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Thread: How To: Set CO Dwell

  1. #1
    Admins Never Retire Ron's Avatar
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    How To: Set CO Dwell

    Corrected:
    How2COCorrected.jpg
    If The Anti-Tamper Plug Is In Place, See:
    How To: Remove CO Anti-Tamper Plug Here
    Attached Images

  2. #2
    Not really banned Michael's Avatar
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    What is the breather hose? Is that the big hose on the other side where the oil fill chamber is or is there a smaller one? The pic is pointing to something but I can't make it out.

  3. #3
    Senior Member Bitsyncmaster's Avatar
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    Your text in the photo should say "=20 deg. on eight cylinder scale".

    If you mean the large hose that goes to the air cleaner, That hose is just open in the air cleaner so blocking it does not simulate if the air cleaner was on.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #4
    Admins Never Retire Ron's Avatar
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    Quote Originally Posted by Michael View Post
    What is the breather hose? Is that the big hose on the other side where the oil fill chamber is or is there a smaller one? The pic is pointing to something but I can't make it out.
    The "Oil Fill Tube/Hose":
    OilFillTube-Hose.jpg

  5. #5
    Admins Never Retire Ron's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    Your text in the photo should say "=20 deg. on eight cylinder scale".
    Yep! Will fix shortly...

    THANKS!

    Quote Originally Posted by Bitsyncmaster View Post
    If you mean the large hose that goes to the air cleaner, That hose is just open in the air cleaner so blocking it does not simulate if the air cleaner was on.
    No. To be clear:

    The Large Breather Hose goes to the atmosphere (eventually). The Small Breather Hose goes to the Oil Fill Cap.
    The Oil Fill Cap has two hoses going to it. Both supply vacuum! [This puts the crankcase under vacuum.] Removing the breather creates a vacuum leak, because instead of having vacuum from the air fuel unit, the breather and thus the Small Breather Hose, would be open to the atmosphere...
    So, you have to plug the Oil Fill Cap Tube/Small Breather Hose connected to it (depending on where you separate it).

    You can see this if you remove the hose from the cap and place your finger over the tube then seal the bottom of the cap with your palm.
    ( It is quite strong ;-)

    Technically, the CO should be set with everything in place as it will be ran during normal operation, but it can be hard to get to with the breather in place.
    This is why it should be double checked and readjusted if necessary, while in place.
    Last edited by Ron; 12-13-2015 at 02:53 PM.

  6. #6
    Not really banned Michael's Avatar
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    Thanks, with my cams the mixture is hard to dial in, but I have never set it with the hose blocked off. However on my car the vent hose has it's own filter since I use the stainless cleaner. Should I remove that line and plug it at he cap?

    mixture1.jpg

  7. #7
    Admins Never Retire Ron's Avatar
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    I can't make out how it is plumed in the pic...

    As I mentioned, the best way is to set the CO with everything in place as it will be ran during normal operation (if you can get to it ;-)

    One thing- It seems you have the the Oil Fill Cap connect to the "extra" filter instead of the Small Breather Hose. If that is the case, note that the crankcase is normally under vacuum (closed system). This would make it an open system (like a lot of early model vehicles/defeated PCV system), which ALL of the settings etc do not expect and prone to throw things off..., no longer clearing/burning blow by gases as intended (Gains v/s keeping it clean is debated endlessly ;-).

    But non-stock cams change things too...
    So FWIW- Personally, I'd add a tube to the breather and use a CO analyzer to set it.

    (There is something bugging me about that cap I want to check out, but not get into and confuse things now...I'll post up if it turns out to be anything)
    Last edited by Ron; 12-13-2015 at 03:50 PM.

  8. #8
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by Michael View Post
    Thanks, with my cams the mixture is hard to dial in, but I have never set it with the hose blocked off. However on my car the vent hose has it's own filter since I use the stainless cleaner. Should I remove that line and plug it at he cap?

    mixture1.jpg
    NO. That must be open. If the car is operating correctly there is no reason to disconnect anything. If the car isn't operating correctly, fix that first.
    Dave S
    DMC Midwest - retired but helping
    dswingle@DeLorean.com

  9. #9
    Admins Never Retire Ron's Avatar
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    I corrected information in the pic (Post #1) that was causing some confusion.

    NOTE- If your D's plumbing is not stock (closed system), this How To Does Not Apply.

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