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Technical Carb problem

Discussion in 'Traditional Hot Rods' started by Joseph Allen, Aug 27, 2018.

  1. Joseph Allen
    Joined: Nov 22, 2016
    Posts: 187

    Joseph Allen

    Hi I’m running a 364 nailhead with four big 97 Stromberg s , fuel pressure set at 2/1/2, seem like I’m getting way to much fuel in the manifolds, fouling out the plugs, I disconnected the back two carbs and I’d running better, I have them leaned out two 3/4 turn, do I need to rejet all of then , I believe jet size is 45. How much should downsize, any help would be much appreciated.[​IMG][​IMG]


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  2. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 31,175

    Jalopy Joker
    Member

    how long have you been running this set up? always had this problem? have a pressure regulator? if so, what is it set at?
     
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  3. czuch
    Joined: Sep 23, 2008
    Posts: 2,688

    czuch
    Member
    from vail az

    Cant help, but, that's a bitchen car.
     
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  4. saltflats
    Joined: Aug 14, 2007
    Posts: 12,592

    saltflats
    Member
    from Missouri

    Can you get a manifold vacuum readings?
     
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  5. Joseph Allen
    Joined: Nov 22, 2016
    Posts: 187

    Joseph Allen

    This all completely new, built it from the ground up ... yes I have a regulator and is set at 2 1/2


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  6. Joseph Allen
    Joined: Nov 22, 2016
    Posts: 187

    Joseph Allen

    Yes but not since I disconnected the back two carb , I’m going to check it again today...


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  7. Joseph Allen
    Joined: Nov 22, 2016
    Posts: 187

    Joseph Allen

    Thank you, I have all the fenders for it , going to run it like this for awhile


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  8. tubman
    Joined: May 16, 2007
    Posts: 6,913

    tubman
    ALLIANCE MEMBER

    The manifold looks homemade to me. Has it ever been used successfully on another engine or car?
     
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  9. Joseph Allen
    Joined: Nov 22, 2016
    Posts: 187

    Joseph Allen

    Those are Martin manifolds that got from Buick rodder out of California


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  10. deathrowdave
    Joined: May 27, 2014
    Posts: 3,518

    deathrowdave
    ALLIANCE MEMBER
    from NKy

    The problem is no heat in intake . When you drop pressure , across the throttle plates it wants to ice . Makes the fuel mixture droplets instead of making a vapor from the fuel. If you were running WOT , you wold love it .
     
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  11. tubman
    Joined: May 16, 2007
    Posts: 6,913

    tubman
    ALLIANCE MEMBER

    Please excuse my ignorance. I have had no experience with nailheads, so I don't know anything about "Martin manifolds". So I will ask again, have they been run successfully on another car or engine? I would expect they were, but it would be good to know for sure so we can eliminate that as the potential problem.
     
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  12. AHotRod
    Joined: Jul 27, 2001
    Posts: 12,216

    AHotRod
    Member

    If the plugs are black it's to rich.
     
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  13. Joseph Allen
    Joined: Nov 22, 2016
    Posts: 187

    Joseph Allen

    Yes they have , I’ve seen six twos run on these manifolds. I’m thinking I need to get smaller jets for them ?


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  14. Joseph Allen
    Joined: Nov 22, 2016
    Posts: 187

    Joseph Allen

    What’s wot?


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  15. joel
    Joined: Oct 10, 2009
    Posts: 2,467

    joel
    ALLIANCE MEMBER

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  16. Joseph Allen
    Joined: Nov 22, 2016
    Posts: 187

    Joseph Allen

    Yes I’m sure I would love it , unfortunately the speed limit is 45 on my island


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  17. 28 Ford PU
    Joined: Jan 9, 2015
    Posts: 464

    28 Ford PU
    Member
    from Upstate NY

    Check your float levels if all is good bottom all you idle mix screws then bring them back out only a half turn not 1 1/2 like it calls for on a single carb set up.


