Holly or Edelbrock?

Discussion in 'Ranchero Tech Help' started by Sophie948, Apr 18, 2017 at 5:13 PM.

  1. Kiwirancher

    Kiwirancher In First Gear

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    3
    Don't know if this will help or confuse but I have fitted a 625 Street Demon with the composite bowl to my stock 289 powered 66 .[ $316.00 from Summit ]. Went real well straight out of the box but a bit rich. Fitted the next size up metering rods and went one size down on the jets. Had it analyzed before and after and O2 readings are near perfect. Starts , runs both town and highway really well with better throttle response. It is on a Weiand Street Warrior manifold. My nearest parts store is Summit in the US , only takes a week or two to get bits to NZ !!
     
  2. 5.0 Chero

    5.0 Chero MODERATOR Staff Member

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    12,678
    Location:
    Prunetucky California
    More form Carb doctors

    The Carter AVS (Air Valve Secondary) is a refinement of the basic AFB design. Whereas the AFB used a velocity valve, which is a counterweighted flap below the secondary venturi, the AVS used an air valve, which is a spring loaded flap above the venturi. The purpose of the two is similar, but the air valve is adjustable from outside the carb.

    When the throttle is opened so that the secondary throttle plates begin to open, vacuum develops under the air valve, slowly pulling it open. In this way, the air flow is controlled and the mixture is kept from getting too lean if the throttle is opened suddenly.

    Carter AVS carbs appeared in 1966 on the 275 HP version of the Chevrolet 327, but were never again used on Chevies after that. AVS carbs were found mostly on Mopar applications from 1968-1971. The most sought-after AVS carbs are the 800 cfm models found on 440 CID motors.

    Recently, Edelbrock has been marketing the Thunder Series AVS carburetor, again reproduced by Weber USA.

    Carter did not build a performance version of the AVS after OEM production in the 1971 model yea
     
  3. Hillbilly

    Hillbilly In Maximum Overdrive

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    4,722
    Location:
    Winchester, TN.
    Carl, my 1963 Sport Fury with the 426 Max Wedge came with two 750 cfm AFB carbs. Had no choke horns or plates and relied only on the accelerator pumps for cold starts. Researched the numbers and found they were really the original carbs that came on that engine. Still perform flawlessly after all these years.
     
  4. ribald1

    ribald1 In Maximum Overdrive PLATINUM MEMBER

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    16,091
    Location:
    California
    If you let your engine warm up before driving off (as one is supposed to do), there isn't much need for a choke.
     
  5. handy_andy_cv64

    handy_andy_cv64 In Maximum Overdrive SILVER MEMBER

    Messages:
    4,598
    Location:
    Everett, WA
    All a choke does is make a car start and run easier when dead cold. And when it's dead cold, it needs a rich AFR and a higher engine speed. Even using a manual choke is preferable to sitting like a dummy, holding the engine speed up till it can idle on its own. Dennis' AFBs don't have choke flaps simply to smooth air flow into the venturis because the engine and car are (supposed to be) strictly hi-po, not a grocery getter/errand runner.
     
    cbolt likes this.
  6. Sophie948

    Sophie948 In Fourth Gear

    Messages:
    339
    A choke serves another purpose, too: If you've got a vacuum leak where the throttle rod enters the carb body, giving it more choke and setting the fast idle a bit higher keeps the engine from killing before the carb has warmed up enough that expansion of the carb body seals the leak. Mickey-Mouse temporary fixes are my specialty.
     

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