308 carb sync ... motor slow to return to idle | FerrariChat

308 carb sync ... motor slow to return to idle

Discussion in 'Technical Q&A' started by F308 MAN, Jun 7, 2008.

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  1. F308 MAN

    F308 MAN F1 Rookie

    Jan 19, 2004
    2,907
    Isle of Man
    Full Name:
    Dave S
    #1 F308 MAN, Jun 7, 2008
    .... i am synchronising the carbs.
    all four carbs (and barrels) are nicely in sync.
    .... but when i rev the motor, the revs are more often than not, slow to die down.

    no vacuum leaks, cable is slack, stops are just in contact with throttle stop levers, and everything else seems spot on.

    any ideas ?
    many thanks in anticipation.
    david
     
  2. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    12,661
    San Carlos, CA
    Full Name:
    Mitchell Le
    #2 yelcab, Jun 7, 2008
    Carbs will do that. How slow is slow, for you?
     
  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,123
    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    #3 Steve Magnusson, Jun 7, 2008
    Please quantify the inlet airflow measurement -- how many Kg/hr entering each barrel at idle?
     
  4. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,223
    TN
    #4 308GTS, Jun 7, 2008
    I think Steve it on the right track. Your kg/hr are most likely too high. I would richen the mixture, the idle will go up but just bring it back down to 1K eventually you will get it correct.
     
  5. thecarreaper

    thecarreaper F1 World Champ
    Silver Subscribed

    Sep 30, 2003
    17,576
    Savannah
    #5 thecarreaper, Jun 7, 2008
    i found 3 1/2 to be a baseline for my carb cars, +1/2 on the carb barrel with the vacuum line for the brake booster.
     
  6. F308 MAN

    F308 MAN F1 Rookie

    Jan 19, 2004
    2,907
    Isle of Man
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    Dave S
    #6 F308 MAN, Jun 8, 2008
    not quite certain steve, as i am getting on in years, and not too good on the old memory thing, i adjust the choke on the flowmeter to give me an easy to remember datum .... having said that, with the choke closed i think around 3.5 - 4.

    late last night, i tootled with the linkages .... i think that maybe the lower turnbuckle adjuster is at it's limit and won't shut off the rear bank.

    it's now 6:30 am, sunday morning .... and after another almost sleepless night, i return to the garage for hopefully, a more succesful day.

    many thanks for your help .... please keep your comments coming in.

    cheers,
    david
     
  7. F308 MAN

    F308 MAN F1 Rookie

    Jan 19, 2004
    2,907
    Isle of Man
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    Dave S
    #7 F308 MAN, Jun 8, 2008
    S O R T E D ! ! ! !

    many thanks, chaps .... one or two idle mixture screws a little too far out for my liking, but all is spot on, now.

    it was in fact the adjustment of the idle mixture settings.

    time for a beer !

    thanks again, d
     

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