Carburetor Inlet thread size ?

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johnr
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Carburetor Inlet thread size ?

Post by johnr » Fri Mar 28, 2025 8:36 am

Is the inlet thread on a Holley NH carburetor 1/8 NPT ?
Tried running a new brass fitting and it would not start.
Chased the threads with a die with no help.
Threads in carburetor visually appear to be in good shape.
Curious before I pull the carburetor off an run a tap in which is
going to result in pulling apart and cleaning out possible chips and trash.

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DanTreace
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Re: Carburetor Inlet thread size ?

Post by DanTreace » Fri Mar 28, 2025 8:57 am

Yes, 1/8 NPT on inlet elbow. Tapping with carb mounted on intake provides poor working spaces, so care in going in straight. Use of vacuum could help remove minor iron chips in tapping. IMO, remove the carb and do bench work.

Cross section with thread sizes.jpg
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Harley_97
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Re: Carburetor Inlet thread size ?

Post by Harley_97 » Fri Mar 28, 2025 9:33 am

Also, if you have the 1/8 NPT die, use it to check the threads on the elbow.

Roger


speedytinc
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Re: Carburetor Inlet thread size ?

Post by speedytinc » Fri Mar 28, 2025 10:38 am

Your new fitting is suspect. Dont ruin a carb body modifying it to fit the bad fitting that needs a correct thread cutting.


Topic author
johnr
Posts: 57
Joined: Wed Mar 16, 2022 2:09 pm
First Name: John
Last Name: Delamater
* REQUIRED* Type and Year of Model Ts owned: 1927 Depot Hack
Location: Huron, Ohio

Re: Carburetor Inlet thread size ?

Post by johnr » Fri Mar 28, 2025 12:27 pm

thank you all.
Pulled the carburetor an found a burr on the face of the thread inlet.
Ran a tap in and cleaned up the threads.
Fitting went in perfectly.

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