Strange Oil Leak

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OSUcowboy

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Hello all,

I have a 318 with an edelbrock carb and intake that is leaking oil in a very strange way.

The block seems to be pressurizing and as a result is blowing oil out of the dipstick tube and around the valve cover gaskets. If I take the PCV valve out the block does not pressurize and it doesn't leak because the gases can adequately vent. My main concern is with how much gas is there. It seems to me there must be a serious excess if the PCV cannot keep up. If I put my finger over the hole pressure builds pretty quick and when taken off a noticeable whoosh of gas comes out of the hole as the pressure equalizes.

Is this at all normal? Is something seriously wrong?


Thank you in advance
 
check your oil breather i had same problem my filter was clogged and make sure hose from pcv is not clooged all the way to carb
 
iggys68dart said:
check your oil breather i had same problem my filter was clogged and make sure hose from pcv is not clooged all the way to carb
Click to expand...

On a healthy engine the oil breather should spend most of it's time acting as an INTAKE to the crankcase, flowing air into, around the crankcase, and then out the PCV

On engines that typically were getting worn, with breathers linked to the air cleaner bonnet, a tell-tale sign was excessive oil buildup in the air cleaner.

First thing I'd do is make absolutely sure that you have a clear 3/8 hose path to the intake, that is, pull the pcv out of the hose and it should instantly kill the engine unless you have it revved some

Next change the PCV just because they're cheap.

I suspect you have a severe blow-by issue. You may have a cracked piston, broken rings, or the engine is just tired.

This can also be caused by a head gasket blown in "just the right spot"

What is your perception of the engine overall condition? Does it use/ show oil anywhere else like the exhaust.
 
67Dart273 said:
On a healthy engine the oil breather should spend most of it's time acting as an INTAKE to the crankcase, flowing air into, around the crankcase, and then out the PCV

On engines that typically were getting worn, with breathers linked to the air cleaner bonnet, a tell-tale sign was excessive oil buildup in the air cleaner.

First thing I'd do is make absolutely sure that you have a clear 3/8 hose path to the intake, that is, pull the pcv out of the hose and it should instantly kill the engine unless you have it revved some

Next change the PCV just because they're cheap.

I suspect you have a severe blow-by issue. You may have a cracked piston, broken rings, or the engine is just tired.

This can also be caused by a head gasket blown in "just the right spot"

What is your perception of the engine overall condition? Does it use/ show oil anywhere else like the exhaust.
Click to expand...
nice post as my motor is worn i appreciate all the signs you indicated you hit the nail right on the head i was just relating my experience wich is limited thanks looking forward to more of your posts
 
The motor was rebuilt less than 10,000 miles ago. When it was done, new pistons and rings were installed. The head gasket is not blown. I just had the heads off, and everything was fine. I will check to make sure the PCV / hose is clear.

Is it a must to have a breather and PCV valve both? I have just a PCV without a breather. It was my understanding this would work since the PCV would hold the crank under a vacuum.
 
OSUcowboy said:
The motor was rebuilt less than 10,000 miles ago. When it was done, new pistons and rings were installed. The head gasket is not blown. I just had the heads off, and everything was fine. I will check to make sure the PCV / hose is clear.

Is it a must to have a breather and PCV valve both? I have just a PCV without a breather. It was my understanding this would work since the PCV would hold the crank under a vacuum.
Click to expand...

I know of no engine that is set up without two openings into the crankcase. Traditionally, the pcv is one and an open breather linked into the air filter is the way "it was done"

This setup insures that say, under high throttle settings, the PCV may not keep up, and the crankcase may push vapor out the "intake" and into the air filter where it's simply sucked down the carb throat.

Some older cars (early days of PCV) used an open breather. The problem with this is that fumes then are ejected into the "engine room" and can be noticed sometimes, in the cab

I'd say you might have found the problem.
 
Two things,
First, the fact that new pistons and rings were installed means nothing. If the work wasn't done well or the 10K miles had a bit of racing they could be going already creating blowby. A simple test to see would be a leakdown test. But, IMO, the issue is the lack of a breather. As was said, you have to let air into the engine to ventilate the crankcase. The PCV takes the majority of the gasses out but only if you have a source of fresh air to be sucked in. Also, when you are "driving spiritedly" or the rings are wearing, the breather will let pressure the PCV can't deal with entirely escape without puking oil all over.
 
Also as you open the throttle, vacuum drops and the PCV is less effective. Thats why you also need a breather, for those WOT 0 vacuum conditions when the pcv valve now becomes a restriction to the escaping blow by gasses.
 
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