M exhaust manifold

[Ellis Kinney]

I am probably going to need to replace my exhaust manifold this winter. I have welded the pipe back in twice with nickel rod and the cast manifold breaks loose from the nickel just below the weld. I am thinking really old brittle cast. Anyhow--- I have never replaced an exhaust manifold before and am really scared of snapping a stud off in the process. Should I warm it up and melt candle wax around the studs?? What is the best gasket?? I always read the pros and cons of using gasket sealer and which side to use it on. Also torqueing information. The engine and head were rebuilt in 2008 so it has been apart not too long ago. All advice and information will be appreciated. Thank you, Ellis

 

[DeltaSteve]

Ellis,did you preheat the manifold first? Get the manifold hot first. Running/workingthe tractor accomplishes this. Weld it while still hot.Then run the tractor a few minutes after welding.You need clean metal to braze or weld to. Take your small grinder and grind the top of manifold down to clean steel.Also clean the inside threads.A die grinder with a carbide burr is what I use. Then get a new piece of pipe. Grind one end to a taper. Enough to fit down into the manifold 1/2 to 3/4. You can braze it instead..Useing a large brazeing/welding tip,preheat the area to (almost) cheery red.Heat the pipe too.Then lay in brass around the pipe/manifold/ Be generous.After brazed,just let cool. Running the tractor for a few minutes wont hurt. You can do it right on the tractor. Done several.My good SuperM;400;F20;wifes SuperC;the neighbor girls A..... Havent had one fail yet.No need to buy a new one.

 

[Ellis Kinney]

I have done all of the prep you suggested. Very carefully. Only difference is that I used nickel. Thanks, Ellis

 

[BarnyardEngineering]

If it was apart that recently I would not worry too much about snapping off any head studs. Cheap insurance would be to heat the nuts. The studs don't need to come out. Usually the last time the manifold was off of one of these tractors was some time in the 1960's. 13-14 years is as good as yesterday especially if the tractor was kept inside.

 

[Bob M]

I've replaced several manifolds on H/M tractors with no issues. Generally the stud nuts turn off after a bit of heating. And the few nuts that would not loosen, the studs turned out easily from the head.

Incidentally my 'Minnie Mo has oversized brass nuts holding the manifold in place. All turned off easily after nearly 70 years in service.

For the replacements manifolds I installed the gaskets with no sealant - had no leaks whatsoever. However if the gasket surfaces are pitted, a light coat of high temp silicone around the center (intake) ports is suggested to prevent vacuum leaks.

 

[Fred47M]

Blue ribbon manual says 50ft.-lb. The caseih gaskets are very nice but double the price of the cheaper ones. I'd get the case ones again if I needed too.

 

[rustred]

The thing to use on exhaust gaskets is muffler cement. What is this talk of using silicone ?! Use the proper stuff gor the job. That is if the surfaces are not quite mating good due to warp age. If they are a good fit u use nothing. Tighten yo spec. Run and retighten. Standard procedure.

 

[Dieseltech]

Use a SHARP chisel on the nut flats about 1/8 inch deep on one or two flats, that will expand the nuts enough to get them off without breaking any studs. Easier to replace the nuts than deal with broken studs..

 

[kossuth]

(quoted from post at 17:16:41 07/08/21) The thing to use on exhaust gaskets is muffler cement. What is this talk of using silicone ?! Use the proper stuff gor the job. That is if the surfaces are not quite mating good due to warp age. If they are a good fit u use nothing. Tighten yo spec. Run and retighten. Standard procedure.

guess you havent seen the copper RTV thats out there for exhaust manifolds. https://www.permatex.com/products/gasketing/permatex-ultra-copper-maximum-temperature-rtv-silicone-gasket-maker/

 

[gene bender]

Clean the threads with a tap and screw a new pipe in

 

[rustred]

well if your going to just glue the gaskets on then yes use that . but on a tractor where you dont have a good seal and warpage it wont
work... u need muffler cement. dont believe all those crazy adds.

 

[gab]

If there's any sign of threads left shove a rag in the hole and run a tap in it. Then vacuum the chips out and screw a pipe in it.

 

[tractorguy2]

Ive never had a stud on a Farmall break off yet. I would be very, very surprised if the studs give you any trouble. I have never had any luck trying to thread a pipe into a manifold with burned out threads and make it stay after it has came out. I think you will need a new manifold.

Here is a quick true story about Farmall M's.

Back in the 80's My dad had a customer at his shop named Leroy that used Farmall M engines for irrigation. Leroy bought every Farmall M that came up for sale for parts or for the engines. Dad would remove the engine and put it on a stand and convert the engine to burn Natural gas. The New engines wouldn't run long before the Natural gas had the valve seats ate out. Dad always had a spare head ready to go and a magneto. The engines didn't have a charging system or a battery.

Leroy went through a lot of engines. Mostly from lack of oil changes and the hard water that clogged up the cooling system and caused a lot of cracked heads. Once we went out to Leroys farm to get the head off of one of his parts tractors. It was sitting down in the creek bottom along with a McCormick WD-9, two F-20's and part of a 22-36. The M was a 1943 war time tractor with nice cut offs on the rear and wide front axle. I hated to part that one out.

Dad and I removed the hood and I prepared to remove the manifold. I got out dads brand new 1/2 drive deep socket set. I placed the socket on the very first manifold stud and the socket split completely in half! Had to been a factory defect socket. We had to drive six miles back to town to get another socket. All the manifold nuts came off with no problem.

Later, Leroy cracked the block on another engine so the 43 M was pulled to dad's shop and we removed the block. I hated to cut that tractor up. I took a photo or two of it. Leroy destroyed several nice old Farmall M tractors. He had four Farmall M engines total. All running on Natural Gas. Kept dad busy all summer with just Leroy's engines. I still have the spare rebuilt head for Leroys engines and one magneto.

 

[teddy52food]

You can also try 7018 low hydrogen on old casting.

 

[300guy]

When I was a young kid working for an IH dealer, our shop foreman had a manifold with bad threads in it. So he decided to buy a brand new tap to clean the threads up and put in a new pipe. I remember all of us gathering around him so excited to see if this worked because we were always welding and adding a brace piece to the side of the pipe. Anyway he started running the tap down into the manifold and it sounded kinda like popcorn as the teeth popped off the tap. The threads were filled with carbon that was so hard it was breaking the teeth on the tap. So all I can say is we threw the tap in the junk pile and he welded a new pipe back into the manifold. The cost of a tap today that size is way too much to end up ruining it immediately after buying it. We sometimes took the new pipe and ground a V slot vertically up the threads and used that to help clean the threads a little as we tightened the pipe into the manifold. Most times after that we tack welded the pipe to the manifold to keep it from coming out.

 

[Fritz Maurer]

You are correct if they had cleaned out that hole shiny bright with a die grinder , it would have worked. What concerns me is the amount of torque it would take to cut the threads. Would those thin, aged manifold runners hold up to it?

 

[rustred]

definitly. just go slow and keep removing the tap to clean it. usually 1/4 turn at a time. i have tapped quite a few. it takes time about 2 hrs. you cannot rush it or you will be breaking threads off the tap. plus it takes a 36 pipe wrench on that tap.!