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  1. #31
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by immortality View Post
    Fairly much. May as well just have 2 large breathers on the rocker covers and call it good.
    Thinking about it earlier: the pcv should be closed under WOT and If there is too much blow by for the one breather to handle then things like the dipstick could pop out. Putting another breather on to stop that reduces the effectiveness of the pcv system by making it harder for negative crankcase pressure. So it may be feasible to remove pcv and install a second breather while at the drag strip to purely allow for WOT pressure relief for the conditions of WOT racing. When your done for the day wack the pcv in to drive home and cruise the streets.

    Thoughts?


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  2. #32
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    If you can find some pics of 60s Nascar engines, they usually had two breathers per rocker cover. They were big engines, 7L, & pulling 6800-7200 rpm. No catch cans back then & they seem to work just fine.

  3. #33
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    HI
    Having a breather [s] only u will be absolutely guaranteed to have fumes and oil stain/residue over valve covers and possibly smell in cabin .
    The only crankcase catch cans that work most effectively by removing liquid are Ryco and Provent . A modified v8 probably needs 2x C/Cans of this type .

    Remember many car makers have half the valve cover devoted for oil separation . By comparison many v/covers only have a splash shield if that . The best idea is to separate oil in v/cover b4 it reaches so sump oil level does not drop . The Provent has provision to drain back to sump .Its a simple mod anyways to other makes .

  4. #34
    Do you ever leave? immortality's Avatar
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    Quote Originally Posted by BasicQ View Post
    Thinking about it earlier: the pcv should be closed under WOT and If there is too much blow by for the one breather to handle then things like the dipstick could pop out. Putting another breather on to stop that reduces the effectiveness of the pcv system by making it harder for negative crankcase pressure. So it may be feasible to remove pcv and install a second breather while at the drag strip to purely allow for WOT pressure relief for the conditions of WOT racing. When your done for the day wack the pcv in to drive home and cruise the streets.

    Thoughts?


    Sent from my iPad using Tapatalk

    A factory PCV system has a clean air side that feeds clean air into the crank case for the PCV system to then evacuate into the intake manifold. On the GM engines this is normally fitted on the throttle body. The issue you describe above is one of the failings of the PCV system, under certain engine conditions as you allude there is no flow via the PCV valve but there is excess crankcase pressure in which case the excess pressure flows back via the clean air side and makes a mess of the throttle body as witnessed by any high mileage GM/Holden throttle body.

    On later model MAF based cars you can't simply modify the PCV system with open breathers as the PCV system is effectively a controlled vacuum leak which takes air from the intake system that has been measured by the MAF. If you were to simply add open breathers you are creating a massive vacuum leak and letting unmeasured air into the system which will really stuff about with the tune.

  5. #35
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by swampy View Post
    HI
    Having a breather [s] only u will be absolutely guaranteed to have fumes and oil stain/residue over valve covers and possibly smell in cabin .
    The only crankcase catch cans that work most effectively by removing liquid are Ryco and Provent . A modified v8 probably needs 2x C/Cans of this type .

    Remember many car makers have half the valve cover devoted for oil separation . By comparison many v/covers only have a splash shield if that . The best idea is to separate oil in v/cover b4 it reaches so sump oil level does not drop . The Provent has provision to drain back to sump .Its a simple mod anyways to other makes .
    Fumes and residue, another ‘x’ in the breathers only column but maybe there are some guys that use that that can tell us to what degree.

    I have learnt that a well designed baffle under breathers and pcv is imperative for oil control.

  6. #36
    Sure why not? 76lxhatch's Avatar
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    Yes the breather side of a PCV system functions as intake at low rpm and (supplemental) pressure vent at high rpm, not just clean air. This needs to be improved for modified engines that breath more, no surprise as most other engine systems need upgrading to handle modifications.

    Unless there's something we can't see in the Torana photo (maybe there's a hidden PCV valve/line running to one of the cans?) I can't see how those breather lines are anywhere near big enough to cope with any rpm with atmospheric breathers, the engine would pressurise.

    If you simply can't use a PCV system because the valve won't work (vacuum issues) or its always overwhelmed (sustained high rpm, e.g. race car) then you start looking at (big) atmospheric breather systems. But if you can benefit from a vacuum system, why throw it away?

  7. #37
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by 76lxhatch View Post
    Unless there's something we can't see in the Torana photo (maybe there's a hidden PCV valve/line running to one of the cans?) I can't see how those breather lines are anywhere near big enough to cope with any rpm with atmospheric breathers, the engine would pressurise.

    If you simply can't use a PCV system because the valve won't work (vacuum issues) or its always overwhelmed (sustained high rpm, e.g. race car) then you start looking at (big) atmospheric breather systems. But if you can benefit from a vacuum system, why throw it away?
    Maybe the owner didn’t want to let trivial things like excessive crankcase pressure get in the way of a neat install? Or is it a case of not fully understanding what that system needs to work?

    So 37 post in there hasn’t been any information put forward informing me there is more to those remote catch can minus pcv systems than I see at face value, not for a street strip type car anyway. I have been reminded they are illegal on the street, some have said they can be fumey and smelly, sized correctly they can have an advantage over pcv system at WOT but sacrifice too much when not at WOT and my suspicions of them being installed as form over function when used on the street has been reinforced. There is also excellent first hand information from LXCHEV indicating difference in power between functioning pcv v no pcv isn’t worth discussing. The M E Wagner adjustable pcv valve is worth investigating more too for its benefits.

    Thanks for all the replies guys. I think I will stick with the set up similar to pic 2 in post 1.

  8. #38
    Do you ever leave? EH179's Avatar
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    The way i see it is, there are no more ponies to be found running catch cans, it is considered illegal on the street and..... they stink when they vent.

    I run a ~500hp engine on the street with a factory PCV system and have no problems. A very minute amount of oil gets in the intake, but it doesn't appear to affect operation.

    That's all i have on the subject.

  9. #39
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by EH179 View Post
    The way i see it is, there are no more ponies to be found running catch cans, it is considered illegal on the street and..... they stink when they vent.

    I run a ~500hp engine on the street with a factory PCV system and have no problems. A very minute amount of oil gets in the intake, but it doesn't appear to affect operation.

    That's all i have on the subject.
    I think if you were the defense lawyer for the pcv valve v remote catch cans you have summed up nicely.

    Case closed.


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