OT: Mystery hole in bottom of up-draft carb - Page 2
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  1. #21
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    Quote Originally Posted by Ziggy2 View Post
    A lot of the updraft carbs were on tractors or other industrial applications without fuel pumps. In these applications it was very common to put the fuel tank above the engine elevation. If you had a full tank of gas, a stuck float valve, and a plugged carb drain with an intact air cleaner hose to the carb, it was not uncommon to see or hear of a hydraulic lock due to gas filling a cylinder that was in the intake stroke.
    with updraft, the inlet would have to go up above the manifold, so that the gas would not just drain out the intake and air cleaner.

    Could happen, not a biggie as to possibility in many because of the inlet configuration. The hole is a good idea, and the porous plug is also, because the hole would let unfiltered air in after the air filter. Briggs just put in a small hole and let the engine take its chances..

    I've had small engines do that, usually it just drains down the ring gaps into the crankcase. That's worse in some ways, as the diluted oil lets the big ends wipe, maybe permits scoring by the rings, etc. Those were always with a side draft.

  2. #22
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    Quote Originally Posted by Ziggy2 View Post
    A lot of the updraft carbs were on tractors or other industrial applications without fuel pumps. In these applications it was very common to put the fuel tank above the engine elevation. If you had a full tank of gas, a stuck float valve, and a plugged carb drain with an intact air cleaner hose to the carb, it was not uncommon to see or hear of a hydraulic lock due to gas filling a cylinder that was in the intake stroke.
    Stuck float somehow make the fuel flow up the venturi ?

    I have a couple of updraft carbs on various Wisconsin engines. Bobcat with a Ford 1.6l as well.

    No way will an overflowing float bowl flow up the venturi into said engine that I can see.

  3. #23
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    Quote Originally Posted by digger doug View Post
    Stuck float somehow make the fuel flow up the venturi ?

    I have a couple of updraft carbs on various Wisconsin engines. Bobcat with a Ford 1.6l as well.

    No way will an overflowing float bowl flow up the venturi into said engine that I can see.
    We are talking specifically about an IHC gas engine in a Hough loader. This is a gravity fuel feed to the carb. Your Bobcat skidloader uses a fuel pump with the gas tank below the carb. This application is completely different.

    IHC liked to mount the fuel tank bottom at least as high as the top of the engine block. Air intake was above the hood making it above the fuel tank.

    intake and exhaust manifold bolted together close to where the carb was mounted on the bottom of the assembly for carb heat which did not work so great. They tended to ice up badly on humid days.

    The exhaust manifold was located above the intake runners so there was no where for the gas to go in an extreme flooded condition.

    The carb is likely a Marvel Schebler that was very common in these application and they always had a sintered bronze drain from the factory.

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  5. #24
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    Quote Originally Posted by Ziggy2 View Post
    We are talking specifically about an IHC gas engine in a Hough loader. This is a gravity fuel feed to the carb. Your Bobcat skidloader uses a fuel pump with the gas tank below the carb. This application is completely different.

    IHC liked to mount the fuel tank bottom at least as high as the top of the engine block. Air intake was above the hood making it above the fuel tank.
    Ziggy2 - you seem very familiar with these. Thanks for sharing your knowledge.

    The machine came to me with a little nub of brass fuel line connected to the carb. And a rag stuffed into the block on the opposite side of the engine. Where a fuel pump would go. And a brand new fuel pump in a musty cardboard box. I surmised that a fuel pump was part of the plan and bolted it on and was planning on plumbing it in. Any problem with this?

    Fuel tank is at the front of the machine and bottom of the tank is probably pretty close to the same level as the carb inlet. Going downhill it would definitely be below the carb inlet.

    Wandering a bit: Any recommendations for reconditioning the fuel tank? It has been sitting dry for 15+ years and appears to have some rust flakes and junk in it. I would like to clean it out and leak test it before putting it back into service. I'm not a huge fan of gasoline powered equipment ... so keeping gas leaks off my boots and out of the cab would be nice.

    Thanks,

    -Jim

  6. #25
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    Quote Originally Posted by Ziggy2 View Post
    We are talking specifically about an IHC gas engine in a Hough loader. This is a gravity fuel feed to the carb. Your Bobcat skidloader uses a fuel pump with the gas tank below the carb. This application is completely different.

    IHC liked to mount the fuel tank bottom at least as high as the top of the engine block. Air intake was above the hood making it above the fuel tank.

    intake and exhaust manifold bolted together close to where the carb was mounted on the bottom of the assembly for carb heat which did not work so great. They tended to ice up badly on humid days.

    The exhaust manifold was located above the intake runners so there was no where for the gas to go in an extreme flooded condition.

    The carb is likely a Marvel Schebler that was very common in these application and they always had a sintered bronze drain from the factory.
    1. You don't know my bopbcat so don't tell me what you think it is.
    2. Still how can the float chamber, overflowing because of a stuck needle and a gravity tank (common occurrence, and happens to be identical on a j-3 cub FWIW), put raw (liquid) fuel into the venturi, and then force it UP into
    the cylinders, whilst the air intake is not plugged tite ?

    It's gonna roll out the air intake.

  7. #26
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    A side note. After my IH 706 stuck the tousandth time I took it appart and bent the tabs on the float hinge so the needle can only drop about 3/16". The needle valve hasn't stuck since. I was concerned about getting enough fuel but its fine.
    Mine usually stuck on start up after sitting for a time and I suppose fuel level dropped in the bowl.
    Needle valve jams if float drops to far. It gets cocked at a slight angle. Its easy to suspect dirty fuel and sometimes is.
    The valve sticks not the float

    The hole in the bottom is to drain excess fuel. as so many others have said.

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  9. #27
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    Quote Originally Posted by mllud22 View Post
    A side note. After my IH 706 stuck the tousandth time I took it appart and bent the tabs on the float hinge so the needle can only drop about 3/16". The float hasnt stuck since. I was concerned about getting enough fuel but its fine.
    Mine usually stuck on start up after setting for a time and I suppose fuel level dropped in the bowl.
    Needle valve jams if float drops to far. It gets cocked at a slight angle. Its easy to suspect dirty fuel and sometimes is.

    The hole in the bottom is to drain excess fuel. as so many others have said.
    I recall my dad had an old Ford truck with a glass float bowl.

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  11. #28
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    Quote Originally Posted by digger doug View Post
    1. You don't know my bopbcat so don't tell me what you think it is.
    2. Still how can the float chamber, overflowing because of a stuck needle and a gravity tank (common occurrence, and happens to be identical on a j-3 cub FWIW), put raw (liquid) fuel into the venturi, and then force it UP into
    the cylinders, whilst the air intake is not plugged tite ?

    It's gonna roll out the air intake.
    Like I said, you are right about most.

    Some, including a little Briggs I have, have the inlet turn upward again, so the inlet is above the carb, and it COULD fill up. Maybe. Or suck in a cylinder load from the filled up manifold, and then hydrolock before it can drain out through the rings.

    Cases I saw just filled the crankcase through the ring gaps, but a bigger tank might let the cylinder fill. More likely to just fill the manifold and then suck it in.

    I'd not be so worried about hydrolock, more about where all that damn gas went, In the engine or, more interestingly, where it went when it finally overflowed, or drained out through the drain hole overnight........ Being as I might flip the light switch in the morning.... Better store that pup outside.

  12. #29
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    Nobody was stingier than Henry Ford, but every ford tractor I ever saw had a sintered plug in the bottom of his updraft carbs.

    JH


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