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Thread: Dcoe to idf

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    Spanner Monkey

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    Dcoe to idf

    Hi currently running twin 40dcoe on my xflow the choke sizes are 34 im going to twin 44 idf what chokes would i need and would i use same size jets? Ahy help thanks

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    Re: Dcoe to idf

    Hello
    That is a very broad question.....you would need to specify the engine build for a start. And what is the application.....street, strip??

    But why IDF? for the ram effect? If the head is not properly ported the gains may be negligible.

    You appear to be running reasonably large chokes already; and 44IDF may be overkill for what I presume to be a 1.6 street engine.

    Jetting would always depend on air flow, bigger carbs with bigger chokes need more fuel; and would decrease intake velocity low down; affecting driveability.

    You may want to consider further tweaking the 40s.....eg better flowing air horns, experimenting with emulsion tubes......etc.
    Regards,
    Kevin

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    Re: Dcoe to idf

    Quote Originally Posted by djaminhi View Post
    Hello That is a very broad question.....you would need to specify the engine build for a start. And what is the application.....street, strip?? But why IDF? for the ram effect? If the head is not properly ported the gains may be negligible. You appear to be running reasonably large chokes already; and 44IDF may be overkill for what I presume to be a 1.6 street engine. Jetting would always depend on air flow, bigger carbs with bigger chokes need more fuel; and would decrease intake velocity low down; affecting driveability. You may want to consider further tweaking the 40s.....eg better flowing air horns, experimenting with emulsion tubes......etc.
    Hi sorry i was a bit vaug. 1700 forged pistons arp rod bolts.lightened flywheel ballanced with crank/pully.stage 4 race head biggest valves poss.254 cam.twin duplex.steel rocker gear.rolling rd 147bhp but on the limit for twin 40s so obvious option move to 45s but i have aquired a set of genuin matching numbers 44idf webers on a very rare original ford manifold. And yes mainly for the ram effect also space in engine bay.and reducing intake clatter if you know what i meen. Oh and to hopefully get bit more power
    Last edited by Theyellowmex; 20-10-2018 at 15:56.

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    Spanner Monkey djaminhi's Avatar

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    Re: Dcoe to idf

    Ok thats better

    I take it that 147 is at the wheels. not bad.

    So to answer your question....don't expect to use the same jets with more airflow and produce more power; unless you were running rich in the first place.

    I see you mentioned rolling road; fortunately with the dyno at least you can track changes as you play with jetting and chokes etc.
    There is no exact recipe in terms of jet and choke size; as your engine will respond in its own unique way according to the combination of its specs and build. This includes having an efficient exhaust system .....You will have to experiment on the rollers.

    Maybe Others here will offer you a ballpark combination to start with......

    I would say start with your current jetting and choke size and increase the choke size in the first instance, as you check for power gains. I hope you have access to extra chokes......

    BTW

    Have you ruled out your ignition map (or curve) as optimized?

    Your ignition mapping ultimately determines your best power output; no matter how good your fuel delivery.
    Regards,
    Kevin

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    Re: Dcoe to idf

    Quote Originally Posted by djaminhi View Post
    Ok thats better

    I take it that 147 is at the wheels. not bad.

    So to answer your question....don't expect to use the same jets with more airflow and produce more power; unless you were running rich in the first place.

    I see you mentioned rolling road; fortunately with the dyno at least you can track changes as you play with jetting and chokes etc.
    There is no exact recipe in terms of jet and choke size; as your engine will respond in its own unique way according to the combination of its specs and build. This includes having an efficient exhaust system .....You will have to experiment on the rollers.

    Maybe Others here will offer you a ballpark combination to start with......

    I would say start with your current jetting and choke size and increase the choke size in the first instance, as you check for power gains. I hope you have access to extra chokes......

    BTW

    Have you ruled out your ignition map (or curve) as optimized?

    Your ignition mapping ultimately determines your best power output; no matter how good your fuel delivery.
    Thanks again.i have access to jets but not chokes and its the chokes that are expensive to buy and discard.so prob thats my main question

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    Spanner Monkey djaminhi's Avatar

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    Re: Dcoe to idf

    Yeah I know what you mean about expensive

    But the main reason you would go with bigger carbs is more air; which means bigger chokes.....maybe you already have some 36mm chokes on those IDFs

    A good rolling road should have access to chokes. or maybe you could spread the word and someone could loan you......

    I think DCOE and IDF chokes are interchangeable IIRC.

    Don't go changing jets only, without proper consideration to your air correctors and to a lesser extent, emulsion tubes.

    All the best with your tuning; it takes time with carbs....
    Regards,
    Kevin

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