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Technical Help with tuning carb

Discussion in 'The Hokey Ass Message Board' started by SnakePlissken69, Nov 28, 2019.

  1. SnakePlissken69
    Joined: Oct 24, 2019
    Posts: 56

    SnakePlissken69

    Ok so it's been decades since I had to tune a carburetor or distributor. I've been working on a 64 falcon club wagon (read as Econoline) that sat for a long time and now I'm trying to get it running. I've replaced the fuel pump, replaced points with pertronix solid state ignition, and rebuilt the carb (Holley 1940 w load o matic).

    My symptoms are running very very lean (must have choke partially closed to idle, idle mixture screw backed almost all the way out of the threads) and fast idle. My first thought is vacuum leak, but almost all the lines coming out of it are steel tube, except for 1" of rubber lines just to connect two ends (see pic). Am I on the right track thinking vacuum leak? Any advice on how to find it?

    Oh one other detail. When I pulled the carb appart the old gasket had scorch marks and the accelerator pump was melted. All replaced, nothing seems to have any fire damage, but thought I should share.

    Final question, I know what the line going to the distributor does, but what does the line going to the top of the bore (with the rubber bit) do?
     

    Attached Files:

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  2. SnakePlissken69
    Joined: Oct 24, 2019
    Posts: 56

    SnakePlissken69

    Oh yeah, 170ci 3 speed manual
     
  3. Connect a vacuum gauge to it and see what it has to say.
     
  4. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,497

    gimpyshotrods
    Member

    Check the core plugs at the end of the manifold log. Spray some starting fluid at them, and see if the idle rises.
     
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  5. SnakePlissken69
    Joined: Oct 24, 2019
    Posts: 56

    SnakePlissken69

    What should it say? If it's correct I mean
     
  6. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,497

    gimpyshotrods
    Member

    I think that line on the top cover is a vent for the float bowl. so any vapor does not linger in the doghouse, right next to you.
     
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  7. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,497

    gimpyshotrods
    Member

    If it is a vent, nothing.
     
  8. SnakePlissken69
    Joined: Oct 24, 2019
    Posts: 56

    SnakePlissken69

    That makes sense. There's no vacuum lines from the manifold, should I test it from the spark advance? And if so, what would a good reading be?
     
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  9. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 1,832

    2OLD2FAST
    Member
    from illinois

    Did you clean out the gas tank ? Put an inline filter in the line ? Carb could have sucked a load of crap in that rebuilt carb , or the carb wasn't clean enough ??
     
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  10. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,391

    greybeard360
    Member

    Doesn't look like a rebuilt carb from this end. That usually entails cleaning it inside and out, making sure all of the passages are clear, making sure the float level is correct. I see that at least part of that was not done.... Like the cleaning part.

    Does it have fresh gas in it or are you trying to run on what was left in the tank? Even with a couple of gallons of the old stuff mixed with a couple of gallons of fresh gas isn't going to run right.
     
  11. JackdaRabbit
    Joined: Jul 15, 2008
    Posts: 470

    JackdaRabbit
    Member
    from WNC

  12. You can connect at the spark advance port on the carb to get manifold vacuum if it's below the throttle plate. Normal reading at idle should be a steady 18-20 in. with a stock camshaft. Most vacuum test gauges have a colored band around the face that will tell you if your reading is in the normal range and what could be causing lower than normal readings.
     
    Last edited: Nov 28, 2019
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  13. Boneyard51
    Joined: Dec 10, 2017
    Posts: 3,338

    Boneyard51
    Member

    I hope those pictures were “before” the carb rebuild. If not.......you need to do that job again!






    Bones
     
  14. SnakePlissken69
    Joined: Oct 24, 2019
    Posts: 56

    SnakePlissken69

    Yes everyone these are the "before" photos of the carb haha, sorry I didn't clarify. Just wanted to show what my set up was.

    All new gas, the tank was bone dry.

    I'm ordering a vacuum gauge now, but I'm suspicious about the base gasket so I'm going to throw a slight film of silicon on it and see if it's any different. Will post updates.

    Thanks Everyone, this is a good community
     
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  15. Gasoline will melt your silicone but you might find out if that gasket is leaking before it melts. A quicker test would be to spray some starting fluid around the gasket with the engine idling. If it's leaking the rpms will increase. Spray the fluid around the intake/carb to check for vacuum leaks...its' super easy.
     
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  16. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 1,832

    2OLD2FAST
    Member
    from illinois

    So do you have a fuel filter ?
     
