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Thread: Crankcase Ventilation On 3.5 Why No Pcv Valve ???

  1. 2nd February 2007, 09:08 AM #1
    lokka Guest

    Crankcase Ventilation On 3.5 Why No Pcv Valve ???

    Gday guys

    Im haven dramas sorting the crankcase ventilation on a 3.5 the good book says a filter fed clean air via air cleaner is hooked up to a vent on the top of the block bhind valley cover then two tubes and flame traps from the rocker covers into the vacume of the carbys ...

    Thats all good as my set up is diferent on the p motor with a holly and the one in question is a 3.5 with holly ..

    My p motor runs a pcv valve in the rocker cover like the norm and feeds in under the holly ..

    The motor in question is a 3.5 with holly and the crank vent sistem was crap and filled the air cleaner with oil cause the 2 vents coming out the rocker cover were fed into it ..

    Now the prob is if i hook the 2 vent pipes into te bottom of the holly like mine it draws air in through the top of the oil cap which has the provision for a small filter ..

    Should i just fit a filter to the cap and run sum sort of pcv valve or just the filter on the cap and no pcv valve ...

    As for the std set up the flame traps on the vent tubes in the rocker covers do bugger all in the way the air goes through em or wil they stop any oil going through the hose as it must have somthing in line to stop the oil from going through the hose ...

    Cheers guys

    Chris
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  2. 2nd February 2007, 09:17 AM #2
    rangieman's Avatar
    rangieman
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    My old rangie had a vitesse 3.9 and a horrible holly it had the hoses from both rocker covers to a y piece and then a pcv valve to the crap carby worked fine except for that holly

    the pcv valve was just behind the carby
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  3. 2nd February 2007, 06:38 PM #3
    Bush65
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    The flame arrestors do not stop oil. They are there in case the engine back fires through the carby.

    When I put a 4.6 short motor with 3.5 heads etc. in my rangie, the new block did not have the breather at the back of the valley, only the hoses from the rocker covers.

    I had a problem with oil loss into the carb for a long while. Had to run the breather hoses into a dropout box before the carb.
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  4. 2nd February 2007, 07:22 PM #4
    PhilipA
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    To answer the question, The crankcase vents vent into the sides of the Strombergs before the throttles, so no PCV valve is needed as there is no additional air coming in after the throttle plate. There is vacuum because they feed in after the vacuum piston.
    If you use a carby without the facility to feed air in before the throttle, you need a PCV valve.
    Rover V8s have oil separators inside the rocker covers.There is a sleeve that allows air in at the back, then travels to the front before exiting into the vents.
    regards Philip A
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  5. 2nd February 2007, 08:48 PM #5
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    rangieman
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    Quote Originally Posted by PhilipA View Post
    To answer the question, The crankcase vents vent into the sides of the Strombergs before the throttles, so no PCV valve is needed as there is no additional air coming in after the throttle plate. There is vacuum because they feed in after the vacuum piston.
    If you use a carby without the facility to feed air in before the throttle, you need a PCV valve.
    Rover V8s have oil separators inside the rocker covers.There is a sleeve that allows air in at the back, then travels to the front before exiting into the vents.
    regards Philip A
    and he has a holly so a pcv valve is needed
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  6. 2nd February 2007, 09:43 PM #6
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    Quiggers
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    You need to read my thread : OIL LEAK GOES BAD, etc ----

    the PCV firetrap canister was full of oily crap as were the lines (tubes) to the inlet manifold -

    YUK!

    just read the story, lokka.. and report on your fndings.....
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  7. 3rd February 2007, 07:13 AM #7
    lokka Guest
    Ok guys ive sorted the problem by running the two breathers from the rocker covers to a t peice behind the carby then a in line pcv valve and then into the inlet under the carby and a sexy blue filter ontop of the oil filler ...

    Now my only worry is the little trail of smoke coming out the oil filler at idle or when reving only stops on back down id say the engin is getin tired as it has a few bottom end noises ...

    Cheers for the advice guys

    Chris
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