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Thread: LS3 PCV Connections

  1. #1
    Tuner in Training
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    Feb 2019
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    VA
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    LS3 PCV Connections

    I've got a crate LS3 (430 HP) with a truck intake and I have a question about routing the PCV hoses. The shop that did the install connected a hose from the intake tube (Airaid Jr.) to the valley cover and another from the Sniper 90mm TB (draws from the MAF side of the throttle blade) to the passenger side valve cover. Well, this doesn't work because both "froms" are drawing from essentially the same place, hence no vacuum to evacuate the crankcase. I have a vacuum gauge connected to the intake manifold on the passenger side. There are no other unused ports.

    Here is my question: Is there any reason I can't tee off the vacuum gauge port for the dirty side return for the PCV? I'm going to install an oil/air separator tomorrow and I want to plumb it in between the valley cover and the vacuum gauge intake port. Is there any reason this won't work?

    What I want to end up with is a hose from the TB to the valve cover for clean air, plug the port in the Airaid tube and plumb the separator between the valley cover and the intake port for the dirty side.

  2. #2
    Tuning Addict blindsquirrel's Avatar
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    Apr 2017
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    If at all possible, I would put fresh air to both valve covers ('tee' in the pre-TB hose is fine). Even the factory systems that are set up with PCV in the valley and fresh air to only one valve cover, one head essentially isolated from the air flow end up with one head filthy and the other relatively clean after some mileage. Circulate the air through as much of the engine as you can.

    Best is probably PCV in one VC, fresh air in the other VC, one at the front other at the back. The valley cover is a poor location for the PCV in my opinion.

  3. #3
    Tuner in Training
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    Thanks, Squirrel. So here's what I've done:

    I was able to find a Gates breather hose at my local O'Reilly's just so I could get the connector that fits into the port in the top of the intake where it's really supposed to be in the first place. That's the dirty return. The other end of that hose goes to the oil/air separator. The other port on the separator goes to the port on the lifter valley. On the clean side I have the port on the TB teed into both valve covers as you suggested. It was easy to do and makes a lot of sense.

    All I have left to do is actually connect the separator. I painted the mounting bracket and need to let it dry overnight. That and it's too dang hot and humid in SW Virginia at the moment to keep working in the garage. When it's all done it will be a very clean install. I just hope it fixes my stalling problem...