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Thread: new engine & Weber tuning help needed:

  1. 07-15-2019, 02:40 PM #1
    Chris Steineger
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    new engine & Weber tuning help needed:

    We've just built & installed in a '66 911, a 2.5 liter short stroke motor. 9.5:1 compression, E/S grind cams, Weber 40 IDAs

    Webers have 34mm venturis; 150 main jets; 50 idle jets; F3 emulsions

    Engine has 20 minutes of time on it, but still pops and minor back fires. It bogs badly when advancing the throttle.

    Not sure if its carb, timing, vacum leak ?

    What are your thoughts ?
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  2. 07-15-2019, 02:54 PM #2
    edmayo
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    There's a million things it could be!! If you're not sure whether it's timing I suggest you check it, but for sure I'd start with 55 or maybe even 57 idle jets. You should not need more than a 57. Just from curiosity,,,what is an E/S grind cam? This is where you get to start diagnosing. There are usually no easy answers, only simple ones when you finally find them.
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  3. 07-15-2019, 06:41 PM #3
    Richy
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    Are the accelerator pump squirt nozzles working ?
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  4. 07-15-2019, 07:04 PM #4
    eaton
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    I found Paul Abbott's set-up and tech info incredibly helpful when going through this. Here's a good place to start: http://www.performanceoriented.com/special-procedures-1
    '66 912 with a 2.2
    '62 Lotus Seven S2
    '66 Lotus Elan
    '63 Karmann Ghia convertible
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