Tips for Replacing Manifold Gasket

whaNcock

Member
I have a 1950 8N, front-mount with serial number 257XXX. It seems it's time for me to replace the manifold as hot exhaust gas (and an occasional spark!) recently started escaping in the circled area in the picture between the block and manifold. There is quite a bit of back-firing until the engine is completely warmed-up, but after 10-15 minutes, it runs pretty smooth. I'm guessing the leak reduces as the block and manifold get hot and expand.

I would appreciate any tips or advice prior to me tackling this one. While simple on paper, I'm guessing there are other parts I should go ahead and replace during this repair outside of the manifold, manifold/block gasket, and muffler assembly (the muffler pipe at the manifold is almost rusted through as well). It's probably best to replace all associated nuts and bolts, but I'm wondering if the manifold stud bolts will come out or not. What do you suggest?

Thanks for the help!

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I just dealt with the same problem on my 9n. I cleaned both the manifold and block really well,then wiped them with acetone. I used some high heat epoxy by spreading it on the block,put some Saran wrap on it,then the manifold with some of the epoxy on it and tightened the nuts. After some judicious sanding on the manifold and using a Dremel on the epoxy that oozed out of it's intended area. It started with no leakage[yet!] Several people on this site have done writ-ups about this procedure,so not my idea.
 

I hope you haven't been driving it too long with that manifold leak. I surely wouldn't run it any more until it is repaired. The more you run it like that, the more chance it has to erode the block face.

You need to get a new manifold on it before that happens. I'm assuming from what you posted that your idea is to replace the manifold. That's what I did when mine started to leak in the same place. Manifolds are not that expensive.
 
If you get a new manifold be ready to grind the manifold or grind a 11/16" socket thin in order to get the end nuts tight. I got
two manifolds and both are the same oversize. Others on here said they had the same problem.
 
Thanks for the comments. I will be replacing the manifold. Fortunately, I haven't had this issue for long, so I'm hoping the block will still be in good shape. If not, I'll try Tip #53.<p>I'm still curious about the 4 stud bolts. I've read on the forum that I need to drain the radiator if I'm replacing the studs because they enter the water jacket. Is that so? Any other advice to avoid big mistakes?
 
(quoted from post at 16:16:51 08/21/20) Thanks for the comments. I will be replacing the manifold. Fortunately, I haven't had this issue for long, so I'm hoping the block will still be in good shape. If not, I'll try Tip #53.<p>I'm still curious about the 4 stud bolts. I've read on the forum that I need to drain the radiator if I'm replacing the studs because they enter the water jacket. Is that so? Any other advice to avoid big mistakes?

Why would you be replacing the studs? I pulled my old manifold off with no problems. I replaced it with the new manifold and new brass nuts from YT. I had no reason to replace the studs.
 
Why would you be replacing the studs? I pulled my old manifold off with no problems. I replaced it with the new manifold and new brass nuts from YT. I had no reason to replace the studs.[/quote]

I don't want to remove them, however, the nuts and studs are very rusted. So rusted that the nut and stud look like they've become one piece. I think the studs might come out when I start loosening the nuts, and even if they don't, the threads might not be in good enough shape to keep them in place or the studs might break. I don't want to replace the studs unless I have to, but I like to plan ahead to minimize issues.
 

i can get a socket on mine by feeding the socket up by hand from below, rather than in horizontally, and then put an extension into it to drive it. YMMV.
 
(quoted from post at 20:16:51 08/21/20) I've read on the forum that I need to drain the radiator if I'm replacing the studs because they enter the water jacket. Is that so?

yes. i can't remember if it's 2 of them or all 4.
 

Good chance you'll run into fitment problems with "Chinesium" aftermarket manifolds.

As mentioned some you can't get a socket/wrench on the mounting nuts. I got one I had to send back as it was mis-shapen and the throttle linkage would not clear it. I did get one years ago that fit perfect. Get the brass manifold nuts.

The epoxy fix for eroded block surface is a great idea.

If you have adjustable tappets, it's a good time to adjust them with the manifold off. Get the tools needed to adjust them.
 
The exhaust manifold wears/corrodes a channel at and around the #4 port (nearest dash) and that is where it leaks the most The exhaust manifold wears a channel from heat on the surface at #4 port as that gets the hottest and at the 90° downward pointing cast portion pipe that clamps the exhaust pipe/muffler assembly. Once worn it also destroys the gasket in that area. The 9N-9425 Manifold incorporates both the intake and the exhaust. Your intake flange has the carburetor mounted to it. I advise to replace the manifold with a new one and don’t think about trying to ‘band-aid fix’ with multiple gaskets and/or Permatex. The job isn’t difficult, just time consuming as you need to remove a few other components in the process. You don’t want to have to do the job twice so even if your band-aid works, it would be short term so do the job right the first time and replace again a few years later when it gets worn again. If your exhaust pipe is in bad shape, you may want to replace it too at this time. Parts can be purchased at reliable suppliers - see LINK. The manifold kit includes the three gaskets –two on the engine mounting surface and one on the carb mount. You will also need to get the four 7/16-20 BRASS hex nuts with steel lockwashers, p/n 33816-KIT, that are needed to fasten the manifold with. The carb needs to come off. The air cleaner tube and rubber hose also needs to come off. There is a rubber hose and two clamps on the top of tube as well. My technique for maneuvering the rubber hoses around is to spray some WD-40 up around the inside of them. Gently pry a screwdriver around lip to get it in. This makes the rubber hoses easy to work with. When removing/replacing an exhaust manifold, it is a good idea to drain some coolant first. Why? Often a 7/16 stud or two will come out as you remove the old hex nuts. OEM nuts are BRASS as stated. The bottom of the radiator has a petcock on the LH side for draining. When installing the new manifold, be sure to get all the old gasket material off the block first. New manifolds usually come with the three new gaskets but there's no need to put any Permatex on when reinstalling, I don't. Two gaskets go on the block between the manifold, one on each side, not double stacked. See your manuals for your guide. Brass Hex Nuts are torqued at 27 ft/lbs. Use a new muffler clamp as well. See Bruce’s method for installing a new pipe using a block of wood and a scissor jack. The muffler clamp has large side and a small side. The large side goes on the bottom. No need to use Permatex, tin foil, or heat tape here either. See ‘75 Tips for N-Owners’ by Bruce(VA). Get new manifold and muffler connected first then install the carb and air cleaner tube. No need to replace studs. Torque is set in three steps. By the way, all N' engine blocks are the same as far the manifold goes. Serial number doesn't mean anything. Get out your ESSENTIAL MANUALS and use for a guide.


FORD TRACTOR 39-50 ENGINE EXPLODED VIEW:
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FORD 8N TRACTOR ESSENTIAL OWNER/OPERATOR/PARTS/SERVICE MANUALS:
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Tim Daley(MI)
EXHAUST MANIFOLD BRASS NUT KIT
 

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