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Farmall C exhaust stem removal


Jesse in WI

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I am working on a Farmall C and trying to remove the stem that connects the exhaust manifold and the muffler. Previous owner put a pipe nipple in there and it's too short to put the muffler clamp on with the hood in place. I've soaked it in oil for two weeks with no results. Can I heat the cast manifold red hot and try to turn it out? Don't want to ruin the manifold. Or am I going to have to cut and chisel the pipe nipple away from the threads?

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I would cut it off flush and then make some slots on the inside of the nipple till it touches the threads so when you go in with chisel it’ll roll in and rip at the cuts 

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7 hours ago, Wi Ih said:

I would cut it off flush and then make some slots on the inside of the nipple till it touches the threads so when you go in with chisel it’ll roll in and rip at the cuts 

Yep, this works, done it twice - use hacksaw blade clamped in pair of Visegrips. A little slow and try not to get too far into the manifold threads.

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7 hours ago, Wi Ih said:

I would cut it off flush and then make some slots on the inside of the nipple till it touches the threads so when you go in with chisel it’ll roll in and rip at the cuts 

That was going to be my next course of action. 

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Those are basically a pipe nipple.

Rather than pay a super high price at the dealer, buy a piece longer than you need at a cheaper store.

Then cut it down to the proper length.

If you have a pipe thread tap, clean out the threads of the cast manifold and then screw in the pipe dry.

You will probably have to retighten the pipe a few times before it rusts into the manifold and stays tight.

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Running a pipe tap into rusty cast iron manifolds is a good way to ruin a good tap. Moly-disulfide grease on the threads of the new pipe and manifold. Use same chain wrench and cheater that removed it to install with similar torque. Will not have to retorque. 30+ years doing this way. Never broke a manifold. Only one would not hold. Hole was so large. Pipe bottomed on manifold curve and tipped pipe. Otherwise have screwed some pipes in 2 turns after threads disappeared and they held

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If you have a torch , just point it down into the pipe and blow a slot across the threads. You can’t cut the threads in the manifold unless you get them red hot. You have to be fast; don’t be timid and wait for the manifold to heat up, that’s where you get into trouble. Practice burning the nuts off a few 3/8” bolts; you’ll see the secret is keeping the bolt as cool as possible. Same with the manifold. If you chicken out on the first try, don’t try it again until you pack some wet rags around the outlet and get it nice and cool.

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I have a few ways to do this but this one is the safest to ensure theres no damage. once you get the pipe out if the threads are looking filled with rust take the manifold off and sandblast the threads, you be amazed how good the threads will clean up, its important to get them clean a little farther than the ones the old pipe took up, with the tapered thread it needs to go down until its tight not until it bottoms out in whats there

the Felpro number for the gasket is MS 8797 S to avoid the stealership's ridiculous pricing on the gasket set

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  • 2 weeks later...

Good news: we were able to get the pipe nipple out of the manifold using a pipe wrench and a 4 foot pipe

Not so good news: there are short pieces of old threads stuck in the cast manifold that I can't get out and are stopping the new pipe from threading in a reasonable distance.

Can anyone tell me what size NPT tap I would need to clean the threads out? Looks like 1-1/2" but I'm not certain.

I am trying to find a cheap tap for this one time use (hopefully). Is a plumbing supply house going to be the only place to find a tap this large?

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Use a small chisel to get the pieces out of the threads.

A tap should only be used to clean out the threads before you screw in the new piece of pipe.

It appears that 1 1/2" NPT is the correct size.

There are no cheap taps, or dies.

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12 minutes ago, Diesel Doctor said:

Use a small chisel to get the pieces out of the threads.

A tap should only be used to clean out the threads before you screw in the new piece of pipe.

It appears that 1 1/2" NPT is the correct size.

There are no cheap taps, or dies.

I started trying to use a small chisel but can't figure out how to get a good angle on it. I started to distort the good threads trying to work out the old pipe thread so I quit before I ruined the manifold.

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A number of years ago I paid a lot of money for the correct tap for the large size IH manifolds, after all I thought I would be doing this for years and need to do it often.  Like mentioned that cast iron manifold has been almost red hot for years in the presence of a lot of carbon.  A tap will not touch it.  There are a lot of good suggestion here but I can tell you from experience that a tap will not help you.  

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On 9/8/2023 at 4:43 PM, HydroTek said:

you want a small diameter punch -- grind a bevel on the tip -- use that to work behind the broken pieces -- there will be some thread damage , but it will only be a small place

This was the inspiration I needed. 

I used a nail set with a good sharp point on it and was able to work out the pieces a little at a time.

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