John McEwan

Exhaust manifold thread size

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Does anyone know the size/pitch of the large thread at the exit of the exhaust manifold of a 1923 Dodge?

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John what are you trying to do please explain thanks.  Mike

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The one at the arrow? Should be two of them?

image.png.41b5bc96d71a5d2ed77a85574ef310b5.png

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Spinney....I think he means the large exhaust pipe collar threads like on the rear of this manifold....

DB engine.jpg

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Yes, mine has the large single nut. The nut I have seems ok but the threads on the manifold look worn down. The nut slips on half way up the thread before it grabs. I thought I might take it to a machine shop and have them build up that area with braze then recut the thread.

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The nut has not came loose. It is I cannot use a ring gasket between the manifold and the first pipe because the nut doesn't grab the manifold at the start.

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John I had a similar problem I got a peanut and packing from Myers and used valve grinding compound and worked the nut by hand until it would screw on up the the shoulder on the manifold wrapped the packing around the pipe run the nut up to the shoulder and that keeps the pipedream free I think it cost less than $25.00     Mike

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Find your self a thread file, McMAster-Carr sells them. They have 8 different pitches  and there is two different ones to cover almost any pitch you need. You can dress the threads with that. Decide what pitch thread you have and use the file like a real file, in ONE direction. Work your way around the diameter. 

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For the record the thread is a nominal 2 3/8" x 16tpi. The spare I have measures 10 thou under this for an easy fit.  The easiest way out if your threads are worn is to have an oversize nut made up. 

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Hi just reading my post.  New   nut.    Not peanut.    Leak. Free. Not pipedream. Just love this spell check.  Mike

  • Haha 2

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I was just reading your previous post and thought what the hell is he talking about, lol

All good suggestion. Thanks everyone.

  • Haha 2

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14 hours ago, Mikefit said:

John I had a similar problem I got a peanut and packing from Myers and used valve grinding compound and worked the nut by hand until it would screw on up the the shoulder on the manifold wrapped the packing around the pipe run the nut up to the shoulder and that keeps the pipedream free I think it cost less than $25.00     Mike

Is the packing used on the manifold thread like a thread tape and is it like a ribbon or rope?

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Posted (edited)

Like rope or similar to water pump packing some one it's the same thing they use on wood stoves doors     the packing goes on the pipe at the shoulder where it slides into the manifold    Mike

Edited by Mikefit
Adding instructions (see edit history)

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Bought a new nut and worked it onto the manifold thread with valve grinding paste as suggested. New header pipe, packing and copper crush rings and it’s nice and quite. Sure makes a good difference.

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