Best year for Jeep 4.0 Exhaust Manifold? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 10-20-2002, 04:59 AM Thread Starter
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Best year for Jeep 4.0 Exhaust Manifold?

I have a 94 4.0 engine in my CJ8 using the stock 94 exhaust manifold. As many of us experience, mine has cracked and been rewelded. I can't afford a nice Borla. Hence, when I look at newer 4.0 stock manifolds, 96-02, is there a year I should go after and will the newer stock 4.0 manifolds bolt to my 94 motor? Thanks
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post #2 of (permalink) Old 10-20-2002, 08:38 PM
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Re: Best year for Jeep 4.0 Exhaust Manifold?

I had the same problem. The OEM part is up there in cost with the after market headers as it truly is a header it's self. Then I found http://www.bishopengine.com/pages/ei...oductid=C-1533

They shipped it to my door and I bolted the manifold in with NO mods to my exhaust system. I give them my highest rating. (They did tell me that the 4.0 manifold is one of their top sellers. Thanks Jeep Engineers!)

Good Luck!
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post #3 of (permalink) Old 10-21-2002, 07:06 AM
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Re: Best year for Jeep 4.0 Exhaust Manifold?

My '96 manifold is cracked, and I ordered an aftermarket manifold with reinforced welds and built-in flex joints. I got it from 1A Automotive.
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post #4 of (permalink) Old 10-22-2002, 07:21 AM
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Re: Best year for Jeep 4.0 Exhaust Manifold?

look for a Cherokee exaust manifold in a junk yard they are stronger than the YJ ex manifolds. plus they are more like a header
post #5 of (permalink) Old 10-22-2002, 08:03 AM
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Re: Best year for Jeep 4.0 Exhaust Manifold?

My 93 4.0 donor from a Cherokee has a crack in the exhaust manifold also. I don't think that they are that much stronger. I just had it welded this morning here at work. We'll see how long it holds up.
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post #6 of (permalink) Old 10-22-2002, 09:07 AM
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Re: Best year for Jeep 4.0 Exhaust Manifold?

[img]images/graemlins/blush.gif[/img] I stand corrected [img]images/graemlins/wink.gif[/img]
post #7 of (permalink) Old 10-22-2002, 09:17 AM
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Re: Best year for Jeep 4.0 Exhaust Manifold?

I'm not trying to flame you, just saying that I think that it's a common problem for 4.0's with the header style exhaust manifold.
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post #8 of (permalink) Old 10-22-2002, 09:55 AM
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Re: Best year for Jeep 4.0 Exhaust Manifold?

I didn't think you were flaming. I had heard that the Cherokee's was stronger, but I guess not. [img]images/graemlins/grin.gif[/img]
post #9 of (permalink) Old 10-22-2002, 11:41 AM
 
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Re: Best year for Jeep 4.0 Exhaust Manifold?

My '98 is cracked, still trying to figure out what to do, replace, weld etc.

My friends ZJ also has a much worse crack than mine. All in all I think most of the stock 4.0L exhaust manifolds were pretty weak.

Rob
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post #10 of (permalink) Old 10-22-2002, 02:46 PM
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Re: Best year for Jeep 4.0 Exhaust Manifold?

Definitely replace. Welding the manifold is only a temporary fix. It'll break at the new welds in no time.

Here's the problem - they ran the exhaust manifold close to the driver's side motor mount. This causes premature wear to the motor mount, and excessive movement of the driveline. This stresses the exhaust, and causes the manifold to crack. Usually in one of two places:

1. At the rear stud of the manifold (at the firewall). Usually the whole stud just breaks off.
2. On the top side of the pipe closest to the block at the collector, just before the weld.

Go with either headers or an aftermarket manifold with the flex joints and reinforced welds. A new OEM manifold will only buy you a few more thousand miles before it cracks again.
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