LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Crankcase pressure....

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Old Jul 5, 2005 | 11:17 PM
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Crankcase pressure....

is it normal to have oil come up the tube which is attached from the passenger side valve cover to the throttle body? I seem to have this issue....where its evident that oil does reach the throttle body when hose is remooved
Old Jul 5, 2005 | 11:26 PM
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Re: Crankcase pressure....

Exactly how much?
Old Jul 5, 2005 | 11:31 PM
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Re: Crankcase pressure....

well, not much really, but the point is that it does make it to the throttle body....not sure if this is normal or not..
Old Jul 6, 2005 | 05:37 AM
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Re: Crankcase pressure....

It's common. You can use a one way filter like I did on mine. Been working good for me. Pics and part number in my sig pics.

JD
Old Jul 6, 2005 | 12:08 PM
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Re: Crankcase pressure....

I have a filter that I purchase from autozone that plugs into the hole on the passenger side valve cover......but now the probem is that oil comes up this filter and drips down the valve cover and onto my headers...what filter do you use?
Old Jul 6, 2005 | 01:49 PM
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Re: Crankcase pressure....

There's going to be a little backflow through the line to the TB at WOT. That's when you get the most blowby and that's when there's no vacuum on the PCV valve to help evacuate the crankcase. But the oil accumulation should be minimal. Heavy accumulation may be the sign of a plugged PCV valve or excessive blowby.

Pull the top cover plate off the TB and see if there's a puddle of oil in there. If there is, replace the cover plate. With the engine idling, pull the oil fill cap off and hold your hand over it, feeling for air rushing out, maybe in little "puffs".... might be a sign of blowby.
Old Jul 6, 2005 | 02:56 PM
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Re: Crankcase pressure....

Deutsch Oil Seperator Breather:BF412; mounts in the valve cover grommet and may help reduce oil travelling to the TB.
Old Jul 6, 2005 | 03:26 PM
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Re: Crankcase pressure....

Originally Posted by OBE1 95Z28
Deutsch Oil Seperator Breather:BF412; mounts in the valve cover grommet and may help reduce oil travelling to the TB.
I have this filter and the issue is that the oil now seems to be coming out of this hole where the filter in plugged into the valve cover. I am questioning why the crankcase pressure is so high, I definately dont get blowbuy or else I would see it when the car would be at idle.
Old Jul 6, 2005 | 07:28 PM
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Re: Crankcase pressure....

Originally Posted by Hawk350
I have this filter and the issue is that the oil now seems to be coming out of this hole where the filter in plugged into the valve cover. I am questioning why the crankcase pressure is so high, I definately dont get blowbuy or else I would see it when the car would be at idle.

IF it is blowing oil out the v cover that has a filter in it ya got blowby or a bad PCV valve.
Old Jul 7, 2005 | 12:41 PM
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Re: Crankcase pressure....

I just dont understand how it can be blowby, when the cam installed took place, all looked good, cylinder walls smooth, car has 30k on it....I dont abuse it....pvc valve is new.....I put the original elbow fitting back into the valve cover and no oil leak....however I am not sure whether that vacume hose should be allowing oil to pass through it.
Old Jul 7, 2005 | 12:53 PM
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Re: Crankcase pressure....

The line from the throttle body to the passenger valve cover is supposed to flow filtered, MAF measured air into the valve cover, so the PCV valve can pull it out from the lifter valley, sweeping the crankcase vapors out.

It isn't supposed to flow crankcase vapors from the valve cover to the throttle body. As I pointed out in my first response, there are occasions when there is "normal" blowby, and no vacuum, and some vapor will flow backward from the valve cover to the throttle body. It may entrain small quantities of oil mist, and it shows up in the line, the TB, etc.

So far.... everthing normal.

But what you are describing isn't normal. You are blowing so much vapor out the line from the valve cover that its flooding the little filter you put on there, and dripping out on the valve cover, if I understand your description properly - correct me if I read it wrong.

Did you by any chance remove the little baffle plate that is on the inside of the valve cover to make room for roller rockers?

If not, something is forcing excessive amounts of vapor out of the crankcase. Blowby is one possibility - did you pull the oil fill cap off and check as I had sugested?

What other ways could large amounts of "vapor" be in the crankcase? Excess fuel flowing into the crankcase would be a remote possibility... when it hits the hot oil, a lot of it may vaporize and overload the vent system. Or.... water in the oil, which heats up, boils off and leaves water vapor to blow out of the crankcase.

You have to find why the system is either A) not removing the normal amount of vapor, or B) generating excess vapor that overloads the PCV system.
Old Jul 7, 2005 | 01:09 PM
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Re: Crankcase pressure....

Originally Posted by Injuneer
The line from the throttle body to the passenger valve cover is supposed to flow filtered, MAF measured air into the valve cover, so the PCV valve can pull it out from the lifter valley, sweeping the crankcase vapors out.

It isn't supposed to flow crankcase vapors from the valve cover to the throttle body. As I pointed out in my first response, there are occasions when there is "normal" blowby, and no vacuum, and some vapor will flow backward from the valve cover to the throttle body. It may entrain small quantities of oil mist, and it shows up in the line, the TB, etc.

So far.... everthing normal.

But what you are describing isn't normal. You are blowing so much vapor out the line from the valve cover that its flooding the little filter you put on there, and dripping out on the valve cover, if I understand your description properly - correct me if I read it wrong.

Did you by any chance remove the little baffle plate that is on the inside of the valve cover to make room for roller rockers?

If not, something is forcing excessive amounts of vapor out of the crankcase. Blowby is one possibility - did you pull the oil fill cap off and check as I had sugested?

What other ways could large amounts of "vapor" be in the crankcase? Excess fuel flowing into the crankcase would be a remote possibility... when it hits the hot oil, a lot of it may vaporize and overload the vent system. Or.... water in the oil, which heats up, boils off and leaves water vapor to blow out of the crankcase.

You have to find why the system is either A) not removing the normal amount of vapor, or B) generating excess vapor that overloads the PCV system.

DITTO

The oil in the factory line to the TB is NOT blown but sucked into the TB by the vacuum created at WOT through the fresh air intake.As the air rushes by the tube it SUCKS the fumes or oil into the intake.
If the breather ya have on the cover is leaking then the only way it leaks is base pressure blowing(not splash) it into the filter and leaking out.
There is no sense in saying it isn't blow by when a leak down test will tell ya. DO THE TEST(compression test won't tell ya). If it checks out then look for WHY the base pressure is so high.
Old Jul 7, 2005 | 01:22 PM
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Re: Crankcase pressure....

Another quick thought.... excessive vacuum in the inlet duct due to a clogged air filter will make the problem worse.

Otherwise, the port on the throttle boyd is in front of the blades.
Old Jul 7, 2005 | 01:34 PM
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Re: Crankcase pressure....

I did the test where you remove the oil fill plug and put your hand over the hole to see if there is air coming out.....well, there was no air pushing out, it was like normal....what about the throttle body gasket that is under neather the tb? That holds the tb together? Could that be an issue?
Old Jul 7, 2005 | 02:26 PM
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Re: Crankcase pressure....

Getting an oil catch can also help you a great deal...



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