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Do I need my PCV Valve?

Discussion in 'The Garage' started by Topdown, Sep 15, 2003.

  1. Topdown

    Topdown 1/2 ton status

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    Title pretty much says it all. Do I need it? I have been told to simply remove it and run without it. Will I gain/lose performance? Will it seriously alter my vacuum pressure? (I have no vacuum gauge)

    Thanks
    -Ryan
     
  2. Goober

    Goober 1/2 ton status

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    This was covered awhile ago in another post.

    Taking off your PCV system will probably not provide you with any performance benefits but it could be the cause of some really nasty problems.

    Positive Crankcase Ventalation (PCV) is not necessarily a "smog" item. It's necessary for an engine for a few different reasons.

    First, all internal combustion engines have blowby past the piston rings especially when cold. That blowby contains fuel vapors that will mix with your oil. Gasoline is a excellent solvent and will thin your oil out and break it down over time. Thin, broken down oil will not lubricate your engine ..... that's bad.

    Second, the blowby will create a high pressure area inside your crank case that will try to push oil out every gasket and seal. Having a functioning PCV system allows all the fuel vapors and blowby gasses to get removed from your crank case and re-introduced into your combustion chambers to get one more chance to burn. It also creates a low pressure area inside your crank case which will tend to suck oil back into the engine rather than force it out.


    PCV systems are used on everything from regular cars / trucks to Winston Cup cars and Top Fuel Dragsters. They have an important job to do so make sure your PCV system is working properly rather than removing it.




    /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
     
  3. Topdown

    Topdown 1/2 ton status

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    Thanks G!

    I missed it in the 2nd gen forum - read through that post to about 1/2 way and surely learned what I needed/wanted to know.

    I will definitely keep the PCV - and let the guy who told me I dont need it know that he may want to look into it a little more.

    I am curious though, I seem to be sucking in valve cover gaskets... is it possible to have too much PCV vacuum? I cant think of any other reason that I would be sucking them in.

    Thanks
    -Ryan
     
  4. R72K5

    R72K5 Banned

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    i dont knwo how there coul be too much vacuum when factory pcv is connected to straight up engine manifold vacuum source in which is not weak, so is power brake booster also

    also make sure you make a filtered return for air to get back into the crankcase that the pcv sucks out, in stock form this is connected at rear of pass side valve cover and the small filter is attached inside of air cleaner housing
    you have to do something like that with a small filter or youll end up with dirty oil faster than you wish and dirt in oil is a big no-no unless you dont care about the bearings and such being scratched
     
  5. Topdown

    Topdown 1/2 ton status

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    No worries on the filtered return, I splurged when I rebuilt the engine and put a K&N on the air return. So it should be getting plenty of clean return air...

    Beats me, just figured I would ask and see what fell out.
     
  6. Goober

    Goober 1/2 ton status

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    [ QUOTE ]
    is it possible to have too much PCV vacuum? I cant think of any other reason that I would be sucking them in.


    [/ QUOTE ]


    Like R72k5 said, make sure you have a good breather on the opposite valve cover from your PCV.

    With the PCV system sucking all the fumes out of your crankcase and a decent sized breather your crankcase should not see much vacuum at all. The air should flow right through. If you don't have a breather (or yours is plugged, I've seen that happen) then you will pull valve cover gaskets and seals right into the crankcase .....


    ....... that sucks!! /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
     
  7. Beast388

    Beast388 1/2 ton status

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    The above info is right on the money!!

    A buddy of mine used to fun without a PCV valve on his 350. He couldn't figure out why he would get so much moisture in his oil. His oil would often times look like tapioca pudding. /forums/images/graemlins/rotfl.gif I told him to put a PCV in and it never happened again. Needless to say, they help keep the engine and its oil cleaner. /forums/images/graemlins/thumb.gif
     
  8. bigblock44k5

    bigblock44k5 1/2 ton status

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    PCV also helps with ring seal. Which is why you see race cars with vaccuum pumps on their motors.
     
  9. chulisohombre

    chulisohombre 1/2 ton status

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    yep like was said in previous posts.if the pvc is not hooked up the pressure will build up in the crankcase and seals will get messed up from the pressure.blowby gasses from combustion will also mix with the oil and become sludge from carbon buildup and the gases not escaping.my truck had just two breathers stuck into the top of the engine when i bought it and the oil got dirty within about 1000 miles and had to be changed.the gases were escaping but oil was also escaping from the pressure pushing out of the breathers.better to run with both hoses hooked up with pvc on one side going to the front of the carb and a breather hose going up to the air filter on the other side.if you look in any hains or chilton manual,you will find a diagram and expanation of why and how it is hooked up that way. /forums/images/graemlins/thumb.gif
     
  10. ntsqd

    ntsqd 1/2 ton status

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    [ QUOTE ]

    PCV systems are used on everything from regular cars / trucks to Winston Cup cars and Top Fuel Dragsters.

    [/ QUOTE ]

    No arguing that a PCV is a good idea on normally driven vehicles, but I've never seen one one a Top Fuel car and I've been around a few while crewing a Top Alcohol Dragster. I'd be surprised that a Cup car uses one as well. Those crankcase vapors can easily cause detonation with high compression ratios. Most Drag engines pull a vacuum on the crank case, but they do it with other means.
     
  11. diesel4me

    diesel4me 1 ton status Premium Member

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    The PCV valve is a calibrated vaccum "leak" that,if removed and plugged,will richen the fuel mixture on carburated vehicles,as well as all the other detrimental things already listed.
     
  12. bigblock44k5

    bigblock44k5 1/2 ton status

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    ntsqd, that is why i said they use vacuum pumps, which is the same idea of a pcv system.
     
  13. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    No arguing that a PCV is a good idea on normally driven vehicles, but I've never seen one one a Top Fuel car and I've been around a few while crewing a Top Alcohol Dragster. I'd be surprised that a Cup car uses one as well. Those crankcase vapors can easily cause detonation with high compression ratios. Most Drag engines pull a vacuum on the crank case, but they do it with other means.

    [/ QUOTE ]

    Exactly. You're missing the point. The point is that they pull a vacuum in the crankcase for a lot of reasons (ring seal, lack of leaks, etc).

    [​IMG]
    That's my buddy's race boat, the fastest drag boat in the world I believe the last two years.

    He runs an interesting looking system to pull a vacuum in the crankcase. You can see the two pipes, one on each side running towards the back of the boat.
     

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