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Unread 12-29-2007, 10:42 PM   #1
marinjeepfan
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Successful install of two piece manifold (2000-) on 1998

After living with my third exhaust manifold crack since new (once on factory manifold, once each on two "improved" aftermarket manifolds with the expansion joints) long enough for my muffler and converter to finally wear out, I decided to try something different and swap the whole setup for the new two piece design.

Chrysler changed the manifold to a two piece design during model year 2000. Apparently through 1/24/2000 they used the one piece design, then switched on 1/25/2000 to a two piece design with a "Y" shaped pipe from the manifolds to the single catalytic converter and stayed with that through model year 2001 when they added pre-cats to the "Y" shaped portion of the setup.

Since my catalytic converter and muffler were going at the same time, I did my homework on the model year changes and decided (based on what parts changed when) that the "late model year 2000" setup would bolt into my 1998 as long as I switched out everything from the manifolds to the muffler at the same time. I realized I couldn't bolt in anything later then model year 2000 because all the later models require hookups for three oxygen sensors total rather then the two I was wired for.

Long story short, I was able to buy...

A set of Model Year 2000 iron manifolds used on eBay
Walker number 53461 for the "Y" pipe with the hole for the single sensor
Walker number 31625 for the gasket between "Y" pipe and cat
Walker number 16085 for the catalytic converter(*)
Walker number 21456 for the muffler

(*) not 100% sure on this part number

...and with an excellent writeup I found at www.dailydriventj.com on the basic exhaust manifold change, a Sawzall to cut the old parts out, and a whole lot of sweat (and some cursing) was able to bolt in all the parts as expected, no welding.

Most of my research was done in Walker's excellent online catalog at www.walkerexhaust.com, entering the different model years and looking at the part numbers. The local dealer was no help at all, refusing to participate in or discuss any "modification" to the vehicle.

A few notes:

I did have to extend the wires on my upstream oxygen sensor by about 14" because the hole for that sensor is on the other side of the transmission from the original, so longer reach is needed.

The manifolds I bought used were ported for an O2 sensor in each one, which I wasn't expecting on model year 2000. I had to buy special plugs threaded for those holes (I think it is 22mm taper, exactly like a spark plug, and I could have plugged a spark plug in there if I didn't care about looks). Those plugs were an astonishing $22 each. Maybe I was really sold a later manifold set?

I reused my original tail pipe, and found I needed to use a little 3" long extender (technically an adapter from 2.25" O.D. to 2.25" I.D.) I got for a few dollars at Kragen to make the reach from the muffler to the leading end of the pipe, but I think the reason I came up short at that junction was I was a bit sloppy with the Sawzall work.

The clearance between the leading edge of my new muffler and the skid plate was really tight, millimeters when it should have been inches, so it rattled when the motor shook at startup or shutoff. I ignored it for a while, then paid the local Johnny Franklin Muffler shop $20 to give me a bit more clearance. They just heated the front pipe with a torch to soften it a bit, then pried the muffler back a bit to add clearance. Took five minutes. No problem. No rattle any more.

There really is no gasket either between the "Y" pipe and the manifold downpipes or between the muffler and catalytic converter. All are the "ball and socket" metal to metal style. The only gasket is the three hole Walker 31625 between the "Y" pipe and the catalytic converter.

I would have appreciated if Walker had included the two 10mm x 1.5 pitch nuts needed for the muffler with the muffler itself. I had to buy those, along with three suitably long (30mm) 8mm bolts and nuts to join the "Y" pipe to the catalytic converter. That was it for hardware except for a few 2 1/4" clamps.



I am very hopeful that unlike my past repairs with better and better imitations of the flawed factory design (that all cracked anyhow), this two piece design now represents an improved factory setup will finally free me from this endless cycle of manifold cracks.

