Crankcase breathing

Engine, Trans & Driveline

  1. doublekrossd

    doublekrossd Well-Known Member

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    So the new motor build a significant amount of crankcase pressure when I really get on it. I'm changing my valve covers in order to get push in breathers, current ones are twist in mopar cast. I'm was told I should run a pcv system on it with 2 breathers. It has an Indy valley pan with a removable center in it and I was kinda thinning about running the vacuum to that and then into a catch can, then into a port just under the carb in the back of the intake.

    What say the pros?
    Would there be an advantage or just a mess?
    The motor itself is kind of a radical by some standards street driven monster. Pulls next to no vacuum, pretty "cammy", and will hit 7500rpms pretty quickly. If it was a track car I'd run a header evac system and forget about it but its got a full exhaust and is 95%street driven.
     
  2. oldbee

    oldbee FBBO Gold Member FBBO Gold Member

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    Not an old xpert but google adjustable pcv valves. I think ur between a rock & a hard place.
     
  3. doublekrossd

    doublekrossd Well-Known Member

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    Yep, I'm aware of the adjustable pcv's. I guess I'm not sure if I want pcv or just a full on vacuum hose set in there. I'm guessing both will mess with my carb settings a bit...
     
  4. oldbee

    oldbee FBBO Gold Member FBBO Gold Member

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    For sure, wait there'll be more posts.Another thought is why no vacuum?
     
  5. doublekrossd

    doublekrossd Well-Known Member

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    Pretty huge cam
     
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    • 493 Mike

      493 Mike FBBO Gold Member FBBO Gold Member

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      I'd say that a PCV valve in the valley and one breather on each valve cover would keep up with your blow by. The valley grommet should be located away from any slinging oil source, possibly a baffled device could be fabricated/improvised.
      You might want to perform a cylinder leak down test to confirm ring seal.
      Mike
       
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      • doublekrossd

        doublekrossd Well-Known Member

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        I ordered the M/E Wagner adjustable pcv today. I'm anxious to see if it really works. Still not completely sure if I'll put it in the valley cover or valve cover since the valve covers will have a breather in each one and I think it will just pull air from the breathers too easy.
         
      • Wietse

        Wietse FBBO Gold Member FBBO Gold Member

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        Does a pcv not maintain a certain crankcase pressure?
        I am running just a breather on each valve cover and no pcv valve.
         
      • doublekrossd

        doublekrossd Well-Known Member

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        I think it should maintain more of a light vacuum as opposed to pressure.
         
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        • 747mopar

          747mopar FBBO Gold Member FBBO Gold Member

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          The PCV acts as a check valve to prevent backfires from entering the motor. I run a PCV valve connected to the back of the carb on one side and a breather on the opposite valve cover. As mentioned a baffle under the PCV helps eliminate oil from getting into the valve, most valve covers have this already.
           
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          • rrTor-Red

            rrTor-Red FBBO Gold Member FBBO Gold Member

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          • 747mopar

            747mopar FBBO Gold Member FBBO Gold Member

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            No it's only a check valve. Running a PCV (positive crankcase ventilation) will minimize leaks by maintaining a vacuum instead of pressure building which pushes on seals and gaskets. Also by pulling fresh air in (The vacuum pulls air in from the opposing valve cover) it allows fumes and moisture to be drawn out preventing sludge buildup.
             
          • lewtot184

            lewtot184 FBBO Gold Member FBBO Gold Member

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            will a pcv work well with a large cam and low vacuum? pcv's need baffling even when installed in a valve cover. you might look at the material inside the breathers. maybe it's restrictive. i think a leak down test is in order.
             
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            • Cranky

              Cranky Moderator Staff Member FBBO Gold Member

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              What rpm do you run at the most and how restrictive are your mufflers? 'Healthy' engines do provide a good deal of flow in the headers and a header evac system may do what you need. Another option might be using a vac pump. They will usually increase usable horsepower too. Keep in mind that high crankcase pressures robs hp...
               
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              • doublekrossd

                doublekrossd Well-Known Member

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                The car will cruise normally above 2k, highway obviously more. The motor is brand new but i suppose I'll do a leak down just to see if I don't have a funky ring. The exhaust is a complete tti system with upgraded dynomax ultra flows and 3"all the way out
                 
              • doublekrossd

                doublekrossd Well-Known Member

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                Well, I finally got everything installed with the M/E Wagner adjustable pcv. It's got me a little nervous about introducing too much air into the induction now. I set it up as instructed, drive it around for a bit and now the idle is high, almost like a vacuum leak. I know there's going to be some adjustment, it doesn't seem lean anywhere as its running very strong and responsive throughout the rpm range but the last thing I want to do is lean it out. Also it doesn't seem to be leaking as bad, but I haven't replaced seals that were leaking previously to adding the pcv yet...
                 
              • beanhead

                beanhead Well-Known Member FBBO Gold Member

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                I had the same problem... a few seeps only after drives with higher RPM blasts (I have a melling high-pressure oil pump).. I use a breather on one side and PCV on the other. I took the breather off to see how it 'breathed' and I noticed it was very restrictive (the kind that looks like a little filter element) I replaced it with the chrome stock-style and that has helped..full throttle=no vacuum=pcv stops sucking momemtarily. I may even add a 2nd breather...
                 
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