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Thread: What diameter fuel line required for twin carb 4AG conversion?

  1. #1
    Touching Automotive Encyclopaedia Aust162's Avatar
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    Default What diameter fuel line required for twin carb 4AG conversion?

    Thought I'd give the forum a shot on this one. (for old times sake)

    I'd like to know from someone that has a 4AG twin carb (webers or dellortos) powered car as to what fuel line diameter size you are using from the tank to the carbs themselves.

    I remember reading years ago that they should have 8mm (5/16") line. That was what I saw recommended.

    The car is a KE70 Corolla. The steel lines and flex hose in the car are 6mm (1/4") feed size and I believe 4mm return size. This is what powered the old 4KC from factory.

    FWIW the engine is fairly mild. It is a rebuilt 16V with 264 cams, valve springs, headers, etc. (Shouldn't need a crazy amount of fuel supply.)


    Anyone run their 4ag carb car with 6mm IN and 4mm OUT? Did it cause problems? Did you run new lines and increase to 8mm IN?

    Thanks to anyone that might read this!
    *hearts* his 4age powered KE70 Panelvan!
    Hi, Im enthused about corollas..

  2. #2
    Forum Member 1st year Apprentice
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    Default Re: What diameter fuel line required for twin carb 4AG conversion?

    Generally speaking most side draught carbies for use with inline engines use 5/16”, this will of course depend on the carbies you are using? Have you made this decision yet?


    Sent from my iPhone using Tapatalk

  3. #3
    Touching Automotive Encyclopaedia Aust162's Avatar
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    Default Re: What diameter fuel line required for twin carb 4AG conversion?

    Quote Originally Posted by Southern988 View Post
    Generally speaking most side draught carbies for use with inline engines use 5/16”, this will of course depend on the carbies you are using? Have you made this decision yet?


    Sent from my iPhone using Tapatalk
    Yep, the carbies have 5/16" pipe coming off them at the union . I have 40mm dellortos from an Alfa engine.

    Obviously I will run 5/16" (8mm) to connect them, but I am trying to decide whether I feed them with the 6mm steel lines that come from the tank to the engine bay. then step the hose up from 6mm to 8mm just before the carbs.
    *hearts* his 4age powered KE70 Panelvan!
    Hi, Im enthused about corollas..

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