Exhaust manifold exhaust pipe threads

[8NHENRY]

So my old 44 at some point in its life the exhaust pipe must've came loose in the manifold and buggered up the threads. I am thinking about chasing the threads and trying a new pipe in it. Looking for anyone who has done this before and any advice.
Thankyou

 

[Big Fat Herb]

I have used pipe taps bu the old manifolds are hard . Ive had better luck with a dremel with a cut off blade.

 

[Oregon Tractor Jack]

I have done several of them. The old pipe really gets cooked in to the manifold and it is really hard to chase the threads. The other problem is finding a tap. They are VERY expensive. I got lucky and found someone that had one for me to borrow. It might be cheaper to buy an after market manifold or find a good used one. The other alternative is to weld a pipe nipple into the manifold.

OTJ

 

[wore out]

''Taps are VERY expensive.''


Sometimes you can find good used quality American-made pipe taps on ebay quite reasonably.

 

[gene bender]

thats what i do it takes time to get the threads clean again with the buildup junk in the threads but sure worth your time then
NEW pipe

 

[timcasbolt]

(quoted from post at 07:56:53 09/17/23) So my old 44 at some point in its life the exhaust pipe must've came loose in the manifold and buggered up the threads. I am thinking about chasing the threads and trying a new pipe in it. Looking for anyone who has done this before and any advice.
Thankyou

did a Farmall H once. Think it was 2". Got lucky. A friend had connections with a plumbing contractor and was able to borrow one for a day. That 50 year old iron sure was crispy. Crisco helps.

 

[Moonlite37]

Rough on the tap. I bet thee flows did not tell the owner what they were going to do

 

[r.w.b.]

massy harris 44 n 444 seems like taps hit casting below threads before tap is
actually cutting rust n junk. i cut a pipes threads off about 2 threads n cut slots
in it ,ran it in n out few times then got another pipe ,cut first 2 or 3 threads off.
put pipe in deep freeze n let it chill all mornin. afternoon got a friend to hold
heat gun to manifold n get it hot at thread area. screwed cold pipe in n pulled it
tight with a 3 ft pipe wrench. it was oh 3 years later when i traded it off

 

[farmallboy15]

Did that this spring on my 706. Used the cheapest 2 npt
tap I could find on Amazon. Worked just fine.

 

[8NHENRY]

Thankyou for the reply's will be working on that this winter.

 

[Russ from MN]

I repaired the threads on my father's IH M, I believe it was a 2-inch tap, I was able to borrow one from my place of work. I put an oily rag down in the manifold
to catch debris. As I remember I had to use a pry to get enough force to start the tap, but I got it done, and screwed in a new pipe nipple.

 

[dhermesc]

I borrowed a tap from a plumbing shop and chased the threads on my Farmall 350 exhaust manifold. I then got a new pipe and cut new threads on it. I hoped the new threads on the pipe would help make up
for the smoothed-out threads on the manifold (not enough metal left for sharp like new threads). It held for a couple years then it came loose again and I bought a new exhaust manifold.

 

[Ellis Kinney]

If you can weld well I would use nickel 99 instead of the re threading process. I have chased the thread before with limited success. Outside the box-- I
bought a 2 inch pipe fitting and cut the threads off one end and machined it smooth. Drilled 8 holes through it and drilled and tapped 1/4-20 into the manifold
and bolted it on using cap screws and a copper gasket. This lasted about 30 years until I rebuilt the engine. Ellis

 

[8NHENRY]

Thankyou all, allot of good information here. I do have access to a tap so I will try that first. Ellis when you drilled and tapped the 1/4-20 bolt holes did you drill and tap the manifold or all the way into the pipe as well? I do not have a welder so that would be an option for me to try if the tap fails to work. The tractor will see less than 50 hrs a year, mostly tractor rides and maybe plowing once year so no real hard use.

Thanks once again