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Something Is Screwed Up - Car Revs To 1500 For No Apparent Reason

Discussion in 'Technical Q&A' started by donaldh2o, Dec 2, 2003.

  1. donaldh2o

    donaldh2o Karting

    Nov 10, 2003
    143
    Irvine CA
    Full Name:
    Don
    Trying to set the gap, timing and carbs on my '76 308 all at the same time and the harder I work the behinder I fall.

    Originally a U.S. car, years ago I had the euro cams, fly wheel, single points and exhaust installed.

    I set the single points to .012 but the dwell is measuring only 10'. It should be 34'. Will bench set that before I continue.

    Timing is set to 1/2" above 7', my approximation of 10' after TDC.

    To set the carbs, I'm using the U.S. shop manual: Fully tighten screws "C" then unscrew them for 3 turns. With engine running, reach 900 - 950 rpm by operating on the two screws "A". Using the synchrometer, adjust first the two(?) carbs on the left head (front)(?) then adjust those of the right head (rear)(?) by operating screws "B". Using the synchrometer, balance the two carb lines. Diddle screws "D" to account for variations between joined carburetors. Bring the idle back to 900-950 by screwing or unscrewing screws "A".

    Problem is I can't get the car to idle at 950 rpm. Adjusting the carbs, I get it to run smooth at about 650-700 rpm, but then it begins on its on to creep up to 1200 rpm, then back to low idle. Does the same thing when driving the car. Slow to return to idle, even staying at 2000 rpm at traffic lights. I bring it home and it continues to idle at 2000 rpm for several minutes before finally returning to the low idle.

    I'm using an STE SK 1-30 kg/h synchrometer. The instruction sheet says Weber carbs should be adjusted to 1.8 to 2.5 kg/h. To get my car to run even as low as 700 rpm, the synchrometer is reading 7 kg/h on all 8 carb throats. At 1.8-2.5 kg/h, I don't think the car will run at all.

    Plugs are RapidFire #5 and have less than 10,000 miles on them.

    Also, the fast idle device is adjusted completely back for now, so it is out of the equation.

    Possible problems:

    1. The erroneous dwell setting somehow affects the idle.

    2. The points advance is not returning to normal, thus causing the car to idle fast and erratically. I don't know how the advance works on the single point setup. Weights??

    3. The carburetor settings are different for the single point setup and the U.S. manual is the wrong manual to use or I'm confused about what left head and right head mean?

    4. The carbs (one or more) need repaired or cleaned. To my knowledge, they've never been rebuilt.

    5. There are no instructions for setting the fuel/air mixture screws C.

    6. All of the above.

    7. I have no idea of what I'm doing and should take it to a Ferrari shop.
     
  2. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    You won't be able to get 2 kg/hr with the idle at 1000rpm. I set mine to 3.5-4.0 kg/hr with idle at 1000rpm.
     

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