Negative pressure system

[Aron Gleason]

So after 30 years of running 2 breathers with hoses that run out to the atmosphere i decided to add a pcv valve and oil catch. The in port on the can goes to the pcv valve, and the out port goes to the vacuum port on the carburetor. With a breather and hose running out to the atmosphere on the drivers side my oil leak was worse. I put a breather with the holes on the bottom on and the oil leak didnt leak out nearly as bad just a couple drips. But when I shut it off, there was a small spot of oil on the k member. My question is, should I keep the breather with the holes on the bottom, or get a different setup? Im not going to run a hose to the air cleaner.

 

[PurpleBeeper]

My 2-cents? Fix your oil leak & maybe replace the PCV valve??? You’ve got the catch can installed correctly

 

[pnora]

So after 30 years of running 2 breathers with hoses that run out to the atmosphere i decided to add a pcv valve and oil catch. The in port on the can goes to the pcv valve, and the out port goes to the vacuum port on the carburetor. With a breather and hose running out to the atmosphere on the drivers side my oil leak was worse. I put a breather with the holes on the bottom on and the oil leak didnt leak out nearly as bad just a couple drips. But when I shut it off, there was a small spot of oil on the k member. My question is, should I keep the breather with the holes on the bottom, or get a different setup? Im not going to run a hose to the air cleaner.

How much blow-by do you have? Sounds like you have leaks to fix first. What type of oil catch system did you buy?

 

[Aron Gleason]

My 2-cents? Fix your oil leak & maybe replace the PCV valve??? You’ve got the catch can installed correctly

Thanks. But as I said in my post, I just added the pcv valve.

 

[Aron Gleason]

How much blow-by do you have? Sounds like you have leaks to fix first. What type of oil catch system did you buy?

I got the evil energy oil catch can

 

[gkent]

So it sounds like the pcv is restricting and therefore pressure in the crankcase is building - increasing the leakage.

If all you did was add the pcv I can't say I'm surprised. Have you seen the size of the hole in a pcv? Its easy to see how it would be restrictive compared to what is essentially an "open" system.

 

[pnora]

I got the evil energy oil catch can

Which one? You did not answer my question on blow-by. Does the engine have blow-by?

 

[dvw]

The breather should be the flow path entrance into the crankcase. Then the low pressure area in the intake creates a flow path through a restriction (PCV). The catch can allows droplets of any oil picked up to drop into the can. If the crankcase pressure exceeds the capabilty of the flow path, then pressure will back up being discharged by the breather inlet. This can also be aggravated by insuffcient baffling under the breather. The bottom line is if there is excessive crankcase pressure it will back up and leak.
Doug

 

[Aron Gleason]

Which one? You did not answer my question on blow-by. Does the engine have blow-by?

No blow by. And I have the evil energy baffled catch can 300 ML

 

[Aron Gleason]

The breather should be the flow path entrance into the crankcase. Then the low pressure area in the intake creates a flow path through a restriction (PCV). The catch can allows droplets of any oil picked up to drop into the can. If the crankcase pressure exceeds the capabilty of the flow path, then pressure will back up being discharged by the breather inlet. This can also be aggravated by insuffcient baffling under the breather. The bottom line is if there is excessive crankcase pressure it will back up and leak.
Doug

The leak down between the timing chain cover and oil pan on the passenger side all started after I tore the front of the motor off to replace the cam, lifters and timing chain. Before that, I didnt have any problems with oil leaks when I ran the 2 breathers with hoses that ran out to the atmosphere.

 

[Aron Gleason]

So it sounds like the pcv is restricting and therefore pressure in the crankcase is building - increasing the leakage.

If all you did was add the pcv I can't say I'm surprised. Have you seen the size of the hole in a pcv? Its easy to see how it would be restrictive compared to what is essentially an "open" system.

Before I added the pcv valve my leak between the timing chain cover and oil pan on the passenger side was bad enough to where i can watch oil seeping out. After putting the pcv valve and oil catch can with the breather on the drivers side the leak slowed down. So how can pressure be building up if the leak slowed down? Enlighten me

 

[weedburner]

Crankcase vacuum will reduce oil leaks while the engine is running.

If you put a check ball inside the breather, you end up with vacuum inside the crankcase when the engine is running, which in-turn slows airflow thru the pcv system. Slower airflow is less likely to carry oil into the intake tract. Then if at some point blow-by exceeds the capacity of the pcv valve, the check valve opens up to vent any pressure to the atmosphere.

I put check valves inside my breathers, also move the pcv valve away from the valve cover. With a low-tension ring package on the street, crankcase vacuum fixed my oil consumption problem.

Grant

 

[Aron Gleason]

Crankcase vacuum will reduce oil leaks while the engine is running.

If you put a check ball inside the breather, you end up with vacuum inside the crankcase when the engine is running, which in-turn slows airflow thru the pcv system. Slower airflow is less likely to carry oil into the intake tract. Then if at some point blow-by exceeds the capacity of the pcv valve, the check valve opens up to vent any pressure to the atmosphere.

I put check valves inside my breathers, also move the pcv valve away from the valve cover. With a low-tension ring package on the street, crankcase vacuum fixed my oil consumption problem.

Grant

If the pcv valve is moved away from the valve cover, where would i put it? And this might be a dumb question. But how can I add a check ball into the breather?

 

[dvw]

Crankcase vacuum will reduce oil leaks while the engine is running.

If you put a check ball inside the breather, you end up with vacuum inside the crankcase when the engine is running, which in-turn slows airflow thru the pcv system. Slower airflow is less likely to carry oil into the intake tract. Then if at some point blow-by exceeds the capacity of the pcv valve, the check valve opens up to vent any pressure to the atmosphere.

I put check valves inside my breathers, also move the pcv valve away from the valve cover. With a low-tension ring package on the street, crankcase vacuum fixed my oil consumption problem.

Grant

Why would moving the pcv location have an effect on anything? Unless an engine has very little blowby restricting the flow just defeats the purpose. Creating a zig zag path through the breather for oil droplets will reduce oil in the system. A piece of rolled up scotch brite in the breather provides a very effective baffle.
Doug

 

[weedburner]

If the pcv valve is moved away from the valve cover, where would i put it? And this might be a dumb question. But how can I add a check ball into the breather?

Can you move the pcv valve to the top of the separator can?

For the check valves, I used viton rubber balls and machined some push-in ball seat inserts from Delrin that fit inside my K&N style breathers.

Grant

 

[Aron Gleason]

This is the oil catch can im using?

 

[weedburner]

Why would moving the pcv location have an effect on anything? Unless an engine has very little blowby restricting the flow just defeats the purpose. Creating a zig zag path through the breather for oil droplets will reduce oil in the system. A piece of rolled up scotch brite in the breather provides a very effective baffle.
Doug

Moving the pcv valve to a remote location gives any mist a longer path to fall out of suspension.
Restricting flow slows velocity, so more time to fall out of suspension.

Grant