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Technical Edelbrock 500, Holley 390, or Carter AFB?

Discussion in 'The Hokey Ass Message Board' started by Mr. C., Oct 25, 2020.

  1. Hi folks. I have a Flathead Ford with an Edelbrock 500 4BBL. It was running okay, but I'm aware that the vast majority of people will say it's too big for the engine.
    As the engine is now in bits for a re-build, maybe it's time for a re-think.
    A) Would the 500 Edelbrock be a good performer IF it were correctly jetted to suit on a rolling road?
    B) Would buying a 390 Holley be a better choice?
    C) I already have a Carter AFB Performance Series carb here, what's the CFM rating of these? (Remember these, the one with the badge across the front "Carter AFB Performance Series" popular about 25 years ago?).

    For info, my inlet manifold is an Offenhauser and currently has an adapter plate for the Edelbrock. (Would an Edelbrock inlet be better?)
    Engine spec is:
    8BA, +.125, 4" crank
    Isky Max-1 cam
    Edelbrock heads
    Aluminium flywheel
    MSD distributor
    Fenton headers
    Block is currently stock but will be getting ported, polished, & relieved, plus the inlet & exhaust will be port matched.
  2. dan c
    Joined: Jan 30, 2012
    Posts: 2,297

    dan c

    rule of thumb on flathead carburetion is to multiply cubic inches by .75. the 390 is the smallest you mention, but a tad big, but it's ok because it runs on primaries most of the time.
  3. The Carter Competition series carbs were usually 625 cfm. 'Ol Ron, (Ron Holleran) flathead guru, Likes both the 500 cfm Edelbrocks and the Holley 390-450 cfm. He has also used the old Rochester $ jet carburetors with great success. Check out 'Ol Ron on the Fordbarn.
  4. 2935ford
    Joined: Jan 6, 2006
    Posts: 3,684


    I've used 390 on two mild built flatties..........both ran great!

  5. lemondana
    Joined: Feb 21, 2009
    Posts: 152

    from Lincoln NE

    Carter made a 400 years ago. They are still floating around here and there.
    LAROKE and JeffB2 like this.
  6. lemondana
    Joined: Feb 21, 2009
    Posts: 152

    from Lincoln NE

    The number for the Carter 400 is the 9000 Series AFB's is 9400.
    Nailhead Jason likes this.
  7. gimpyshotrods
    Joined: May 20, 2009
    Posts: 19,209


    The Edelbrock will be fine. The secondaries are on-demand. The primaries are smaller than the secondaries.

    Once it is set up properly, the engine will use only what it needs.

    Your existing manifold is fine.
    dan c and loudbang like this.
  8. wheeltramp brian
    Joined: Jun 11, 2010
    Posts: 1,230

    wheeltramp brian

    I believe I have a Carter 400 in my pile,if interested I can dig it out
  9. Mike VV
    Joined: Sep 28, 2010
    Posts: 2,485

    Mike VV
    from SoCal

    Beware, a "good" (clean, tight throttle shafts, all of the correct parts) Carter AFB will cost a small fortune. I know, I looked into a 400cfm Carter this summer. I went with the Holley.
    I'd go with the Holley 390.

    dan c likes this.
  10. Carter also made a 500, best to check the number on the front and find out that it is.
  11. Thanks, would you happen to know the size of the Edelbrock 500 primaries compared to those of a Holley 390?
    The secondaries on mine may have never opened!
  12. saltflats
    Joined: Aug 14, 2007
    Posts: 11,074

    from Missouri

    390 Holley and the Carter 500 have the same size primary throttle valve.
  13. The 390 would be a better choice, I switched out the holly on my flathead and was much happier with the performance. HRP
  14. What did you replace?
  15. I had a Holley 600 cfm carburetor and it was definitely overkill., the 390 was much better and the car just ran better around town and out in the interstate. HRP
  16. no55mad
    Joined: Dec 15, 2006
    Posts: 1,897


    At a sidebar swapmeet meeting, a 2 barrel carb off an early Mustang V8 was recommended.
  17. tubman
    Joined: May 16, 2007
    Posts: 5,913


    I really like a Rochester small base 2G on a bored out late Mercury manifold on street driven cars with a hood. I believe they are the equivalent of 275 cfm (about the same as 2 97's or 94's).
  18. gimpyshotrods
    Joined: May 20, 2009
    Posts: 19,209


    Edelbrock 500:
    Primaries: 1-7/16"
    Secondaries: 1-11/16"

    Holley 390:
    All: 1-7/16"

    Have you confirmed that the throttle blades are indeed opening on the secondaries (linkage intact)?

