Farmall C exhaust manifold

kennell · Apr 13, 2010

My exhaust manifold isn't in very good shape thread wise. I borrowed a 11/2 tap from another tractor guy. Troble is i can't get the tap to atsrt into the threads. Anyone have any secrets as to getting the tap to screw into the manifold? Thanks Kent

Janicholson · Apr 13, 2010

Rust is very tough and hard. It is causing your issue. Wire brushing is not going to touch the rust. A cone shaped stone on a die grinder will. Just remove enough rust to see cast iron, do not hog it out.
It is necessary to realize that it is already rusted through the place where the threads should be. The result will be threads lower in the manifold. No problem if the pipe you use can be trimmed shorter in the threads to keep it bigger than full tapered threads. Cutting off a little (1/4 to 3/8 of the top of the manifold will make it closer to the proper size where the threads will go.
It is important to use a great thread cutting oil (Tap Magic is the best I have ever found). A system to firmly hold the centering hole of the square end of the tap directly over the center of the hole, and a means to put about 100 pounds of down force on it will help. As will using a real tap wrench with equal force applied to rotate the tap, (a crescent wrench pulls sideways as well as turns) Best of luck, Jim

Russ from MN · Apr 13, 2010

I re threaded my Fathers M many years ago, and I had the same problem. I took a good 8 foot 2X4 and drove a spike through with the pointed end sticking out enough to go in the center of the tap. This nail was about 2 ft from one end. Then we ran a chain around the short end of the 2X4 down to something solid, don't remember what, the M had a loader on it. then Dad pulled down on the other end to put significant pressure on the tap, I held it square and started it. after a few revolutions then the pry was not necessary any more, and I tapped the manifold deeper as Jim suggested. I had a piece of stainless pipe with lots of threads on it and used anti-seize to assemble it, worked good. Good luck!

gene bender · Apr 14, 2010

I have used a torch to get them hot then when its cool the stuff in the threadscan be removed then you can chase the threads.

rustyfarmall · Apr 14, 2010

(quoted from post at 03:47:24 04/14/10) I have used a torch to get them hot then when its cool the stuff in the threadscan be removed then you can chase the threads.

Yes, a torch will loosen that rust and allow you to get the tap started. Just be sure to let the manifold cool completely before tapping.

kennell · Apr 14, 2010

Thanks guys for the advice. I'll keep you informed about my progress. Kent

Farmall C exhaust manifold

kennell

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Janicholson

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Russ from MN

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gene bender

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rustyfarmall

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kennell

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