OT: Mystery hole in bottom of up-draft carb
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  1. #1
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    Default OT: Mystery hole in bottom of up-draft carb

    I have a new to me 1960'ish Hough H50 Payloader. It sat for 15 years and came to me with an inoperative carb. I've rebuilt the carb and have the engine running. But I am mystified by a hole at the bottom of the up-draft carb.

    The mystery hole is a nicely machined hole in a cast boss. Hole diameter is 0.162" and there is a nice 0.375" diameter counterbore. No threads. The face isn't machined. The hole is after the choke plate. So if left open, it would be sucking in outside non-filtered air. Or make a nice passageway for ants and bees and whatnot.

    Beyond the very poor carb kit instructions, I don't have any documentation on the carb. I don't see any lines running to it in the Payloader manuals.

    Any ideas?

    (boss / hole in question is centered in the palm of my hand in the first picture looking towards the choke plate. Near my pinkie in the second picture. And dead center in the third picture looking at the carb upside down on my bench)

    Thanks,

    -Jim

    scaled_image-2-.jpg

    scaled_image-1-.jpg

    scaled_image.jpg

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    Engine is an International Harvester inline 6 cylinder. I was able to google the number on the brass tag on the carb and get a (crummy) rebuild kit. That lists applications in various other vintage IH equipment.
    https://www.steinertractor.com/IHS32...tor-Repair-Kit

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    Fuel drain if the float sticks.

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    My plan, unless I get convinced not, is to plug the hole. JB Weld or a 3/8" wooden dowel both seem like they would be reasonably solid but removeable solutions.

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    Quote Originally Posted by gbent View Post
    Fuel drain if the float sticks.
    Hrmm. That makes sense. I have had raw gas pour out of there when I flooded it. Should there be a screen or something on there to keep insects and dirt out?

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    Overflow drain.. take that thing apart and clean, probably a brass on brass needle/seat. If it leaks lap it in with some fine lapping compound. The modern fuel is so corrosive it loves eating them up.

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    I would shove some brass wool in to keep junk out but allow liquid gas to drain. Or make a plug from sintered brass bearing stock that will allow gasoline to leak out.
    Bil lD

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    Quote Originally Posted by kb0thn View Post
    My plan, unless I get convinced not, is to plug the hole. JB Weld or a 3/8" wooden dowel both seem like they would be reasonably solid but removeable solutions.
    The hole is for a gas drain from excessive flooding. Originally there should have been a sintered bronze plug in the hole. Porous enough to let the gas leak out but small enough holes to prevent the creepy crawlers and dirty from getting in.

    I would not just put a plug in it as the air intake can become totally filled with gas if the float sticks which was also a frequent occurrence with updraft carb applications in that the gas tank was usually mounted above the carb elevation.

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    It is, as others have said, a float overflow drain. It is necessary and there is normally a pressed in hose nipple and a connected hose to allow the overflow fuel to exit the engine space to prevent fire. Nothing is necessary to block that hole. Make certain you install a nipple and hose.

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    Thanks guys! All makes sense now. Will machine a nipple and put a hose on...or a sintered porous plug.

    Thanks,

    -Jim

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    Quote Originally Posted by kb0thn View Post
    Thanks guys! All makes sense now. Will machine a nipple and put a hose on...or a sintered porous plug.

    Thanks,

    -Jim
    Sintered plug, yes. Fitting and hose,no, this filters air and stops crawly things HOW? It is a drain for sure. Does this thing have gravity fuel feed? If so and you plug it and have the float valve leak you will find your tank empty and your engine full.

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    Quote Originally Posted by moonlight machine View Post
    Sintered plug, yes. Fitting and hose,no, this filters air and stops crawly things HOW? It is a drain for sure. Does this thing have gravity fuel feed? If so and you plug it and have the float valve leak you will find your tank empty and your engine full.
    Simple solution. Put an inline filter in the hose. Steve-I is right that the proper way is to make sure the hose routs overflow past anything that could catch fire unless drained gas would already go straight to the ground.

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    I have a older Fordson tractor with a down draft carb. . The branches of the cast iron intake manifold below the carb each has a pressed in brass "Valve".
    The "valve" consists of a loose brass disc that serves as a self closing one way. Intake vacuum does the job of pulling the disc up and closed. When the engine is not running, the disc falls loosely in the fitting allowing any liquid fuel to drain away.

    During the starting sequence, especially when cranking on the starter handle, on occasion, the engine won't make it over center before the magneto sparks the plug. With a "CHUFF" the engine motors backwards, and excess fuel spews out from those two fittings in a terrible mist .

    Note, the entire fittings can't be much more than 3/8" in thickness, and are press fit in the holes in the manifold.

    The carb you have might be fitted similarly if you had one of the valves.

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    Also long bolt holds air cleaner on.

    Sent from my SAMSUNG-SM-G930A using Tapatalk

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    Quote Originally Posted by Scottl View Post
    Simple solution. Put an inline filter in the hose. Steve-I is right that the proper way is to make sure the hose routs overflow past anything that could catch fire unless drained gas would already go straight to the ground.
    Whatever blows your dress up, Just make sure it can drain. If it fills with fuel and someone trys to start it you may have enough fuel in there to hydraulic it with a good chance of a bent connecting rod.

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    Quote Originally Posted by moonlight machine View Post
    Whatever blows your dress up, Just make sure it can drain. If it fills with fuel and someone trys to start it you may have enough fuel in there to hydraulic it with a good chance of a bent connecting rod.
    What scenario would enable hydraulic lock ?

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    Quote Originally Posted by digger doug View Post
    What scenario would enable hydraulic lock ?
    I think John is thinking downdraft carb.

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    I've got an old 50's IH "300 Utility"... with that carburetor on it's 4 cylinder OHV engine.

    It's got something plugging that hole... nothing ever drains out of it~ I think it IS some of that sintered bronze.

    I've had the float stick and fill up the breather pipe... nothing drains out that hole. Just plug it with anything that won't fall out.

    Here a while back my carb was not letting the engine run right. A friend had an ultrasonic cleaner. I disassembled my carb and let it soak...

    Put it all back together and the engine purrs like a kitten. Outside of carb has a nice, rusty iron patina.

    The only thing I've ever had to do with this thing is put in a new brass float in the bowl. Somehow, it collapsed.. don't know if water got inside the bowl and froze, or what.

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    Quote Originally Posted by moonlight machine View Post
    Whatever blows your dress up, Just make sure it can drain. If it fills with fuel and someone trys to start it you may have enough fuel in there to hydraulic it with a good chance of a bent connecting rod.
    I give.
    Assume free flowing fuel pouring into the motor as it sits
    How does it hydraulic and bend a rod? The starter does not have this kind of power and since the intake is flooded I don't see how any of the others fire.
    I have hydrauliced more than one motor and bent/broken rods but always with water coming in while it was running.
    Won't it just not turn over more than a touch and stop? BTDT with "leaky" fuel or oil systems.
    Have you seen this destroyed rod happen? You do race motors I think from posts. Seen this lock and harm on anything standard?
    It is very bad and the gasoline bypasses the rings and fills the crankcase until it finds somewhere to vent which is a whole nother problem.
    I 100% agree that the drain need to be there and if it drips at all something is not right.
    Weird that thought of a screen to keep things other than dirt out. What kind of critter climbs in a tube filled with gasoline vapor? You must have some serious bugs.
    Bob

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    Quote Originally Posted by digger doug View Post
    What scenario would enable hydraulic lock ?
    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.


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