Thread: Problems with aluminum valve covers

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This is going to take a minute, so I will get to the point. I have a 388 stroker with about 1000 miles on it. I just finished building it before the winter. I had Edelbrock valve covers on it and they were in pretty bad shape, so when I got the money I bought new Aluminum valve covers. I had a K&N style air breather (open filter style air breather) and never had a problem with it when the Edelbrock valve covers were on. When I put the Aluminum valve covers on, oil would come out of the air breather and leak onto the valve covers. I put the old air breather I had back on (just a Mr. Gasket air breather with a limited hole and closed face, pretty generic) and it seemed to solve my problem.

However, I still seemed to be losing oil. I checked underneath to see if I could see oil leaking from anywhere, including a bad seal on the new valve covers, and to my displeasure, I noticed oil leaking from the back of the oil pan where the main seal is. I am not exactly sure if it leaked from there all the time even when I had my Edelbrock covers on, or if it was just when I had the aluminum ones on. I just think that the aluminum valve covers were causing too much pressure build up in the crank and causing it to clog the air breather, thus making oil spew out in whatever point it could. The PCV valve seems to have good negative pressure (suction), and I even backed it out a little bit in case it was too close to the baffle of the aluminum valve cover.

So, I went to put the Edelbrock valve covers back on to see if it stopped the leaks due to better breathing, and to my displeasure even more, the washer (or retainers, im not exactly sure) underneath the bolt for the rocker arms, I found that 3 of them were cracked. So the car is sitting and I am not using it until I get that fixed, but does anyone have any suggestions as to what could have been causing the oil leaks? Do you think it was the valve covers causing too much pressure? The gasket for the oil pan is a really good one and the main seal is brand new (2 piece). Anyone ever have a problem like this? Any suggestions?

i have`nt looked at a small block chevy in about 100 years but is`nt the oil sending unit right next to the distributor .. it could have started leaking on you and running down the back of the engine .

May be no baffle under the vent hole look at both valve covers from underneath(inside) and compare

I had a leak at the back of the motor one time many years ago (oil on the floor) and was thinkin' it was the rear main seal. After cleaning up the mess and running it while paying attention, I realized that the oil was coming from around the black rubber seal between the bottom of the manifold and the top of the rear china wall. After talking to some buddies, I learned that they didn't use those cheezy, fosdick seals any more. They just squirted a fat bead of silicone across the china wall front and rear and sat the intake manifold down on that. I've been doing it that way ever since.

I think i know what your problem is. Are the new valve covers aluminum, finned, polished and no name brand? Did you buy them off ebay or at. Swap meet? If so...they are chinese knock offs ..the breathers are crap. They have an oring in side that does not seal. The pcv is probably inside the breather. What happens is, oil is pulled up into the breather because there is either no baffle inside the v/c or the one in the cover is a pos...oil puddles inside the breather,after shut thev car off,wait ten minutes and oil runs out of the bottom of the breather. Couple things that can be done...seal the breather so no oil can come out of the bottom,put a restrictor inside the pcv hose...or just save up and buy some usa made breathers/valve covers.

Not to say it can't be leaking from somewhere else, but I am almost positive it is the rear seal. It doesnt seem to be leaking from the distributor or the back of the intake (as it looks strikingly clean). I just know that if you arent getting good enough ventilation out of your air breather, the vaccum pressure will seek out any weak spot or holes it can find, thus pushing out oil. :/

I chased an oil leak on my SBF, and even went to the trouble of pulling the pan and replacing the gasket, thinking it was leaking around the rear main. I finally realized that my oil was coming from 1) the breather caps (no PCV), and 2) the fact that the valve cover only met the mating surface of the aluminum heads about 1/16", and the thick rubber gasket was rolling with torque (a stock FelPro gasket overlapped the top edge of the heads, but the bottom edge of the covers). I replaced the cast covers with a pair of fabricated covers made by the head supplier, and made sure that they had baffles at the ports on both sides. I replaced one breather with a fill plug, and the other with a direct mount PCV. Oil leak solved. The lack of baffle plates was a big part of the problem, but the mismatch in mating surfaces was the killer.