Manifold question

Why do the manifolds on the N Tractors seem to crack? I put one on the '52 sidemount years ago when I first got the tractor, it had a cracked and leaking manifold. Fast forward about 15 years and it has been leaking recently. I thought it was the old exhaust pipe (been knocked off several times and muffler was shot) that would not seal up anymore. I got a new one piece exhaust and sealed it up and ....still the manifold leaks. About that time I realized it wasn't the exhaust pipe that had been leaking but the dang manifold behind there. Guess I need to order a new one. Just wondering why these things crack over time?

how pitted is the block? Are you putting any sealant between the block and manifold if the block is pitted? A smooth block and new manifold should not leak. Why they crack I dunno someone else can chime in.

Metal fatigue, is the main reason they crack. Hot to cold hot to cold. Expand and contract, expand and contract. In the aircraft industry metal fatigue is its worst enemy next to gravity. When an aircraft is pressurized the fuselage expands (as heat is to manifold). When the pressurization is released it contracts (as cooling is to the manifold). Every time this happens it is a called a cycle and after so many the aircraft must be inspected for metal fatigue. Unlike the manifold when it gives up no big deal cause you are on the ground and ya can park where your at, but on an aircraft it could be a long drop to a parking space.Sorry about the hair cut deal,think pig tails. Master of the obvious LB

#4 cyl.started leaking on the 9 used a steel reinforced epoxy putty as temp repair..been there for about 20 yrs. still holding..easy to apply..press into gap around manifold..phil

if the ep has been knocked off several times.. that means the manifold has been stressed multiple times.

and the new ones ain't as good as the old ones...

Thanks everyone. That makes sense about the hot/cold cycles. This was a brand new manifold 15 years ago, so it lasted a good long while and a lot of bush hogging over the years. I might try the epoxy fix. I am planning on rebuilding the engine some time this winter/spring and I would replace it then anyway. Thanks again.

No pig tails! Thanks for the info, Im always eager to learn about this sort of stuff! Maybe in 20 years when im 50 i'll know a bit more!

cast iron seems tough, but it ain't.
I've broke enough of it freeing up rusted parts
with whacks that wouldn't have hurt a tin can.
Like SG says, sometimes it only takes one muffler hit
to do it.
That muffler-pipe is a very long lever....

Stang-
I have never seen nor have had a Ford N-Tractor exhaust manifold crack. They will however, blow out right at #4 cylinder port -where the pipe connects, nearest the operator. That area gets the hottest and will burn out the gasket there then start to wear a channel in the cast iron metal itself. If left too long it will start to wear into the block and you don't want that. It's a lot cheaper to replace a manifold than a block. The other issue is that the exhaust manifold uses brass hex nuts to fasten it to the block with and sold in kits -try nnalert. They get torqued to 27 ft-lbs. Assemble new manifold with two new gaskets -no sealant required - and torque to specs. After running engine until hot for a good 1/2-1 hour, shut down, let cool down then re-torque. Studs are made with one end having a coarse thread -this end screws into the cast iron block, and the other end having a fine thread -this end accepts the brass nut using a steel lockwasher. If you are using steel nuts, you may be cracking the block that way with too much torque, and as mentioned, whacking off the pipe numerous times will only cause stress on the manifold. I can't comment on the new manifolds -last one I bought was made in India and has been OK. I'd have to perform a Brinnell Hardness Test on the actual metal to determine it's effectiveness. Cheena made items have a poor reputation no matter what the product is. Many manifold kits I have looked at have the new manifold, and the three gaskets -two for the exhaust ports, and one for the carb. Be sure to scrape off all the old gasket material from the block before assembling. Also, soak the carb gasket in gas prior to final assembly. I'd try to buy a new one that was made in India or Brazil for a better quality.

Tim 'PloughNman' Daley(MI)

"They will however, blow out right at #4 cylinder port -where the pipe connects, nearest the operator."


Ahhhh, that is exactly where it is leaking thus making me think it was the pipe hook up originally. Good info int your post. Thanks.

(quoted from post at 07:19:40 09/29/13) Assemble new manifold with two new gaskets -no sealant required - and torque to specs.

Click to expand...

Tim, good advice here!
When I first read this statement about two new gaskets, I thought
you meant to put in two sets. Two thick, doubling them up.
After re-reading, I think you meant the two that come in a kit,
one for each half of the manifold.
I thought I would ask just in case anyone else read it like I did.
One thickness is plenty. No sealant needed with good surfaces.