    Are the metering flaps over the secondaries moving freely?
    Mr. C. likes this.
  19. Gimpyshotrods - The linkage is intact, I was just musing that the engine may not have been flowing enough air to make the secondaries open even at wide open throttle.

    Hotrodprimer - I'm not surprised you saw benefits from swapping a 600 for a 390. The Edelbrock 500 does seem a lot more 'forgiving' on a smaller engine than a 600 Holley, more than it's 100cfm difference would suggest.
  20. Normant93
    Joined: Apr 23, 2009
    Posts: 148


    I'd be interested if he's not.
  21. goldmountain
    Joined: Jun 12, 2016
    Posts: 3,182


    My friend Bill had a 390 Holley that was too much for his slant six so he used it on the 350 Chev in his '40 Dodge. Worked great.

    Sent from my SM-T350 using The H.A.M.B. mobile app
  22. jimmy six
    Joined: Mar 21, 2006
    Posts: 10,295

    jimmy six

    Consider a small base Rochester 4GC or Carter WCFB off any early to mid 50’s GM or Mopar. They bolt directly on the manifold and have the correct jetting for your compression.
  23. dan c
    Joined: Jan 30, 2012
    Posts: 2,297

    dan c

    they work great; ran one on an offy 4bbl intake with an adapter!
  24. The thing is, being in Britain I'm a little bit limited when obtaining the carbs you've suggested. That's why I boiled the choices down to those three. I already have the Edelbrock & Carter, and I can easily buy a 390 Holley.
  25. gimpyshotrods
    Joined: May 20, 2009
    Posts: 19,209


    If you are only truly running on the primaries of an Edelbrock 500, then neither switching to a Holley 390, not a Carter will make a difference.

    You will still just be on the primaries, and your wallet will be thinner.
  26. 6sally6
    Joined: Feb 16, 2014
    Posts: 1,799


    Do the Eddy....
    I already HAVE it..........UR putting it on a fairly 'modified' engine. And like stated above with the vacuum secondaries it will use just what it can suck.
    A "trick" I have done to my Eddy carb you might wanna try......the air flapper on the secondaries has a counterweight on it to keep it in the shut position. As the engine 'needs' more air/fuel the air flap slowly pulls open so as to prevent a bog when the secondaries come open.
    Real simple and effecient set-up.
    Naturally I can't leave well enough alones soooooo...... remove the flapper and drill a small hole in the counterweight(making it lighter). This lets it open 'quicker' when the engine is needing it. It let's the engine sorta come alive in a hurry. A lot like an A/T down shifting into second gear!
    Pull-it-out-and-play-with-it but...
    DO NOT take too much weight out of the counterweight! Then IT WILL bog when the secondaries open. Just do a little at the time.
    It gives me a big-stupid grin when ever I floor the pedal. (never fails!)
    saltflats and gimpyshotrods like this.
  27. gimpyshotrods
    Joined: May 20, 2009
    Posts: 19,209


    Yup, all that.
  28. Makes sense, If the primaries on both the Holley & the Eddy are the same. Of course, when (or if) the secondaries open I imagine the Holley might be better. The other thing is a rolling road I planned to use has Holley jets in stock whereas I'd need to source one of those comprehensive, and expensive tuning kits for the Eddy.
    Thanks for the responses, food for thought indeed.
  29. Corrected!
    Last edited: Oct 28, 2020
  30. 19Fordy
    Joined: May 17, 2003
    Posts: 7,388


    Keep in mind the 4 barrel OFFY intake offsets the generator and fan pulley 7/8 inches
    towards the drivers side of engine.

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