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Unread 09-15-2014, 04:42 PM   #1
Cobra Jeep
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1993 YJ Wrangler 
 
Join Date: Aug 2005
Location: , Alabama
Posts: 1,219
ZJ exhaust front pipe swap

So I recently aquired a 94 XJ. It needed a little work here and there. Couple things were the factory manifold being cracked and it needing a muffler.
So crawling around under it inspecting things, I noticed the tiny front pipe. I also noticed the dent where it connects to the header. I noticed it again when I changed out the cracked header. I noticed it was almost pinched off halfway and thinking this cant be good for performance. I thought it was damaged at first, but a little searching on here found it was factory. Couldnt really find anything about replacements, other than having a exhaust shop build a new one. Or a stock replacement. I read that the stock replacements didnt have the dent. I find one made by walker exhaust on amazon. The picture showed a nice looking pipe with smooth bends. I order one up and there is no dent, but it had those crimp ribbed style bends, the pipe is still tiny, and the hanger for the trans crosmember is just a cheap flat peice of metal, instead of the sturdy curved factory one.
So now I'm back to square one. I thought about making one from pre bent sections, but that was going to be too much of a pain. But then I got thinking, what about the 4.0 ZJ's? I couldnt find anything about a dent on those. So next time I went to the local pull a part, I started looking for a zj. I finally find a 97 with a 4.0. I look at it and no dent, pipe is larger sized, and where it goes under the trans, it gets larger. It looks to follow the same routing at the XJ, and it even had the bend to go over the trans crosmember. I figured why not, I will give it a try. The yard cuts tha cats off when they come in, so all I had to do was unbolt it from the header.
I get back home and get to work. I had already purchased a dyomax super turbo cat back kit, so I was already going to have most of the system off.
I go ahead and pull the front pipe and lay them side by side. They match perfectly! Only problem I saw was the hanger being in a different spot.
Picture: XJ in the front, ZJ in the back



No big deal, I can cut off the ZJ hanger, cut off the XJ hanger, and weld the stock XJ hanger onto the ZJ pipe. So I cut off and grind down the ZJ hanger. I cut off the stock XJ hanger with a 4.5 in angle grinder and a cutoff wheel. I grind the weld and get the rest of the pipe off it to get just the bare hanger. I test fit on the pipe. The ZJ pipe is bigger, so a few hits with a BFH on a flat surface opened the hanger up enough for the new pipe. I insert the haanger back into the trans mount. I then test fit the ZJ front pipe. I bolted it up to the header and set it on top of the hanger. Perfect fit! A little positioning to get it setting right and I tightened down the header bolts locking it in place.
The ZJ front pipe is 2.5 OD. So I simply got a 2.5 to 2.25 reducer at the local parts store. A little cutting and grinding and it fit into the inlet of the stock cat. I then bolted on the rest of the system and welded everything up.

All and all it was basicly a bolt on deal with the exception of the hanger on the trans mount. I must say, it has definatly woken the 4.0 up. Awesome sound, more power and a better flowing front pipe.

More pics. Sorry for the glare, it was really sunny and I was having a hard time getting good pics. But you can see how it all lined up perfectly.







__________________
'93 YJ 4.0L, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, WJ knuckle/brake conversion, hydroboost. Warn M10000 winch. Hope to some day build a stroker for it.

'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.
Future mods: NV4500, NP205, high pinion D60 front and smooth bottom D60 rear, e-lockers front & rear. SOA with 35X12.50's
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Unread 09-16-2014, 12:08 AM   #2
GrnJeep
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1999 XJ Cherokee 
 
Join Date: Sep 2010
Location: Tuscumbia, AL
Posts: 179
Any smoother idle or running?
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Unread 09-16-2014, 06:11 AM   #3
Cobra Jeep
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1993 YJ Wrangler 
 
Join Date: Aug 2005
Location: , Alabama
Posts: 1,219
Well, like I said, I installed this at the same time as the dynomax cat back. I could definitely feel the difference. Now I don't know how much was from the cat back and how much was from the front pipe. But I know the front pipe did not hurt anything, and you know it has to flow way better than the tiny pinched off stock front pipe.
If you just swap the front pipe and leave the rest of the system stock, you might not notice much difference. Now if your wanting a better flowing/sounding exhaust and are installing a cat back system, I would recommend this at the same time. Its a cheap and pretty easy swap.
__________________
'93 YJ 4.0L, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, WJ knuckle/brake conversion, hydroboost. Warn M10000 winch. Hope to some day build a stroker for it.

'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.
Future mods: NV4500, NP205, high pinion D60 front and smooth bottom D60 rear, e-lockers front & rear. SOA with 35X12.50's
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Unread 10-24-2014, 06:46 PM   #4
miceanic
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1990 XJ Cherokee 
 
Join Date: May 2011
Location: wrightstown, Nj
Posts: 414
Did you install this on a 4wd XJ or 2wd? I don't see a drive shaft or differential on your rig. Would be a nice mod to do when I get bored sometime.
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Unread Yesterday, 03:59 PM   #5
Cobra Jeep
Registered User
1993 YJ Wrangler 
 
Join Date: Aug 2005
Location: , Alabama
Posts: 1,219
Its a 2wd XJ. But the ZJ I pulled it from was 4wd. I don't really see why this wouldn't work on a 4wd XJ.
__________________
'93 YJ 4.0L, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, WJ knuckle/brake conversion, hydroboost. Warn M10000 winch. Hope to some day build a stroker for it.

'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.
Future mods: NV4500, NP205, high pinion D60 front and smooth bottom D60 rear, e-lockers front & rear. SOA with 35X12.50's
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