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  • SU carbs

    Hey everyone

    I got the marlin running again for the first time since before xmas and all is looking, possibly even be at stoneleigh with it.

    One problem i have was the car idles at a high rpm and i cannot slow it down anymore, even with the throttle cable taken off it still revs high, i decided to mess about and with a bit of cloth over the air inlets as it does not have any filters fitted, this made it run alot slower but still the revs would quickly pick up and never sounded as though it was starved of air when i opened the throttle.

    So would i be right in thinking i need to give the carbs something to slow the air down as it is twin 1 3/4SUs on a triumph 2.5. I was talking to a friend who knows a bit about the SUs as he messes about with Rover V8s and he says K and N filters will not restrict the air flow enough and i will get high fuel consumption but not alot of power, so was wondering what people have used that fit in the space for air filters, or am i barking up the wrong tree??

    Cheers in advance

  • #2
    Re: SU carbs

    You should be able to adjust the idle speed using the throttle stop screws on the carbs. These set the amount that the butterfly valve is opened when there is no throttle depression. If you can't adjust the idle speed adequately using these there is something amiss with the carbs.

    Robin

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    • #3
      Re: SU carbs

      Hi Tom, Is it possible the carbs are not in sink! The throttle linkage may not be linked properly, one carb maybe idling higher than the other. Try slacking the linkage between the carbs off and see what happens. Also you may have an air leak between carbs and manifold giving you a weak mixture.

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      • #4
        Re: SU carbs

        Cheers for the response i will give them both a try today. With regards to the carbs being in sink my left hand one does seem to be pulling more air than the right. But all the revs pick up quickly and it sounds as though it is running well and they are not to far out?

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