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Thread: Car running rich after installation of PCV??

  1. #1
    Guest Paul Y's Avatar
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    Car running rich after installation of PCV??

    Why do I always do those easy jobs 30 minutes before I need to be somewhere....

    Going through my list of things to do and got to 'Instal PCV'.

    Easy, Unbolt carb, put in 1" spacer with PCV take off, connect hoses reinstall carb.

    Start car.

    Car surges really badly but put this down to being cold.

    Allow to warm up and adjust idle speed.

    Car smells like it is really running very very rich, so much so it makes my eyes water.

    Not taken it for test drive as there is obvioulsy something wrong.

    Would the 1" spacer make that much of a differance to the way the engine runs?

    Have I made a school boy error?

    Carb is a 830DP Holley on an Edelbrock RPM manifold.

    Oh Yea, car was running really well before I did this 30 minute job....

    P.

  2. #2
    NSRA member Klunk's Avatar
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    On my old Rover I put a restrictor in the hose up to the PCV take off. It was a piece of aluminium (an old Kenlowe support cut down) I drilled a 2mm hole in it. This got my revs back down from 2 1/2 grand to about 800 rpm.

    Not sure if this is the best solution, but it worked for me. Otherwise my carb was just sucking in loads of 'fresh air' from the rocker covers.
    Don't adjust your sets. Yes I have just been on the forum!

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  3. #3
    Guest Paul Y's Avatar
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    I suppose the first thing to do would be to disconnect the PCV and see if it still surges and runs rich. At least then I can elimante that.

    Could it be that I just need to adjust the idle curcuits?

    Not 100% comfortable with Holley carbs so any other pointers would be grateful.

    P.

  4. #4
    Moderator jsf55's Avatar
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    Pretty sure thats whats required, i used and old car valve bolted into the rocker cover, a tip from maurice T, and it reduces it just enough

  5. #5
    NSRA member Klunk's Avatar
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    Disconnect the PCV and blank the spacer take off, then see if it all returns to how it was before you changed it. If it returns to normal, reconnect and use a restrictor.

    TBH when I first connected mine I squashed the rubber hose from the PCV til it ran nicely then worked out approx what sort of size hole it would need to match it.
    Don't adjust your sets. Yes I have just been on the forum!

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  6. #6
    Guest Paul Y's Avatar
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    OK. am I being thick here....

    You are suggesting that I in effect put a restriction on the hose leading to the PCV to stop the engine dragging in to much air?

    But would that not make the car run weak rather than rich if it is sucking in too much air.

    I do not have a high idle, in fact just the reverse.

    P.

  7. #7
    NSRA member Klunk's Avatar
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    Quote Originally Posted by Paul Y View Post

    You are suggesting that I in effect put a restriction on the hose leading to the PCV to stop the engine dragging in to much air?
    Yes, that is what I am suggesting. Due to the car getting more air 'underneath' it will draw more fuel from the carb to compensate....don't ask me how....it just does. This in turn makes it idle quicker/ rougher. It's the equivalent of a leaky inlet manifold.

    Try what I said and I am pretty darned sure that'll sort it.
    Don't adjust your sets. Yes I have just been on the forum!

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  8. #8
    NSRA member Klunk's Avatar
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    Quote Originally Posted by Paul Y View Post

    I do not have a high idle, in fact just the reverse.

    P.
    So you are saying with the PCV attached the idle drops and the car runs rich.
    Don't adjust your sets. Yes I have just been on the forum!

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  9. #9
    Moderator jsf55's Avatar
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    The first answer should have been do you need it? does the engine run any other sort of breather system or vents?

  10. #10
    NSRA member Klunk's Avatar
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    If that's the case, then yours seems to be acting different to mine, mine rose!
    Don't adjust your sets. Yes I have just been on the forum!

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  11. #11
    NSRA member Captain Scarlet's Avatar
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    Quote Originally Posted by Paul Y View Post
    OK. am I being thick here....

