How has your OE Mopar exhaust manifold held up?

TJRick

TJRick

TJ Enthusiast
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Most of us with 1997 - 1999 Jeeps with the 4.0 have had to replace our [one piece] exhaust manifold due to cracking. Unlike the stock piece, the MOPAR replacement has accordion joints to solve the problem, and it costs over $400. Aftermarket replacement manifolds look the same and they are typically $150. But in reading the reviews, it seems that many of these are also cracking. I am a firm believer in that you get what you pay for, but is the MOPAR replacement a better piece? Is it made in the USA?

Is anyone actually using the MOPAR exhaust manifold over the cheaper chinese knockoffs? If so, how has it held up?
 
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@Jerry Bransford either has on his current TJ or his old TJ had the MOPAR replacement. I went through 3 aftermarket ones , one ebay special and two from Dorman before I went to the upgraded design from ATP which is more of a header. Its been one about 18 months and I currently have an exhaust leak. Im hoping its just the gasket as I dont see any cracks but if it is the manifold I will be buying the MOPAR replacement.
 
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Seems like many people's OEM manifolds are cracking or we wouldn't even be having this discussion, right? That being said, I've had the OEM, Borla, and recommended on this forum ebay with expansion sections all crack. I now have a Doug Thorley newer style two piece header and haven't had an issue yet. Also, its an upgrade. Because race car.
 
Skylinessuck said:
I guess I never got around to my main point which is I think the newer style two piece ones solved the issue.
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The newer two piece style did fix the issue. However they also changed the shape of the exhaust ports on the head at the same time they changed to a 2 piece manifold. You can install the two piece manifold and head pipe if you wish but it blocks part of the exhaust port which is why MOPAR added the flex joints to their manifolds for 99 and older instead of just retrofitting to the new two piece manifolds. And chances are if you installed the 2000 and up header as thats the only two piece Doug Thorley makes the shape of your header doesnt match the shape of your exhaust manifold. Which is why American Racing Header builds their header to fit both styles of heads and why the Edlebrock aluminum head calls for the 99 and older style manifold.

Im sure people do it all the time but there is a reason the MOPAR engineers didnt.
 
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I am aware of the exhaust port difference from the 0630/7120 to the 0331. Most aftermarket headers (Doug Thorley included) have the larger ports to suit both. I wouldn't strangle the P&P head on my stroker with something that blocked the ports ;-)

Those recommendations from Edelbrock assume you are using a stock manifold I assume.
 
Skylinessuck said:
I am aware of the exhaust port difference from the 0630/7120 to the 0331. Most aftermarket headers (Doug Thorley included) have the larger ports to suit both. I wouldn't strangle the P&P head on my stroker with something that blocked the ports ;-)

Those recommendations from Edelbrock assume you are using a stock manifold I assume.
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Most people are not aware. If Doug Thorleys headers do in fact work with the larger ports than thats something I will look into on mine as I need to redo the whole exhaust anyway. so Thanks for that info.
 
Skylinessuck said:
I am aware of the exhaust port difference from the 0630/7120 to the 0331. Most aftermarket headers (Doug Thorley included) have the larger ports to suit both. I wouldn't strangle the P&P head on my stroker with something that blocked the ports ;-)

Those recommendations from Edelbrock assume you are using a stock manifold I assume.
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Are you sure about that? I mean, I hope you didn't say that just to "win" an argument.
 
You mean reference the exhaust port size on the DT headers? They matched up with the manifold gasket for my head (which has been P&P by Russ P and also matched the gasket) with no blockages. If I'm not correct, then I have a lot more to worry about than not winning an internet argument---and I didn't even know we were having one of those. Seemed like a good discussion to me.

Do you know something I don't?
 
Skylinessuck said:
You mean reference the exhaust port size on the DT headers? They matched up with the manifold gasket for my head (which has been P&P by Russ P and also matched the gasket) with no blockages. If I'm not correct, then I have a lot more to worry about than not winning an internet argument---and I didn't even know we were having one of those. Seemed like a good discussion to me.

Do you know something I don't?
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No, I just never heard of anyone else running the two-piece Doug Thorley headers in place of the one piece unit. And that sounds like a great option. What other modifications (if any) did you have to make to get this to work?
 
I had a custom 3" exhaust fabricated from the header(s?) back, but there is a replacement Walker pipe that mates right up to the 2 piece headers if you don't mind the stock pipe size and crimp bends. You would just need to figure out the 2 bolt flange to the cut off pipe mating just in front of the stock catalytic converter. I did that just to drive to the exhaust shop by chopping off the flange and putting one of those clamp patch things. That was all before I bought my super awesome $90 harbor freight welder lol.
 
Here is the ATP from AutoZone I just pulled today. The metal is not cracked but the welds did not hold. This manifold is sold as the upgraded version to the OE style Doorman manifold they also sell. This one was installed about 18 months ago. So this is another issue with low end manifolds. Low quality welds.

IMG_20200506_120502.jpg
 
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My 97 is cracked where it meets the downpipe. Just recently too and I am at 130k+ miles. I plan on replacing it soon. Ive read the cheap ebay manifolds will work as long as it has the steel accordian flex joint, and the downpipe also has a similar flex joint. Watching this thread...
 
I have used a Crown manifold on the daughters 99 xj. Been over a yr so far. And I did coat it with Eastwoods Paint for manifolds.
 
tworley said:
My 97 is cracked where it meets the downpipe. Just recently too and I am at 130k+ miles. I plan on replacing it soon. Ive read the cheap ebay manifolds will work as long as it has the steel accordian flex joint, and the downpipe also has a similar flex joint. Watching this thread...
Click to expand...

I don't think I have ever seen one with a flex joint in the downpipe.
 
TJRick said:
I don't think I have ever seen one with a flex joint in the downpipe.
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I think it was a flex joint someone installed/welded to their downpipe. I'll see if I can find it...
 
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I have one of those cheap ebay Chinese accordian style ones that I installed over 10 yrs ago. (The OEM Jeep manifold cracked)
For some reason, surprisingly to me, it's still solid.
...keeps fingers crossed I didn't just jinx it...

I'm sure I'll have to replace it at some point.
 
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I did some research on this one, and decided to pony up the extra money for a genuine MOPAR exhaust manifold, part number 4883385. This one cost 3x what the aftermarket offers, but I hope this turns out to be a case of "you get what you pay for." The manifold arrived today, but I have not installed it yet. I will let everyone know if it was worth the extra bacon or not.

According to the MOPAR box it arrived in, this manifold is made in the U.S.A. :)

All of the others are made in China. (n)


What is interesting is the different weights of the replacement manifolds. All of them have the flex/expansion joints:

MOPAR - 16.9 lbs.
Crown - 15.17 lbs.
Dorman - 14 lbs. (includes hardware and gasket)
ECCPP - 14.57 lbs. (stainless steel, includes hardware and gasket)
Omix-ADA - 14.67 lbs. (includes hardware and gasket)
 
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If your engine mounts are shot, even a nice well-made header will crack in short order. Make sure engine mounts are good, and use a header with the flex joints on it along with adding in a section of flex pipe down stream before the cat converter which will help reduce stress on the header.
 
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