8N ford manifold swap

John L Mathis · May 21, 2017

Dad's 8n was in need of a new manifold. Exhaust ports rusted out and leaking. Purchased a new manifold at the local dealership. Tractor ran fine prior to swap with the exception of the exhaust leaks. After the new manifold was installed the tractor won't run when idled down and has a noticeable flutter out the exhaust pipe. All cylinders checked for spark.... good. I did however notice the port sizes on the new manifold were much smaller. Did dad buy the wrong one maybe?? Part number was 9n9425

JMOR · May 21, 2017

(quoted from post at 17:59:18 05/21/17) Dad's 8n was in need of a new manifold. Exhaust ports rusted out and leaking. Purchased a new manifold at the local dealership. Tractor ran fine prior to swap with the exception of the exhaust leaks. After the new manifold was installed the tractor won't run when idled down and has a noticeable flutter out the exhaust pipe. All cylinders checked for spark.... good. I did however notice the port sizes on the new manifold were much smaller. Did dad buy the wrong one maybe?? Part number was 9n9425

Port size difference won't do that.. I would look for leak. Un-lit propane applied around the manifold to engine interface and carb to manifold & listen to engine speed difference.

Bruce (VA) · May 21, 2017

If the manifold was rusted, chances are the
block was as well. Usually around # 4. Did
you check?
75 Tips

John L Mathis · May 21, 2017

the block was fine. Cleaned off the old gasket and the casting was very smooth.

Roger in Iowa · May 21, 2017

I had a new manifold that had an internal casting flaw with a passage between the exhaust and intake. Can check by
turning manifold upside down, put your hands over the intake ports to seal them, and pour water in where the carb
mounts. If water comes out the exhaust you have a faulty manifold.

ZANE · May 21, 2017

I had the same experiance with a Genuine Ford manifold back in the early sixties and it nearly drove me crazy before I figured it out. Big leak between intake and ext.

Zane

John L Mathis · May 21, 2017

I'll be sure to check that! The unlit propane idea is also a good thought to check for gasket leaks. The intake was stamped China..... Henry would roll over in his grave of he saw that!

Hobo,NC · May 21, 2017

I an gunna tell you how to eliminat a possible problem with the new manifold but first you have to send me $100 dollars...

Being the nice guy I am and to prove how smart I am I will for-go the $100

The exhaust stroke is no different than the intake stroke other than it pushes the compression event out the exhaust. If you were to shadtree a compression test you would remove a spark plug and hold a finger over the spark plug hole to see if it would blow your finger off the spark plug hole.

Take all the plugs out but one #1 cylinder remove the exhaust lead off pipe and hold your hand over the exhaust outlet spin the engine over it should try and pop your hand off the outlet. If good remove #1 spark plug and install a plug in #2 replete the process go to #3 then #4... If theirs a problem with the manifold you will not feel are get the same effect... remove the manifold and find were the problem is on that cylinder port that feeds that part of the manifold...

Roger in Iowa · May 21, 2017

All the exhaust ports in the manifold empty into a common discharge, therefore just checking one cylinder is enough,
except if you have a burnt or leaking exhaust valve in any cylinder. This is for checking for a bad manifold.

John L Mathis · May 21, 2017

i should be back home Tuesday to diagnose this. I'll post what i find. Thanks for all the input!

Tim PloughNman Daley RIP · May 22, 2017

The correct FORD N-SERIES exhaust manifold part number is 9N-9425, and it does matter where you buy from. Most all are foreign made now but some places like Cheena don't have quality control and use inferior materials. Did you put new paper gaskets on, two required? Did you use the right manifold studs WITH 7/16 Brass Nuts torqued to 27 ft/lbs? Is the clamp on the correct way? As stated, #4 port gets hotter because it right by the downward outlet to muffler, and thus the area will get worn first.

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9N 9425 Manifold

John L Mathis · Jun 3, 2017

Dad got back from vacation, took the manifold off and it was bad! Water ran right from the exhaust port out the intake. New part on the way. Thanks for all your help!!

8N ford manifold swap

John L Mathis

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JMOR

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Bruce (VA)

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John L Mathis

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Roger in Iowa

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ZANE

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Hobo,NC

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