    You are suggesting that I in effect put a restriction on the hose leading to the PCV to stop the engine dragging in to much air?

    But would that not make the car run weak rather than rich if it is sucking in too much air.

    I do not have a high idle, in fact just the reverse.

    P.
    Well thats just what i was thinking Paul, it is normally the case that the mixture needs more fuel when adding positive crankcase breathing ,its sometimes difficult to help when not there with the vehicle ,but while the carb was off is it possible the floats opperation was comprimised,maybe shut off valve not seating or the float has stuck up and the carb is flooding,have you checked the sight plugs in the side of the float chambers.

  12. #12
    Guest Paul Y's Avatar
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    Running a breather in each rocker cover.

    Car does 'breath' quite heavily when you get on it an leaves the covers with a nice oil bath.

    It has been suggested by the engine builder to install the PCV system, only just got around to fitting it.

  13. #13
    Guest Paul Y's Avatar
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    Quote Originally Posted by Captain Scarlet View Post
    Well thats just what i was thinking Paul, it is normally the case that the mixture needs more fuel when adding positive crankcase breathing ,its sometimes difficult to help when not there with the vehicle ,but while the carb was off is it possible the floats opperation was comprimised,maybe shut off valve not seating or the float has stuck up and the carb is flooding,have you checked the sight plugs in the side of the float chambers.
    Possible, I will have look tomorrow.

    Would be surprised though as I just took the carb off, put it on the bench and then refiited it.

    Mind you nothing really surprises me anymore....

    P.

  14. #14
    NSRA member Captain Scarlet's Avatar
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    I assume you have used an OE type PCV valve in the valve cover,

  15. #15
    Moderator jsf55's Avatar
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    When u fitted the spacer to the manifold, where did u connect the pcv valve too ?

  16. #16
    Admin IanT's Avatar
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    Surely the PCV valve is it's own restrictor, that's what it's designed to do..

    Is the spacer plate (or gasket) interfering with movement of throttle butterflies?
    IanT (°||°)
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  17. #17
    Guest Paul Y's Avatar
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    Quote Originally Posted by Captain Scarlet View Post
    I assume you have used an OE type PCV valve in the valve cover,
    I have used a PCV from a 455 Pontiac, takes off from the rocker cover.

    Quote Originally Posted by jsf55 View Post
    When u fitted the spacer to the manifold, where did u connect the pcv valve too ?
    PCV connected to the PCV fiiting on spacer. Only reason I fiited a spacer was to get a PCV connection.

    P.

  18. #18
    Guest Paul Y's Avatar
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    Had a suggestion from another forum that it could be the power valve opening to early as the engine should now be seeing more vacuum?

    Thoughts?

    P.

  19. #19
    NSRA member langysrodshop's Avatar
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    Paul for the PCV system to work correctly you don't have a breather in each rocker cover, Air is drawn from the airfilter and is drawn through the engine crankcase and then out through the PCV valve to the large vacuum fitting on the base of the carb.

    Why did you have to use a spacer ???


    Quote Originally Posted by Paul Y View Post
    Running a breather in each rocker cover.

    Car does 'breath' quite heavily when you get on it an leaves the covers with a nice oil bath.

    It has been suggested by the engine builder to install the PCV system, only just got around to fitting it.
    Any advice or help given is actually based on having done the job, not read about doing it or Googling it.

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  20. #20
    NSRA member Dusty's Avatar
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    Quote Originally Posted by langy View Post
    Paul for the PCV system to work correctly you don't have a breather in each rocker cover, Air is drawn from the airfilter and is drawn through the engine crankcase and then out through the PCV valve to the large vacuum fitting on the base of the carb.

    Why did you have to use a spacer ???
    I have a Moon breather in one rocker cover. The other rocker cover has the PCV in connected to the carb, as Langy says. If you have a breather in the cover with the PCV in, you are probably drawing air in through it, leaning out the mixture.

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