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Carb Question

Discussion in 'Technical Q&A' started by jimshadow, Apr 13, 2009.

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  1. jimshadow

    jimshadow F1 Veteran
    Lifetime Rossa Owner

    Feb 19, 2006
    6,255
    Indiana/North Carolina
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    JIM
    #1 jimshadow, Apr 13, 2009
    I had my carbs rebuilt last year right before I drove the GT4 to Mississippi. It was essentially put up for the winter after that and was only driven once or twice for very short distances until last week when I took a 3hr drive in it. I noticed a slightly stronger gas/oil smell than normal (my wife and kids say my car 'stinks. :) )
    Well, as I looked at the manifold/carb bases, I noticed that atleast 2 are leaking. :( I called the shop that did it and they said , "No problem, bring it right back in and we'll make sure its right." The mechanic mentioned that the "Float levels may be set too high".
    My question is: Would this cause a carb to leak? Though I can do most everything mechanically on my car, I can't do the carbs, nor do I want to at this time. I will someday, but there is enough other projects to keep me busy.
    I'm curious about this. Could someone please explain. (Yes, the entire carbs were rebuilt including the base gaskets, which is where I *think* they are leaking from though I can't get a good look in there without taking stuff apart. )

    JIM
     
  2. 2NA

    2NA F1 World Champ
    Consultant Owner Professional Ferrari Technician

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    #2 2NA, Apr 13, 2009
    Last edited: Apr 13, 2009
    If floats are set too high the engine will typically flood easily and run too rich. It is possible for them to overflow but usually most of the gas goes inside the motor not outside. There are a few places a fuel leak can come from but the base gasket isn't usually one of them. There you will sometimes see a vacuum leak but not liquid fuel.

    I would check the needle valves. They can catch a piece of dirt or get sticky during storage causing a carb to flood.

    You are describing one of the most common Springtime problems for cars that are stored during Winter.
     
  3. yelcab

    yelcab F1 World Champ
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    #3 yelcab, Apr 13, 2009
    Jim

    Second on the Needle Valves. Next thing you notice is your exhaust glows red in the night, then your car really stinks when it burns to the ground.
     
  4. jimshadow

    jimshadow F1 Veteran
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    #4 jimshadow, Apr 13, 2009

    Thanks for the replies! I got it into the shop quickly so it doesn't burn to the ground! :)

    The car is "stored" right in my garage and gets started occasionally and moved around when its dry out, however, this year is sat for a very long time as we had tons of snow/wet weather. Last week was the first time that I really drove it.
    We'll see what they say. I left the car there today and will pick it up on Thurs. :)

    JIM
     
  5. Martin308GTB

    Martin308GTB F1 Rookie

    Jan 22, 2003
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    Martin N.
    #5 Martin308GTB, Apr 14, 2009
    Last edited by a moderator: Sep 7, 2017
    Hello from Germany,

    when they have ultrasonic cleaned the carbs during the recent rebuild and didn't restake the lead plugs after that, you might have loose lead plugs.
    There are some just above the base gasket which can lead to the mistake, that the fuel comes out of the base. This happens all the time.

    Mine were leaking too - without ultrasonic cleaning - and I restaked all lead plugs after my rebuild....... dry carbs.

    Best Regards

    Martin
    Image Unavailable, Please Login
     
  6. tomoshea

    tomoshea Formula Junior

    Dec 29, 2003
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    Tom O'Shea
    #6 tomoshea, Apr 14, 2009
    Jim

    Had the same problem on one of my carbs, thought it was a leak thorugh the base gaskets, turned out the lower lead bead in the photo above started to weep, common enough apparently, and occurred after a full rebuild and clean of the carbs.

    Mine was fixed with a small drop of epoxy over the lead plug (didn't want the hastle of another engine strip). No leak since the epoxy and a much reduced petrol smell. Fuel efficicency has improved also :)
     
  7. Irishman

    Irishman F1 Rookie

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    #7 Irishman, Apr 14, 2009
    Okay I will put my ignorance out there. I have rebuilt the carb on my Harley but have not touched the 308. What is the lead plug?
     
  8. 2NA

    2NA F1 World Champ
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    #8 2NA, Apr 14, 2009
    During manufacture there are passages that are cross-drilled to effectively allow flow around corners. It is necessary to block some of the openings and frequently lead plugs are inserted and "peened" in place (sort of like a filling in a tooth). Occasionally they become loose and begin to leak.
     
  9. chrismorse

    chrismorse Formula 3

    Feb 16, 2004
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    chris morse
    #9 chrismorse, Apr 14, 2009
    The first thing that comes to mind is the possiblility of a fuel hose leak, either through a cracked hose or insufficiently tightened clamps. Either the accelerator pump body, the cold enrichment device, or the carb top could also be loose/have a bad gasket. Excessive fuel pressure could also be causing a bit of a weep.

    Untill you are absolutely sure it has been fixed, if you must drive it, have a big Halon extinguisher at yoru side.

    a few years ago, I also had some soft, wet, spongy original hoses that had fuel coming through the fabric.

    Good luck,
    chris
     
  10. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    #10 snj5, Apr 14, 2009
    +1

    It also may be as simple as a hose or hose clamp weeping. I'm sure you've taken off the air box - what I do is start it and just watch it run, feeling the hose connections, gaskets, etc. Also ensure that your enrichment device levers are all full off.

    A common cause of leaking is a stuck float and/or needle valve. If it is not uber-simple like a hose or gasket weeping, this would be my bet.

    Good luck
     

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