.]

Re: Valve Cover Oil Leaks

I've got 3 sets of these, but I thought good aluminum covers with the integral flanges would be a better looking option. I still like the look of my original "plain jane" orange covers, but I know those are bent; thus the switch. This motor was restored externally to NCRS standards, and switching the covers was my first "deviation," but as they are correct Corvette, and it isn't judged, I wasn't so concerned.

[Joe L.]

Re: Valve Cover Oil Leaks

Oil leakage from small block valve covers is a notorious problem of long-standing. Chevrolet seemingly ignored this problem for many years as evidenced by the fact that the valve cover sealing system remained essentially unchanged from the first 1955 265 cid until the early eighties 350. At about that time GM made significant improvements to all of the small blocks leak areas. This included the rear seal, oil pan gasket, and valve covers. For the valve covers, the head mating surface became a MACHINED surface in contrast to the rough cast, "rounded" surface of old. Also, center bolt valve covers which avoid the flange distortion of the perimeter style covers became standard. Lastly, an improved silicone rubber type gasket came into use. All these things helped a lot, but even late C4s leak from the valve covers to some degree. In addition, most of the later mods cannot be retroffited to earlier engines without MAJOR changes no respectable restorer would consider.

I have fought this oil leak problem on my original-owner '69 since the day it was new. Very early on, I switched to the cast aluminum Corvette covers, since my 300hp-350 was originally equipped with the stamped steel variety. This helped, somewhat. But, the covers still leaked. I tried every type of gasket and sealer available over the years. Some worked a little better, but the valve covers still leaked.

In the late 1970s, Fel Pro introduced a thick, steel cored, "cork-prene" gasket. I have found this gasket to be the best for sealing and I have used them ever since. They are expensive, but worth it in my opinion. Continued vigilence is still necessary, though. This means that you have to check the tightness of the retaining bolts frequently and you have to replace the gaskets from time-to-time.