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Farmall & IHC Tractors Discussion Forum
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Carburetor Packing Nut, what purpose does it serve

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aaron

12-15-2003 10:00:17




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Hello,
I just rebuilt a Farmall H carburetor and put in a new packing nut. Had to use a drill bit to remove the old one. I noticed that the old one was about 3/4" long, extending all the way up to the drain plug outlet. The new one was only a 1/4" long. I am clueless as to the purpose of the packing nut. I spent a long time meticuously cleaning and doing a complete rebuild on the carb, and the last thing I did was remove the old packing nut and install a much smaller one and I feel that I should have left the original longer one in there. Just frustrated that it may be worse off now than before. Comments?
Thanks,
Aaron

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rebuilder

12-15-2003 12:00:32




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 Re: Carburetor Packing Nut, what purpose does it s in reply to aaron, 12-15-2003 10:00:17  
Aaron: I want to make sure we are talking about the same thing. The packing nut is brass and is about 1/4" long as you described. These fit all I.H. carbs from H up through 856(c-310). There is only one size and unless things have changed recently, they are not made anymore by I.H. When you say you had to drill out the nut were you talking about the nut or the packing. The packing also is 1/4" long approx. If you did have a 3/4" packing nut then the carb. has been modified at some point in time. I see a lot of this usually in the aluminum carbs rather than the cast iron. Guys get to aggressive in tightening the threads and strip or cross-thread them. Or try to put in a pipe plug which has totally different threads. So My guess is someone botched your threads in the packing nut oriface and bored and tapped new threads to accomodate a packing nut from some other application. There is no good way that I know of to return your carb to original other than replaceing the bowl with one that has good threads. This may be harder than you think because the Farmall H carb. bowls had several weak points in them and many have been junked. I myself keep some bowls on hand but I don't sell them because I have a greater need for rebuilt carbs. The yard I work for prices rebuilt carbs around $195.00 exchange(this may be an old price as I don't associate myself with the day-to-day sales). Good luck and post if you have any more questions. P.S. I believe the external threads on the packing nut are 7/16-32? fine thread and 1/4-32? internal. I should have these threads memorized by now but double check.

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aaron

12-15-2003 17:45:53




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 Re: Re: Carburetor Packing Nut, what purpose does in reply to rebuilder, 12-15-2003 12:00:32  
Thanks for the info!
So, a fella should NOT overy tighten the nut when rebuilding the carb. Just snug. He should only tighten the nut after an adjustement has been made, which will press the packing material against the needle.
Makes sense now. I really appreciate your response, you have really helped me understand this point. Now I can be smart about such matters and not tighten the nut to the point of breaking the casting. Will thread tape be effective on the needle threads should the packing not press against it hard enough?
Thanks,
Aaron

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rebuilder

12-16-2003 03:54:15




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 Re: Re: Re: Carburetor Packing Nut, what purpose d in reply to aaron, 12-15-2003 17:45:53  
Aaron: You should not need any teflon tape on threads, the packing should be doing all the sealing. Especially if the packing is new and most pliable. As packing ages however, it hardens and may not seal as easily, but we are talking quite a few years. I tighten the brass packing nut on rebuilt carbs just so the needle turns somewhere between tight and snug. I don't want to be able to turn the needle with my fingers and a screwdriver should have resistance. Basically if it is tight turning you have the packing tight enough. I hope I did not over explain myself.

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thanks- aaron

12-16-2003 09:43:56




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 Re: Re: Re: Re: Carburetor Packing Nut, what purpo in reply to rebuilder, 12-16-2003 03:54:15  
No, You did not over-explain yourself. Details are good to know. There is alot of value in the details that you have given. Thanks again for all your valuable advice and knowledge.
-Aaron



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rebuilder

12-15-2003 12:04:40




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 Re: Re: Carburetor Packing Nut, what purpose does in reply to rebuilder, 12-15-2003 12:00:32  
Aaron: Sorry I forgot to tell you the packing is to seal the gas from leaking out around the main fuel adjusting needle which is what goes through the nut and the packing. This way you can turn the needle either way without losing you sealing capability. If it starts to leak just turn the packing nut a couple more turns to jam the packing tighter and created a new seal.



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Nebraska Cowman

12-15-2003 11:08:31




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 Re: Carburetor Packing Nut, what purpose does it s in reply to aaron, 12-15-2003 10:00:17  
i find lots of stuff that is not as good as the original; but it's too late now!



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