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Thread: Apache with dual carbs

  1. #1
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    Apache with dual carbs

    I have a '58 Chevy Apache stepside 235 ci which has had an uprated engine and has been fitted with an Offenhauser manifold and twin Rochester Bs. This seems to have caused two problems. The first is that the linkage doesn't return properly when idling so it runs too fast but if a stronger accelerator spring is fitted the pedal won't go down. With one carb the linkage was directly below the carb and so would pull the lever down but now it has to pull both down from a centre point, so it's a clumsy operation. The second is that it runs too rich and the plugs are always black. I've tried carb kits, smaller jets (48s) and now new carbs but nothing seems to work. I've read many times that it should only have one carb and two never run properly. When I adjust the mixture screws they're ready to fall out, and I never need to use the choke. The dual set-up is so popular that I can't believe it's impossible to overcome these problems. Any ideas?

  2. #2
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    Pics would probably help determine what's going on. It sounds like a design issue with the return spring.

    Aren't mixture screws at their richest when screwed out?? A cheapo vacuum gauge could be in your future.

    Chris

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  3. #3
    NSRA member kapri's Avatar
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    Just because everyone has them fitted doesn't mean they run right Mixture screw is wek =in , rich = out so more you wind it out richer it gets.

    A shop I know fitted 2 Stromberg 97 on a 4 banger , it would only idle and wouldn't pull away ...WAY too big a hole in both to make it work, like putting twin 45s on a standard Anglia engine.

    Try talking to someone who has it fitted and is happy with the set up, no point reinventing the wheel.

    In the past I've found the 235 works VERY well with a single choke Weber ICH ( with 29mm venturi ) as fitted aftermarket to Series Land Rovers.

    Always worth trying what I did initially with the Strombergs . Make up a blanking plate to fit undermeath one carb and see how it goes. Then swap it to other carb for a try. That way you'll know if it's purely the fact it's twins playing up , or both individually, aren't set up correctly.
    Galations 6:7

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    Moderator Brizey's Avatar
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    The not returning to idle problem could be the carbs are not synchronised and 1 is open more than the other...
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  5. #5
    NSRA member mygasser's Avatar
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    Quote Originally Posted by Brizey View Post
    The not returning to idle problem could be the carbs are not synchronised and 1 is open more than the other...
    i wondered that.

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    Well well... you learn something every day. I always thought that by turning the mixture screw anti-clockwise it was allowing more air into the carb. I've adjusted them and I'll clean up the plugs and see if they're less sooty now. I'll try adjusting the linkage again and see if I can get it return to its lowest point. The Throttle switch on the dash isn't connected - don't know if that makes any difference. I'd like to experiment with the blanking base plate idea, but that'll take some time so I'll get back to you, but thanks for your help so far.

  7. #7
    NSRA member mygasser's Avatar
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    if you try the blanking plate under the carb deal make sure the butterfly of that carb can still move full travel without binding against the plate. if it binds it'll hold the other still functioning crab wide open, not good.
    neil.

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