Volvo RWD 120-130 Forum

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Timing & Carbs--- Rookie Questions 120-130

posted by  Dolores67 on  Wed Mar 26 13:14 CST 2008
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last visit: Tue Feb 5 17:48 CST 2013
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Having never attempted a distributor conversion or an SU tuning after having the carbs rebuilt, I drank some John Courage and took the plunge. I installed an electronic ignition from http://www.hot-spark.com/ with the kit from IPD to avoid cutting into the shielded cable,and had Tom Bryant redo the carbs. The engine runs beautifully, but I can't seem to nail down the fine tuning of the timing and carb adjustment, nor do I really understand the link between the two.

When I advanced the timing to 20 degrees as a starting point and balanced the carbs, the engine idled at 1200 RPM, which seems a little high to me. If I advance the timing to 30 degrees and lower the idle RPM to 1000, the engine diesels when I shut it off. Once I set the timing and the engine is running smoothly do I leave the timing alone and just adjust the carbs or work between them? Lastly, what does the term "total advance" refer to?

Thanks, I hope I am being somewhat clear in explaining something I am not familiar with.

B








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    Timing & Carbs--- Rookie Questions 120-130

    uid 5322's pic
    posted by  alschnertz on  Wed Mar 26 15:00 CST 2008
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    last visit: Fri Oct 24 10:32 CST 2014
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    I'd start off with the timing set around 20 degrees at 1500 rpm and leave it there, then adjust the carbs until you can get the idle down.
    Make sure you have no intake gasket leaks or other sources of vacuum that are unplugged.
    Also make sure your fast idle screws are not preventing the carbs from returning to idle.
    Are you sure the throttle plates were closing all the way?
    Do you have secondary butterflies that may be leaking?
    With that dist. set-up and rebuilt carbs, you will be able to get the idle down.
    If not, take a ride down to Southbury and we'll put our heads together and figure out what's wrong.

    --
    Tom - '60 544, '68 220S, '70 145S, '86 745T, '06 Mazda MPV








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      Timing & Carbs--- Rookie Questions 120-130

      posted by  Dolores67 on  Wed Mar 26 16:36 CST 2008
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      last visit: Tue Feb 5 17:48 CST 2013
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      Thanks for the offer to help. I don't think I have any leaks etc., just a lack of experience. What is the idle speed I should be aiming for? I read one post that indicated 600 RPM, not sure she'll run at that speed. More fiddling tomorrow.








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    Timing & Carbs--- Rookie Questions 120-130

    posted by  122_Canadian on  Wed Mar 26 13:28 CST 2008
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    last visit: Tue Oct 20 07:51 CST 2009
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    SU's can be tricky - but are perfectly logical if you have the time to figure them out...if not have a look at the follwing posts by University Motors on You Tube. Someone posted the link here, this guy's my new hero.

    http://www.youtube.com/user/Universitymotorsltd

    Total advance refers to how much advanced the spark will be when the distributor stops advancing...therefore total. The start point is usually around 10 degrees BTDC IIRC.

    Craig







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