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Thread: Carb question

  1. #1
    Join Date
    Feb 2021
    Posts
    7

    Default Carb question

    i just got my first 604 what carb should i use a 650 or 750 carb? i know a guy who has a used 750 gas carb for sale and another question is what jet and nozzle sizes do i need to start out with in the carb? thanks for any info oh the carb brand is a AED if that matters is this brand a good carb for crates?

  2. #2
    Join Date
    Oct 2007
    Posts
    964

    Default

    750 carbs on gas do not accelerate as well as a 650
    the 750 will make more power past the flagstand but the 650 will get to the flagstand quicker.
    We prefer 650 carbs on our 604 packages when using gas

    It sounds like you are just getting started out here so if the price is fair and the seller is trusted ---It might be a good fit for you----it will be a little lazy on restarts but will be easier to drive under race conditions (especially in the slick)

    as for calibrations---if the seller was using it on a 604 with same fuel you are running and didn't have any issues then just leave it be
    a couple new power valves and a general cleaning is always a good idea

    carburetor builders today use different methods of getting to the correct fuel ratio---
    It's much more than just "jets" --so there is no possible way to tell anyone what jet should be in their carb without knowing much more information.

    as for nozzles---that is about drivability and again there is more that goes into the nozzle recipe than just size of squirter but typically it's between 26 and 31----28 is a good start

    hope that helps
    Brad
    www.race-1.com

  3. #3
    Join Date
    Feb 2021
    Posts
    7

    Default

    if a 750 on gas is a little lazy on restarts what fuel type 750 would eliminate this? what power valve should be used for this? thank you brad for the info.

  4. #4
    Join Date
    Nov 2012
    Location
    Wisconsin
    Posts
    3,094

    Default

    Call AED...
    Member of the Luxemburg Speedway Hall of Fame
    Class of 2019

  5. #5
    Join Date
    Oct 2007
    Posts
    964

    Default

    on 604's we stay away from true 750's except on methanol
    we do use a 725 for E-85
    now that is our opinion ----many people run 750's on gas successfully ---it's just not the way we approach our package

    as for powervalve number---different builders use different rates so I am not sure what your AED actually was designed for---as Krooser said --it might not be a bad idea to give AED a call

    power valves are a carburetor timing device ---the number determines when the mixture richens
    so even if it's supposed to have a 6.5 in it ---going to a 5.5 or 4.5 is not a big deal to get started
    We like to see new powervalves twice per season as they do get "lazy" with fuel exposure

    Brad
    www.race-1.com

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