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Technical Help me get My Holley 390 carb to idle correctly

Discussion in 'The Hokey Ass Message Board' started by 19Fordy, Dec 20, 2018.

  1. 19Fordy
    Joined: May 17, 2003
    Posts: 7,517

    19Fordy
    Member

    I have a Holley 4160 390CFM 4bbl carb with vacuum secondaries on my
    1959 Ford 292 Y Block standard shift vehicle. I started the engine and the engine had it's usual curb idle of about 750 RPM. There is an inline filter at the carb and a filter mounted at the gas tank before the electric fuel pump.

    Then, I shut it off and added some antifreeze. Restarted the engine and now the engine
    won't idle unless the curb idle is around 1100 RPM. I did not do anything else to the engine and
    never touched the carb. I don't think the anti-freeze has any bearing on the problem.

    I don't want to start taking the carb apart without first having some idea about what might be causing the problem. The carb is about 10 years old and has always run great both at curb idle and on the road.

    Any suggestions and info. are very much appreciated. Thanks.
     
    chryslerfan55 likes this.
  2. Boneyard51
    Joined: Dec 10, 2017
    Posts: 5,573

    Boneyard51
    Member

    Did it back fire through the air cleaner? Might have blown the power valve. Could have developed a leak in the float if it has brass floats. Check your float level.



    Bones
     
    porknbeaner and chryslerfan55 like this.
  3. Aaron65
    Joined: Dec 29, 2005
    Posts: 313

    Aaron65
    Member
    from Michigan

    You might want to check to see if the secondaries might have somehow gotten stuck open a touch, although it seems unlikely considering you didn't touch the carb.
     
  4. squirrel
    Joined: Sep 23, 2004
    Posts: 50,927

    squirrel
    Member

    I think what he meant, is that if he lets off the throttle, it dies. He has to keep it above 1100 rpm to keep it running, because it dies at idle.
     
    upspirate and chryslerfan55 like this.

  5. oldiron 440
    Joined: Dec 12, 2018
    Posts: 2,822

    oldiron 440
    Member

    Do you have white smoke in the exhaust?
     
  6. rjones35
    Joined: May 12, 2008
    Posts: 865

    rjones35
    Member

    Maybe coincidentally a filter got a little plugged up just then, or a piece of dirt managed to get stuck in a passage in the idle circuit, or idle mixture screws could have vibrated out a little, just enough to mess with things.
     
    Deuces and Truck64 like this.
  7. Truck64
    Joined: Oct 18, 2015
    Posts: 5,316

    Truck64
    Member
    from Ioway

    That don't mean a new Pope either. Head gasket? Is coolant disappearing why you're adding anti-freeze?
     
    Clay Belt likes this.
  8. catdad49
    Joined: Sep 25, 2005
    Posts: 5,569

    catdad49
    ALLIANCE MEMBER

    Sounds like some dirt got in there, doesn't take much.
     
  9. tinkirk
    Joined: Jan 16, 2017
    Posts: 111

    tinkirk

    Vacuum leak


    Sent from my iPhone using Tapatalk
     
    sunbeam and porknbeaner like this.
  10. Rickybop
    Joined: May 23, 2008
    Posts: 7,876

    Rickybop
    Member
    from Michigan

    Did the idle go up by itself? Or would it just not stay running at idle and you adjusted it higher?
    I've inadvertently pulled off a vacuum hose while working under the hood. Starts idling higher. When you rev it, the rpms hover before settling down.
    If not, I'd agree about debris in the carb being a likely suspect. If that's the case and it's starving for fuel, it might have a tendency to "pop" or hesitate a little under acceleration and cruise speed. It might pop pretty good on deceleration too.
     
  11. Rickybop
    Joined: May 23, 2008
    Posts: 7,876

    Rickybop
    Member
    from Michigan

    Hopefully not related to adding antifreeze. Then I'd say head gasket as others suggested.
     
  12. 6sally6
    Joined: Feb 16, 2014
    Posts: 1,894

    6sally6
    Member

    Try the shade tree tune up! Get it running and then pull the throttle wide open AND quickly clamp your hand over the top of the carb. When it almost dies...remove your hand and let it start to speed up again and clamp your hand on top of it again.
    It pulls a tremendous amount of vacuum thru the carb and "sometimes" that will clear out the trash.
    Won't hurt anything unless you go to sleep and let the durn thing over rev...float the valves...throw a rod through the side of the engine...make you bang your head on the bottom of the hood..something-like-that!
    6sally6
     
    Terrible80 and Boneyard51 like this.
  13. I've had enough power valve problems with Holley 4 barrels to make that my first thought. It could be crap caught in the idle circuit too. If you don't like 6sally6's method you can pull the idle mixture screws out and blow the idle circuit clear with compressed air. You're gonna have to readjust the mixture when you're done though, maybe a good idea anyway. Both methods work with varying success.
     
  14. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,993

    2OLD2FAST
    Member
    from illinois

    The carb is 10 years old and it's acting up and your bitching , clean it ,put a kit in it , add a power valve protector, and be glad you got 10 years out of it ,. Sheeeeesh !
     
    Boneyard51 likes this.
  15. 19Fordy
    Joined: May 17, 2003
    Posts: 7,517

    19Fordy
    Member

    I am not complaining and I am glad it lasted 10 years. No need to get nasty!
    Working on a car in the bitter cold is not fun as you get older.

    I do thank all who responded for their help.
     
    Truck64 likes this.
  16. scoop
    Joined: Jul 4, 2001
    Posts: 1,353

    scoop
    Member

    You're from Florida,whats bitter cold to you?
     
    Bugguts likes this.
  17. upspirate
    Joined: Apr 15, 2012
    Posts: 2,294

    upspirate
    Member

    65 or below for me.......Although we did go sailing earlier this week when it was 65
     
    rjones35 likes this.
  18. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,993

    2OLD2FAST
    Member
    from illinois

    Bitter cold in coral springs Fla .? You're joking , right? NJ. ROFLMAO ! Waaaaaa , Waaaa
     
    Truck64 likes this.
  19. 19Fordy
    Joined: May 17, 2003
    Posts: 7,517

    19Fordy
    Member

    Nope. I knew someone would think that. It's my brother's car in upstate NY. Since he is not good at posting things on the computer I was asking for him. Then I email him the HAMB link and he can open it. Hope that not against the HAMBurger Code of Justice.
    By the way, thanks again for the replies. I am sure he will benefit. Merry Christmas to all.
     
    upspirate likes this.
  20. flatjack
    Joined: Feb 13, 2007
    Posts: 948

    flatjack
    Member

    Lighten up, dude. My carb has been on for over 20 years without a problem. Haven't touched it. Shouldn't have to.
     
  21. scoop
    Joined: Jul 4, 2001
    Posts: 1,353

    scoop
    Member

    Understood,I would pull the carb,got to be some crap in there.Have a Merry Christmas!!
     
  22. scoop
    Joined: Jul 4, 2001
    Posts: 1,353

    scoop
    Member

    I'd love to see 65,probably won't till late April!
     
    upspirate likes this.
  23. scoop
    Joined: Jul 4, 2001
    Posts: 1,353

    scoop
    Member

    Do you drive it?Hahaha
     
  24. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,993

    2OLD2FAST
    Member
    from illinois

    When's the last time it had gas in it ?
     
  25. flatjack
    Joined: Feb 13, 2007
    Posts: 948

    flatjack
    Member

    Funny man. I've got about 60, 000 miles on the car.
     

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