Mmmmmm donuts, a long winded rant and cry for help.

[IOPort51]

On the 1977 CJ5 with the AMC 258 i6 / 4.2l l6 the exhaust manifold to pipe is held by a lifting clamp and sealed by a bell on the pipe making contact with a donut gasket.
This gasket, I think this is the best name for it, is flanged into the manifold and has a composite 1/4 round ring fitting into the belled end of the pipe. Later models eliminated the gasket and made the 1/4 round a cast steel part of the manifold.
The gasket fails because the pipe has some movement to it under the best of conditions, which abrades the composite which gives more room for movement and on and on. I also suspect that if the gasket is hot, which it is most of the time and it gets wet, like driving through a puddle, that this also helps deteriorate the gasket. The second part of the problem is that access to the clamp bolts is restricted and the studs themselves seem to want to weld themselves to the nuts that take the weight of the pipe and make the whole thing a royal PITA.
I am, at this time resisting the installation of headers, just because I have not yet decided to opt out of the emissions test program and work outside the law, it kind of sounds like fun when I put it that way.
Have any of you with this arrangement, I don't know what years this will cover, found a workable alternative? Is there a "super gasket" I have been unable to find? I am about to have to spend some quality time with this issue and if there were to be some way that this could be the last time I did this it would be a good thing.

I am thinking about making a donut from steel which will be a pretty major project so if anyone has an alternative I would greatly apriceate it.

 

[W7NB]

You might want to look at the motor and Transfer Case mounts first. This is a common problem in a lot of vehicles. Yes, the gasket is failing, but often the problem is worn mounts allowing the motor to rotate under load farther than the exhaust joint was allowed to tolerate.

Also, check the alignment of the joint without the doughnut in place. If the rubber carriers in the exhaust are worn or the mounts are damaged the pipes may be far enough out of alignment that the gasket can't hope to make a good seal, and begins to leak.

 

[CJ]

Don't forget the liberal amount of graphite that should be applied on the metal to fiber conections.

 

[IOPort51]

You might want to look at the motor and Transfer Case mounts first. This is a common problem in a lot of vehicles. Yes, the gasket is failing, but often the problem is worn mounts allowing the motor to rotate under load farther than the exhaust joint was allowed to tolerate.

Also, check the alignment of the joint without the doughnut in place. If the rubber carriers in the exhaust are worn or the mounts are damaged the pipes may be far enough out of alignment that the gasket can't hope to make a good seal, and begins to leak.

There you go, being all rational and holistic about the problem. I had hoped someone would do that.
The mounts are and have always been in pretty good shape but I have been thinking about a set of prothane or urethane mounts as long as I am up on blocks anyway. That would be a good place to start. The alignment is also a very interesting thing; I shall check the alignment with no clamp and see where things hang. It should be pretty close to spot on with no clamp at all.

 

[IOPort51]

Don't forget the liberal amount of graphite that should be applied on the metal to fiber conections.

I am not doubting what you say but why would I lubricate something I do not wish to move? Or is it necessary to allow it to move?

 

[CJ]

When you do get a 'flex', the joint slips a little. Most exhaust flange gaskets are already impregnated with a lubricant.

 

[elwood blues]

You're looking for a new one of these?

NAPA part #EXH 31404
$6.99

 

[elwood blues]

When I replaced my exhaust manifold, I resisted the desire to go with a header also, I bought a new one. The new one's, although not quite as well built as the original, got rid of this problem by incorporating the donut into the casting in the manifold.

 

[Kane]

sounds to me like a junk yard trip is in your future for a newer manifold. That might be easier way to go

 

[IOPort51]

anybody have a clue what years would have the cast on donut and the air injection ports??

 

[Kane]

I snagged mine off an 81 I think. I didnt need the air ports so I cut them and sealed them. Oh I bet the 86 to 90 carbed wranglers have them since it was the same motor. Those might be easy to find in a scrap yard.

 

[IOPort51]

I snagged mine off an 81 I think. I didnt need the air ports so I cut them and sealed them. Oh I bet the 86 to 90 carbed wranglers have them since it was the same motor. Those might be easy to find in a scrap yard.

I will not swear that the intake on my 81 J-10 is original but it has the donut but not the injection ports. Do we know when they quit using that stupid air injection system?

 

[Kane]

Now I am getting confused. I thought the ports were part of the aweful emmisions set-up that never went away. I have had my AMC 258 i6 / 4.2l in 8 years so I am forgetting things now.

 

[IOPort51]

Now I am getting confused. I thought the ports were part of the aweful emmisions set-up that never went away. I have had my AMC 258 i6 / 4.2l in 8 years so I am forgetting things now.

I can not honestly answer that. I think it did but I don't know when and the emmisions system was never a hot topic for conversation. I know the cat converter came on CJ's in 78 but obvoiusly that didn't replace the "smog pump". as I said the J-10 does not have the ports but it was put together by a series of shade trees from a series of trucks before I ever got it.

 

[elwood blues]

I will not swear that the intake on my 81 J-10 is original but it has the donut but not the injection ports. Do we know when they quit using that stupid air injection system?

Not sure when they stopped using the air injection system, but I know in either '80 or '81 they switched the design of the exhaust manifold on the AMC 258 i6 / 4.2l . The '79 and older ones have the exhaust heat flap in them, the newer ones don't. All of them I've found have the holes in them for the air injection ports.

Here's a picture of the '80 and newer AMC 258 i6 / 4.2l exhaust manifold for reference. I'm almost positive when they switched to the newer style manifold they did away with the donut.

 

[IOPort51]

I do kind of wonder where the manifold on the truck came from but you are more than likely right about the 1980 changes. just have to keep that on the list.

 

[elwood blues]

When I replaced my exhaust manifold I did a lot of research. I read somewhere that with a little modification the newer style exhaust manifold will fit on the older heads. There is one line-up stud on the head that needs to be ground down to make it fit. But the biggest issue is that the older style intake manifold bolts directly to the older style exhaust manifold, the newer style is two seperate units that do not bolt together.

 

[W7NB]

I'm not sure on the YJ's after they went to the 4.0, but I know the CJ's and YJ up til 1990 had the same manifold with that air system.

 

[LongHorn]

I can not honestly answer that. I think it did but I don't know when and the emmisions system was never a hot topic for conversation. I know the cat converter came on CJ's in 78 but obvoiusly that didn't replace the "smog pump". as I said the J-10 does not have the ports but it was put together by a series of shade trees from a series of trucks before I ever got it.

Hey IO, what is this strange emissions thing of which you speak?
Do they emission test 30 yr. old Jeeps in Garland?

 

[IOPort51]

Hey IO, what is this strange emissions thing of which you speak?
Do they emission test 30 yr. old Jeeps in Garland?

The tribal wisdom is that you should have all the parts you had when it was new.
this is the state position. Weather the people at the emission station will even lift the hood is a good question. On the other hand I have the option of registration in Fannin Co. For the folks in Fannin Co. it's pretty much a case of "do the lights work? that will be $XX".