So I finally got fed up with the oil leak on my '70 malibu, and I took her to a mechanic. He said there was too much internal pressure or something, and it caused about 3 seals to blow (including my rear main which is where all the oil's coming from). Anyways, he said I need a new engine, or a complete rebuild. So I asked around and got many differing opinions. One guy said I could buy a device that replaces the oil cap on the valve cover and it relieves internal pressure. Another guy said I just need to buy Indian Head gaskets (or something along those lines) which are guaranteed not to blow out. Any of you guys ever had this problem? I need some expert advice!!!

First of all, if the PCV system was working properly, there shouldn't be any excess crankcase pressure. Are all of the crankcase ventilation components hooked up and functioning? PCV Valve changed with proper part? Did you check the oil return holes on each end of each head? Too much slugde there will prevent the crankcase from "breathing" properly. Remove the PCV valve from the valve cover with the engine running and cover the bottom of the valve with your finger. You should feel a strong suction. If not, disconnect the valve from the hose which should hook to the bottom of the carb and check for vacuum at the end of the hose. If everything is working properly, fresh air should enter the passenger side valve cover and draw out the crankcase vapors from the left hand cover, through the PCV valve and into the carb, to be burned. If you're blowing seals, your PCV system isn't working correctly. Check it out.

[This message has been edited by MalibuJerry350 (edited 02-22-2000).]

Jerry,

I remember the mechanic showing me the finger trick you described. He showed me that there was no suction. The PCV valve actually becomes disconnected from the valve cover. The pressure pushes it out, and I always have to check and make sure it's connected. I haven't checked the rest though.

If you have no suction, there is probably excessive carbon buildup in the intake. You should have manifold vacuum at the pcv valve.

bistledink,
I don't know what kind of carb you have, but if you disconnect the PCV line at the carb base you should have manifold vacuum there. If not, remove the carb and check for sludge buildup in the vacuum port on the carb. This is a very common problem. Don't forget, crankcase vapors pass through here! I have a feeling that's where your problem is. After owning my 70 Malibu got 30 years, a daily driver, there aren't too many problems I haven't seen! http://www.chevelles.com/forum/smile.gif

Ah ha! It seems as though there was a split in the PCV line right next to the carb base. I replaced the hose, and called the mechanic back, but he said it still doesn't explain why there's so much pressure!

Okay the PCV line and valve are fixed, hopefully even runs a little smoother,
Now, about those (3) blown seals, I have seen the lack of pcv cause the front and rear intake manifold gaskets to blow, that's (2),
that rear main seal has nothing to do with pcv system, what is your oil pressure??????
A good/properly installed rear main seal will
generally hold even the highest of pump pressures (I've seen 80 psi with no leaks).
Have you cleaned the motor???????
Is it still leaking???
From where??????

RicksRag
TC #560
ACES #3702

If this is a re-post??????? Sorry!!!!!!!!!

The PCV problem can cause the front/rear intake maanifold gaskets to blow.

The rear main seal sees only pump pressure!!

Have you cleaned the motor ?????

Is it still leaking?????? Where ????????

Kept it brief >>>>>>>>>>>>>>

RicksRag
TC#560
ACES#3702

Again, do you still have the high crankcase pressure? Is this the original engine and how many miles are on it? The crack in the PCV hose shouldn't cause the crankcase pressure to elevate, unless you have an abnormal amount of "blowby" past the rings. And, even then, for the PCV valve to blow out of the valve cover grommet indicates that the breathing is impaired somewhere. On the old '50's small blocks that had a road draft tube as a breather, there was a baffle under the intake manifold that would "sludge up". this would cause so much crankcase pressure that oil would be thrown out of the filler tube! So, that leads me to believe that you should pull the valve covers off, at least and check to see how much "gunk" you have in that engine. If it's a high milage engine that didn't receive frequent oil changes, that could be the problem. The high milage alone isn't the problem, hell, my first 350 went 345,000 miles before she started to smoke, but I changed the oil every 2000 miles since it was new, so the engine stayed pretty clean. Let us know. Good luck! http://www.chevelles.com/forum/smile.gif

I had the same problem before I rebuilt my engine. The engine ran really strong, infact better than it does now after the rebuild, anyway, I had lots of crank case pressure and my PCV system worked fine. I would blow lots of oil out the breather and blew a few seals. I first rebuilt the heads and that sealed up the top end and made my problem worse. Instead of some pressure going thru bad valves it all went to the crankcase. I got so fed up with after blowing almost every seal in my wengine that I finally pulled it and rebuilt.

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ACES member #3339
Owner of 69' Chevelle SS396

RicksRag,

Yep, you got the seals right. I don't really know my oil pressure, unless there's a way to tell on '70 malibu's that I don't know about. The same seals are still leaking.

MalibuJerry,

Yes, the crankcase pressure is still there. It's the original 307. The previous owner said he had the engine rebuilt less than a year ago, but I doubt it. The speedometer says 71,000 miles. Your guess is as good as mine.

Bigyellow,

Yep, that sounds exactly like my prob, and I'll probably end up rebuilding or buying a new engine.