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  18. Joseph Allen
    Joined: Nov 22, 2016
    Posts: 187

    Joseph Allen


    Thank you I did check the float levels 1/2 inch from the top, I have the mixture screws at 3/4 turn . Car running pretty good since I disconnected the back two carbs, but would like to run them all, ordered smaller jets , hoping that will work ?


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  19. 28 Ford PU
    Joined: Jan 9, 2015
    Posts: 464

    28 Ford PU
    Member
    from Upstate NY

    With it running look down the throat of each carb and see if you see any of them dumping fuel.


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  20. tubman
    Joined: May 16, 2007
    Posts: 6,913

    tubman
    ALLIANCE MEMBER

    I hate to be a pest, but have you seen this particular manifold running on another car or engine? You say you saw one that ran with six carbs, but it was obviously not this particular manifold , since it has provisions for just four carburetors.
     
  21. 28 Ford PU
    Joined: Jan 9, 2015
    Posts: 464

    28 Ford PU
    Member
    from Upstate NY

    I'm assuming your trouble shooting running rich is at idle?

    If so swapping jet size won't do anything for ya.


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  22. saltflats
    Joined: Aug 14, 2007
    Posts: 12,592

    saltflats
    Member
    from Missouri

    I would get a vacuum gauge on it and set the ignition for the best reading, then adjust from there.
     
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  23. Joseph Allen
    Joined: Nov 22, 2016
    Posts: 187

    Joseph Allen

    Hmmmm! I’m not sure it’s running rich at idle , and I also figured out today the air cleaners were restricting the airflow to the carbs and flooding it out under load


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  24. Sheep Dip
    Joined: Dec 29, 2010
    Posts: 1,572

    Sheep Dip
    Member
    from Central Ca

    I think deathrowdave has your answer.
     
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  25. Joseph Allen
    Joined: Nov 22, 2016
    Posts: 187

    Joseph Allen

    Yes but how do I fix it ?


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  26. carbking
    Joined: Dec 20, 2008
    Posts: 3,715

    carbking
    Member

    I would suggest trying a hotter thermostat. Not sure it will solve the issue, but inexpensive, and certainly will not hurt.

    You need to hook up a temporary tachometer to determine the RPM where you are having issues. Circuits vary, but ballpark:

    Idle <900 RPM
    Transition 750~1200 RPM
    Main 1100 RPM and higher.

    Note the circuits overlap.

    While heat is probably the definitive answer, a possible "Band-Aid" might be in slightly leaning the circuit in play during the issue.

    And while you have your regulator dialed at 2 1/2 psi, maybe hooking up a fuel pressure gauge as a check might be beneficial. Those regulators are about as reliable as the weather forecasts were when I was a youngster ;)

    Jon.
     
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  27. Rattle rod
    Joined: Apr 11, 2016
    Posts: 20

    Rattle rod
    Member

    best advice I can offer is to talk to Clive at Stromberg or Uncle Max at 97express.

    I emailed them both for tips on tuning up my stromberg 6x2 setup. both guys were very helpful and knowledgeable.

    I'm still learning more about how to dial it in, but their combined advice was a good start for my application.
     
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  28. Joe Lemay
    Joined: Nov 28, 2010
    Posts: 106

    Joe Lemay
    Member

    Can only lend you some advice that saved years of guessing.
    Look in Summit for an Innovate fuel/ air mixture meter. Run you about $200. Will tell you exactly what circuit and when your loading up.
    One more piece of advice, DON'T mount permanently, save as a tool for future projects

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  29. Joe Lemay
    Joined: Nov 28, 2010
    Posts: 106

    Joe Lemay
    Member

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  30. Truck64
    Joined: Oct 18, 2015
    Posts: 5,325

    Truck64
    Member
    from Ioway

    It's possible for a carb to run a lean idle yet pig rich at cruise, and vice versa too. The jets don't really factor at idle, etc. The porcelain "color" is just a part of what to look at. Deep down inside the plug where it meets the metal shell is the color indication of lean or rich AFR at wide open throttle. Heat range and ignition timing indicated on the ground electrode. Modern gasoline doesn't color very much either, if plugs are black and sooty with today's fuel, the mix is WAY rich!
     
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