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Opinions on Valve cover Oil breather. Come on in

9856 Views 20 Replies 8 Participants Last post by  6speeder
So after I had the porous block/main seal repair work. My dealership questioned the crankcase pressure. I completely discounted that comment by telling them my PCV tubing, intake plenum were completely dry. I also advised them that I had a catch can installed for approximately 2000 miles and collected not a drop of oil. If the leak were associated with increased crank case pressure, I would have oil in the pcv tubes etc. We agreed on that.

I started to research the pros and cons of a valve cover breather and thought I would try one. I know it will not improve performance but if it will help the existing PCV system reduce pressure, it may be a good thing. I found a Metco breather and installed it along with the existing PCV system. I took a spirited after the install drive and there was no cabin odor, or oil mist collecting on the valve covers and no leak.


Here is the product:

Here is the install photo. I opted to install it in the plastic fill tube although it can also be installed directly into the valve cover.

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A crankcase breather is a bad idea under normal driving conditions. When not under boost the blowby and other vapors in the crankcase are removed by the PCV system. It is a closed system. When you put on a breather you are opening that system and depending on how you reroute the PCV system either are introducing a vacuum leak into your intake (through the breather and the crankcase.) Not good. Or you are completely disabling the PCV system which will allow those caustic vapors to accumulate in the oil. Also not good.
It is my understanding that

When working properly, fresh air should enter the breather and the intake vacuum should pull fumes and smoke (blow-by) through the PCV and re-burn it in the engine.
If all you do is replace the valve cover oil cap with a breather then you are introducing a vacuum leak into the engine. If you have a scanner or access to a Tech II, monitor your LTFT's, then pull the cap and check them again. You will see the LTFT's spike and probably over time get a check engine light. The PCV system uses engine vacuum to pull out contaminants, but it uses air after the MAF, so it is properly metered. With a breather you are introducing non-metered air, a vacuum leak.
Good luck. I went through this with my supercharged Lightning engine AND my Z06 Vette. The stock PCV systems just seem to pull oil mist through the intake. The best I have been able to do is greatly reduce the amount by limiting the PCV airflow. I have tried THREE different catch cans on my Vette, two did nothing to stop the oil flow, the one I"m running now, the Revxtreme "seems" to work as my oil consumption is way, way down, and I don't have oil pooling in my intake manifold anymore.

I tried rerouting the PCV and using a breather which eliminated the engine vacuum in the crankcase. It totally eliminated the oil in the intake problem but with no PCV I'm sure the oil was being contaminated much faster and would need to be changed much too often for my tastes (and pocketbook, Mobil1 is NOT CHEAP).
CBLOVEDAY: I'm sorry, I haven't tried a catch can on the V yet, so I don't know the correct install. I do know the outlet side of the catch can should go to the vacuum source.

I inspected the intercooler when I had the supercharger cover off, at 5,000 miles and it did show some oil was flowing in the intake, but not as bad as my old Lightning engine. As long as my oil consumption is low I am not going to fool with the PCV system on the V, it's way more complicated than on the Vette.:hmm:
If the LSA is like the LS7 (I think it is) then instead of a PCV valve they use a restrictor, or orifice to set the airflow through the system. I think you can see it in your picture, its the fitting on the front of the valley cover facing the passenger head.

Your intercooler looks pretty clean, no visable oil in that shot. That's a good thing.
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