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  17. Wanderlust
    Joined: Oct 27, 2019
    Posts: 56

    Wanderlust

    A dry tank will still have residue and new gas will soften and release it into the system
     
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  18. Truck64
    Joined: Oct 18, 2015
    Posts: 3,853

    Truck64
    Member
    from Ioway

    To add to that generally the higher the #, the better. It's more important that it is a steady needle compared with a specific # but "15 to 22" is so wide a spread as to be pretty much useless without first understanding the reason for the wide variance is because of the effect of altitude on manifold vacuum.

    Keeping in mind a stock engine in good mechanical condition in good tune should pull 18" to 20" at sea level, 16" might be excellent for Denver but would indicate a serious defect of some kind in Omaha, even though the charts say this is "normal". It ain't, 2" to 3" down from what it should be is a whole bunch. So, depending on where you live it's important to already know what are a typically good numbers for a normal engine.

    Engine must pass the vacuum test at normal factory idle RPM and particularly the factory ignition timing spec, i.e. if the ignition timing has to be advanced 10° past the normal factory serving suggestion spec of say 3° or 6° to get good numbers this usually indicates late valve timing, maybe a stretched or worn timing chain set.
     
  19. SnakePlissken69
    Joined: Oct 24, 2019
    Posts: 56

    SnakePlissken69

    5052AB7B-1826-4DB9-AD05-CA30378F2E6E.png

    Yes the fuel pump has a giant cartridge filter
     
    Last edited: Nov 29, 2019
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  20. squirrel
    Joined: Sep 23, 2004
    Posts: 44,258

    squirrel
    Member

    Never use silicone anywhere near the fuel system. Ever. Please.
     
  21. If you are worried about the base gasket leaking, get or make a new one, and make sure the manifold, spacer, and bottom of the carb are spotlessly clean and reinstall. Jim is 150% right, no silicone, RTV, or sealer of any kind in a fuel system. If you used any sealer in your rebuild, take it apart and clean it all out again. Pay close attention to ALL of the internal passages.


    Sent from my iPhone using The H.A.M.B. mobile app
     
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  22. SnakePlissken69
    Joined: Oct 24, 2019
    Posts: 56

    SnakePlissken69

    It's all new gaskets from the rebuild, I just can't think of where else it would be leaking. The intake manifold is cast as part of the head so it can't leak there, there's no vacuum lines coming off the manifold, and iirc the spark advance is above the throttle plate. It's all cleaned up well before the install. Maybe the carb is just beyond salvageable?
     
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  23. squirrel
    Joined: Sep 23, 2004
    Posts: 44,258

    squirrel
    Member

    Did you check the plugs in the ends of the (integral) intake manifold, as suggested? You can spray starting fluid (or carb cleaner) at them or at any other place you suspect a vacuum leak. if there is a vacuum leak there, the engine RPM will change, since it's getting more fuel.
     
  24. Mr T body
    Joined: Nov 2, 2005
    Posts: 2,077

    Mr T body
    Alliance Vendor
    from SoCal

    Check that both the carb gasket and the gasket UNDER the preheater are intact and are correct for the bore and vacuum channel.
     
  25. saltflats
    Joined: Aug 14, 2007
    Posts: 9,709

    saltflats
    Member
    from Missouri

    Does the vacuum advance get manifold vacuum?
     
  26. In the OP's first post I see a reference to "Loadamatic". If this engine was so equipped are you sure that BOTH the carb and the distributor are compatible, Loadamatic units? :confused:
     
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  27. SnakePlissken69
    Joined: Oct 24, 2019
    Posts: 56

    SnakePlissken69

    No it gets vacuum off the carb, and im pretty sure it's above the throttle plate. I'd have to go out and double check
     
  28. SnakePlissken69
    Joined: Oct 24, 2019
    Posts: 56

    SnakePlissken69

    I haven't really. Are you suggesting they corroded to the point where there are rust holes?
     
  29. SnakePlissken69
    Joined: Oct 24, 2019
    Posts: 56

    SnakePlissken69

    Good thought, I haven't even pulled it off. That will be next
     
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  30. SnakePlissken69
    Joined: Oct 24, 2019
    Posts: 56

    SnakePlissken69

    I don't know much about load o matic systems, so I can't give a good answer. As far as I can tell everything looks correct, I believe it is the original carburetor. I tried to post photos that may help someone who knows more about it than I. But even if it wasn't, wouldn't it still work correctly at idle (no advance from vacuum) ?
     
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