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valve cover breather upgrade?

Discussion in 'General Tech and Maintenance' started by dc4dude, Jan 28, 2009.

  1. dc4dude

    dc4dude Member

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    :confused::confused:is it true that if you add a pump that will pull vacuum through an engine's valve cover, and essentially from under the piston, can add horse power? my friend is an old hot rodder, he has a 528 bb chevy that has an angle cut 3/8 inch pipe that goes from his headers (collector) to his valve covers. he was saying something about the piston rings being more efficient whe the oil side is under vacuum. anyone know about any truths to this? will it work on a 4 cylinder engine?
     
  2. INJEN78

    INJEN78 HS LEGEND

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    it actually does make more power with a vented valve cover,i dont know if it needs a "pump" but i know that if you relieve pressure it works,
     
  3. TurboMirage

    TurboMirage YEEAAAHHH VIP

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    im not too sure about what your buddy did but it kinda seems wrong to flow exhaust gases through your top end.

    the breather is there to pull blowby and crankcase gases into the combusion cycle. if you are really worried, run a catch can.
     
  4. INJEN78

    INJEN78 HS LEGEND

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    no you ave to actually hookup a valve type deal to the exhaust
     
  5. TurboMirage

    TurboMirage YEEAAAHHH VIP

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    still sounds rediculous. id love to see some actual facts.
     
  6. INJEN78

    INJEN78 HS LEGEND

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    its true,som dude made an extra 10hp just from venting his VC,on a turbo build
     
  7. K2e2vin

    K2e2vin Senior Member

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    The exhaust slash-cut method works off of the same principle as carburetors; Bernoulli's principle. There's a check valve to prevent gas reversion during lower exhaust velocities.

    Also, no, venting the valve cover does not mean more horsepower. How it's setup stock, is vacuum. Venting it introduces ambient air pressure which means the motor has to work to pump air in and out. Venting is only beneficial in boosted setups(where blow-by pressures are higher than a NA engine); and even then the slash-cut and vacuum pump method is the more popular methods among FI racers.
     
  8. TurboMirage

    TurboMirage YEEAAAHHH VIP

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    now THAT makes sense to me.
     
  9. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Vacuum on crankcase side = good
    Vacuum on valvetrain side = good

    If you're getting exhaust flow from the valve COVER into the combustion chamber, you've got some SERIOUS problems.

    I say everyone should dry sump their engines. Yum.
     
  10. efhondakid

    efhondakid My name is Byron. VIP

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    1 person likes this.
  11. 97hatch

    97hatch ?

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    Vacuum on the crankcase is very good but to much of a good thing is bad. If you pull to much vacuum on your engine with a vacuum pump it will actually suck the oil out of the bearings and well its gona blow/spin a bearing


    As for the dry sump its the only way to go on a race car i belive that it is the only way to go. Thats why i have bought a 3 stage pump for my turbo build. Its pretty hard to find a drysump pump for a reverse rotation engine. I had to have mine custom built.
     
  12. TurboMirage

    TurboMirage YEEAAAHHH VIP

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    just what i was looking for EF. thanks.
     
  13. YBLEGAL

    YBLEGAL Regular Member w/ Cheese

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    Vac on both sides at the same time = not good/not possible.

    Put vac on the crankcase vent through a catch can with the pump and put a breather on the valve cover; I believe is the best setup from my reading.... comments?
     
  14. efhondakid

    efhondakid My name is Byron. VIP

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    The vaccum pump or the pr0n? You going to do a vac pump setup? Id like to see if there are any noticable gains on the dyno with one.
     
  15. TurboMirage

    TurboMirage YEEAAAHHH VIP

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    the vac pump idea which i was originally calling BS on.
     
  16. K2e2vin

    K2e2vin Senior Member

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    Very possible and very good. Pressure is introduced via blow-by and various cracks and crevices. The crankcase and head would experience about the same vacuum/pressure...they have oil galleys for draining oil from the head.

    All that would do is circulate "fresh air" through the motor; only solves the issue of getting blow-by gasses out of there. The OE system is set up like this(for emission reasons). Ambient pressure means more work on the internals via windage and pumping losses. Also, circulating system means there's slight vacuum in the crankcase already(refer to Bernoulli's principle of gas velocity in relation to internal pressure).

    Most people have issues with trying to get high vacuum in the crankcase, especially Honda engines. I don't think you would have problems with vacuum sucking oil from the bearings(this would mean the effective oil pressure would also drop).
     
    Last edited: Jan 30, 2009
  17. 97hatch

    97hatch ?

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    actually you can with a good vacuum pump it is verry posible to pull 15inches or more of vacuum and that is to much
     
  18. K2e2vin

    K2e2vin Senior Member

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    Thing about the larger pumps is they're designed to spin the opposite direction(designed for CW rotation engines). In addition to that; you'd only be able to pull high vacuum if you can completely seal the motor. A couple of builders have tried(completely sealing) but with no success. You'll probably end up losing power to drive a higher vacuum pump too(once you get enough vacuum, any more would not net anymore gains in power)..
     
  19. efhondakid

    efhondakid My name is Byron. VIP

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    Belt driven pumps I would imagine would rob more than then they would help on a four banger but the GM smog pumps, its not parasitic so why not run it? If it helps, sweet, if not nothing lost right?
     
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