Help With PCV System

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  1. #1

    Default Help With PCV System

    I am building a 03/04 cobra engine. 05 Aluminator block, kenne bell 3.2 blower. It is being swapped into a crown victoria. The problem I am having is I don't have an existing motor to look at to reference in my build process. I have pretty much everything figured out, and most of the accessory drive parts etc already. The one thing that keeps stumping me is the PCV system. I know there is the port on the bottom of the lower intake assembly, then there are the two ports on either valve cover. From my understanding, I should tee together both valve covers, then place a check valve in-line, run to a non-vented catch can, then to a vacuum source.

    Now my question is, what should I do with the port on the bottom of the lower intake? How should this be plumbed into the PCV system?

    If anyone could help me out with this, that would be great!

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  3. #2

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    There are pics and some Ford diagrams in my build thread. That port runs to a tee with one end on the back of the blower, the other to the PCV.

    Alll in here: https://www.modularfords.com/threads...r-Gibtec-Build

    Edit: This is on my website, may have left it out of the build thread (but plenty of pics there in any case):

    Last edited by jrgoffin; 03-03-2019 at 09:04 AM.

  4. #3

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    Thank you! That diagram is extremely helpful! What about the left bank of the engine? How is that side of the pcv system plumbed?

    What I do not understand, and this is most likely ignorance on my part, but how does the system compensate (or does it not?) for essentially a boost leak being plumbed into the PCV system?



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  6. #4
    Senior Member Array 04DeadShort's Avatar
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    The left bank (passenger side) is the air into the engine. From the factory it a hose from the cam cover to the intake tube, between the mass air sensor and throttle body. Here is a old pic of mine for reference.

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  7. #5
    Senior Member Array soap's Avatar
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    Quote Originally Posted by rainyp71 View Post
    What I do not understand, and this is most likely ignorance on my part, but how does the system compensate (or does it not?) for essentially a boost leak being plumbed into the PCV system?
    Not really sure what you are asking here. The PCV system should never see boost, the port on the backside of the blower (as seen above) is only vacuum.

    --Joe

  8. #6

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    Quote Originally Posted by soap View Post
    Not really sure what you are asking here. The PCV system should never see boost, the port on the backside of the blower (as seen above) is only vacuum.

    --Joe
    That's what confusing me. But there is a connection on the bottom of the intake which is plumbed into the PCV system in the above diagram. The connection on the valve cover doesn't matter because it has the pcv valve not allowing positive pressure into the crank case, but it is tee'd into the back of the blower as well.

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  9. #7

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    Quote Originally Posted by 04DeadShort View Post
    The left bank (passenger side) is the air into the engine. From the factory it a hose from the cam cover to the intake tube, between the mass air sensor and throttle body. Here is a old pic of mine for reference.

    Sent from my SM-S767VL using Tapatalk
    That is perfect, thank you!

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  10. #8

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    Plug the hole at the bottom of the lower intake and run both valve cover vents to a vented catch can, I do this to all my builds and customer builds.

  11. #9

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    Not having a functioning PCV system decreases ring seal as it removes the possibility of negative pressure in the crank case. I could be wrong though.

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  12. #10

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    I am fairly confident I now fully understand the PCV system function on the cobra. However I am tired and already overtime this week so I will get back to this tomorrow and explain everything and everyone can chime in if they see any issues. I want to make sure this is documented for anyone else who is looking for PCV info.

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  13. #11

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    The PCV system is not complicated, yet so many people screw them up with all the add-on's. I will say that a good oil separator is a must, but you can get nice billet versions off eBay for around $50 that work very well.

    Section from my site on them: http://www.terminator-cobra.com/engi...#Oil_separator

    Basic PCV diagram (oil separator spliced in where "intake vacuum" is circled):



    All in action:


  14. #12

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    Quote Originally Posted by rainyp71 View Post
    Not having a functioning PCV system decreases ring seal as it removes the possibility of negative pressure in the crank case. I could be wrong though.

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    A factory PCV system can in no way shape or form impart a significant enough of vacuum on the crank case to be beneficial, a actual vacuum pump can and does help with ring sealing though. PCV systems oil the intake manifold and the oil mixed in with the air/fuel charge is not good for the combustion process, the data is out there do some research on it.

  15. #13

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    Ideal PCV setup
    Attached Images Attached Images  

  16. #14
    Senior Member Array 04DeadShort's Avatar
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    Here is my current setup. I did the wire tuck mod and mounted a UPR universal oil separator on the fenderwell. Works well for me.

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  17. #15

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    Joe's drawing (below) is a good illustration of the various parts of the integrated engine / pcv system.
    Name:  PCV.jpg
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    It is worthwhile to remember that the pressure in the crankcase comes from blowby, which is combustion gases which leak by the ring package creating a positive pressure in the crankcase. The crankcase positive pressure is exhausted into the engine intake through the PCV valve at the rear of the driverside valve cover and also what Ford calls the crankcase vent tube at the front of the passenger side valve cover (see pic below)
    Name:  Vent Tube.png
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    The vent tube assembly provides a similar route for the blowby gasses in the crankcase to be reintroduced back into the engine. Because the gaseous component of the blowby gases has already been metered through the MAF it is introduced post MAF. The intake plumbing in front of the throttle blade and behind the MAF has a very small pressure drop at any throttle position and engine rpm other than wide open throttle above 6000 rpm. Even at elevated engine speed and WOT conditions the inlet vacuum signal pre throttle and post MAF is not likely to exceed 2 inches of vacuum.

    The low inlet vacuum however is still greater than the higher crankcase pressure from blowby. As a result the crankcase blowby flow is from the crankcase to the inlet runner post MAF and pre throttle. The PCV connection from the driverside cover originally was plumbed into the intake system post blower which means at idle it is exposed to vacuum, establishing a flow direction from crankcase to intake manifold. Under boost the PCV valve prevents the positive manifold pressure from being used to pressurize the crankcase through the PCV plumbing.

    While there can be arguments about the effect of eliminating the PCV system. The removal of the PCV system and the use and maintenance of an air oil separator can mitigate the sludge build up on the supercharger internals, intercooler and underhood area that we so diligently try to keep clean.


    Ed
    Last edited by eschaider; 03-07-2019 at 02:40 PM. Reason: Spelling & Grammar

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