One other nice thing in returning to the "factory" manifolds versus the heavy tube aftermarket replacements is that the access to the lower bolts is much more "open" (all are visible and reachable from below) on the smaller cast factory manifolds, so getting to those bolts on reassembly was much easier then on disassembly.

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Unread 12-29-2007, 10:47 PM   #2
Squeeky
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pics?......
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Unread 12-29-2007, 11:50 PM   #3
marinjeepfan
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Sorry, I had planned to take pictures of the whole setup assembled outside of the vehicle (can't see much installed), but the way things worked out a few of the parts were still on-order and straggling in so some parts were already bolted in before others arrived, so I never got the shots. If there is a particular picture I can take for someone with things all assembled, I am happy to. I think the best way to see what the stock 2000+ split manifolds look like is to search for them on eBay where sellers often photograph them off the car. The best way to visualize the fancy "Y" shaped pipe I got from Walker (the one that hooks to the two manifolds, then goes down and around the oil pan following the path of the old pipe to the front of the catalytic converter) is to look at the simple diagram on the Walker site.
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Unread 12-30-2007, 07:40 AM   #4
Wheelin98TJ
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Very good information.

Added to the FAQ.
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Unread 01-18-2015, 09:17 PM   #5
bigman2x4x8
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I'm changing my 2000 TJ 4.0 to a 1999 TJ 4.0 and I;m thinking on using the one dump 1999 manifold. The ports on the 99 head are bigger and round and the 2000 head is smaller and squareish. I fiqured the increase size of the tubes on the 99 manifold would help performaace over the smaller 2000 design. What exhast/intake manifold gasket did you use?? How good does the smaller tube seal to your 99 heads?? It would be so easy to just stay with the double dump 2000manifold and not have to do exhast work on the engine swap. BUT I need to figure what gasket to use or if the difference of head to manifold size would seal. Since you have done this to your TJ how is it doing with the new manifold sealing. Thanks for your help, bigman2x4x8
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Unread 01-19-2015, 05:49 AM   #6
jose_p_adams
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Quote:
Originally Posted by bigman2x4x8
I'm changing my 2000 TJ 4.0 to a 1999 TJ 4.0 and I;m thinking on using the one dump 1999 manifold. The ports on the 99 head are bigger and round and the 2000 head is smaller and squareish. I fiqured the increase size of the tubes on the 99 manifold would help performaace over the smaller 2000 design. What exhast/intake manifold gasket did you use?? How good does the smaller tube seal to your 99 heads?? It would be so easy to just stay with the double dump 2000manifold and not have to do exhast work on the engine swap. BUT I need to figure what gasket to use or if the difference of head to manifold size would seal. Since you have done this to your TJ how is it doing with the new manifold sealing. Thanks for your help, bigman2x4x8
I installed a 2 piece factory manifold on a 97. I used the late model exhaust gasket. They are more robust and the holes match the holes in the exhaust manifold. As you noted the exhaust holes are square not round. I initially tried to use the early model manifold and it did not work.
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Unread 01-20-2015, 07:29 PM   #7
bigman2x4x8
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Thank you so much for the reply. How does the new manifold work compared to the original one dump manifold the 97 had. Did it increase power or fuel economy? I checked my 99 one dump manifold has a crack at the welding and I talked to a friend who owns a muffler shop and he told me the old style was a problem waiting to happen. I'm going ahead and reuse my 2000 new design manifolds. Mine does not have two sensors at the engine side but it does have one in front of the cat. If you think the gasket will not be a problem being smaller and square, that's what I will do also. Again I Thank You for the reply, it probally save me from making a mistake. THANKS
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Unread 01-20-2015, 08:44 PM   #8
Knuckelhead
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Quote:
Originally Posted by bigman2x4x8 View Post
I'm going ahead and reuse my 2000 new design manifolds. Mine does not have two sensors at the engine side but it does have one in front of the cat.
I'd bet that each of those manifolds have an 18mm x 1.50mm threaded hole with a threaded plugs in them...
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