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Technical Carburetor adapter question

Discussion in 'Traditional Hot Rods' started by AGELE55, Aug 17, 2021.

  1. AGELE55
    Joined: Jan 4, 2018
    Posts: 398

    AGELE55
    Member

    I have an edlebrock spread bore intake and an edlebrock 650 cfm square bore carb. I see al lot of adapters , but seriously, the carb seats well with no air gaps. Is the adapter necessary?
     
  2. Does the linkage work good all the way to wide open?
     
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  3. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,833

    greybeard360
    Member

    I have seen quite a few spread bore intakes leak with square bore carbs at the outside edges of the secondaries. They do make a flat plate to use under the carb so you can use a spread bore gasket on the bottom and square bore gasket on to.
     
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  4. acme30
    Joined: Jun 13, 2011
    Posts: 195

    acme30
    Member
    from Australia

    Are you positive the square bore carb fits perfectly with good overlap on the spread bore manifold?

    Not sure about the edlebrock carb but my experience with a Holley square bore was that there is one section where the carb only just barely mates / overlaps with the manifold.

    When you first put them together all is fine but eventually as there is only minimal contact surface the gasket sucks in and you have an air leak. Which can be troublesome to find as it is under a part of the carby you can't easily see.

    Perhaps edlebrock corrected this with their design but worth a second look and explains why you need an adaptor with some setups
     
    Last edited: Aug 18, 2021
    gimpyshotrods and AGELE55 like this.

  5. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,185

    Mr48chev
    Member

    Last edited: Aug 17, 2021
  6. I'm with @greybeard360 , flat plate(gasket sized) to seal off the thin sealing surface. I don't even think it's .125" thick.
     
  7. squirrel
    Joined: Sep 23, 2004
    Posts: 50,195

    squirrel
    Member

  8. AGELE55
    Joined: Jan 4, 2018
    Posts: 398

    AGELE55
    Member

    Algoma56 likes this.
  9. Thomas K.
    Joined: Dec 25, 2018
    Posts: 28

    Thomas K.
    Member

    My sbc had a 1406 Edelbrock on a spreadbore intake with an open adapter on it. Troubleshot a vacuum leak and found the adapter was not sealing completely to the intake. Installed a 4 hole adapter recommended by Edelbrock and problem was solved.
     
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  10. AGELE55
    Joined: Jan 4, 2018
    Posts: 398

    AGELE55
    Member

    So as I’m looking into this, I figured I would buy a spread-bore to square bore adapter made from phenolic or similar material to reduce heat transfer to the carb. Oddly enough, I can’t find one. They’re all aluminum, or steel. Anybody seen one....ever?
     
  11. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,185

    Mr48chev
    Member

    I've never seen one, you would have to get one that fits either the carb or the intake and then use the plate that Jim posted the link to in post 7. You should be able to get one of those plates off the speed trinket wall at any O'Reilly's as they are a really common item. Worse case they can get one in on the next truck from the warehouse. Just about everyone who has put an Edelbrock carb on a Q jet intake has one laying around but sometimes they don't let the linkage clear the manifold such as on a cast iron Cad 425/472 or 500 intake.
     
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 50,195

    squirrel
    Member

    Carb flange adapters need to have some strength....phenolic spacers work because they're just under compression. So it doesn't surprise me that you can't find one.
     
  13. AGELE55 likes this.

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