2000 XJ exhaust question

Well, I know the APN header has been mentioned, discussed, dissected, and hailed here many times over. In addition, the tech depth of this issue is actually very well documented in this site, but there is still one last bit that I'm hoping the real "experts" can help me out with here. My situation is as follows:
I have a 2000 XJ Sport that has the non-California emissions system on it. As far as I can tell, everything is bit for bit the same as the 97-99 models in terms of exhaust. Obviously, I'm stuck in the coil rail boat, but that's OK with me.


Now, I have heard things about the APN header not working with the 2000's and up, but the general consensus is that this is primarily due to the stupid emissions system on the newer motors. All things considered (I do have a coil-rail casting head, but not more than 1 cat, and the normal O2 locations, etc), do you guys with this header think I have a good probability of a successful install with little to no extra mod work required?




And before someone brings up something about a better design on the exhaust manifold making mine less prone to leaks and cracks, it should be noted that although it took one hell of a lot of work, I still managed to crack this sucker. Maybe I'm special, maybe it's just a 99 carryover, either way, it's not too bad now, but I don't want it to get any worse.

Inquisitive first post is inquisitive.

From what you say, it sounds like it should work fine, and I would try the install.

And worst case scenario you find that it will not work, you could easily find a buyer for the header because everybody eventually needs to replace their cracked one. So go for it.

If anything trips you up, it is going to be the head vs header port pattern. Not sure how that changed from the 0630 (or was it 7120? I do not know much about heads) head to the 0331 head. Compare them and/or check if the 99-down vs 00-up XJ 4.0L manifold gasket changed.

I feel the header for the earlier models will bolt up fine to the 0331 and will have no problems covering the smaller ports. I think if there's an issue, it will be with the header bolting to the downpipe(forget if the non-cali still has the precats). I have a bum 0331 out in the shed and both a HO and Borla header I can dry fit to make sure.

So essentially my best bet for a sure-fire fitment is to make sure the gasket is identical (or close enough) to the pre-00 ones. Also, I need to make sure the DP is the same, but honestly under my hood looks 100% the same as the exhaust write-up on off-road http://www.off-roadweb.com/tech/0610or_1999_jeep_cherokee_exhaust_install/index.html. I do not have the pre-cats on this one, and I know I have federal emissions because my 2001 XJ (cali emissions) ECU throws codes due to the sensors being missing when I swap it into this rig. I'm just trying to eliminate all variables, and it seems like the head casting and downpipe would be the only ones, but I should be good to go. I will likely just buy it, fit it, and pray for the best.

I'm a little confused. I thought ALL '00 and '01 Cherokees had a cast 2-piece exhaust manifold, dual upstream O-2 sensors, and pre-cats. (mine does, and it's from Ohio) The main reason for the 00-up/99/down split was (is?) because the 99-down single piece manifold won't bolt up to the 00-up head pipe, and won't have a place for the second O2 sensor.

I will take some pictures of the stock manifold tomorrow and compare that to the 99 header to see but I'm fairly sure I have the one piece and know for a fact that I don't have the cali emissions setup on this one. It was a major concern when I swapped my o2s out a couple months ago.

When I looked into this, I was told it would bolt on but the reason they say they wont work was because of the 02 sensor and the low pinion dana 30 interfearing with the down pipe after install, Was told if I didnt mind codes going off and had 3 inches of lift it would work,

The bolt patterns are the same between the 00-01s and previous years, it will bolt up. The major problem encountered is that when you replace the 0331 with an earlier head the stock exhaust manifold won't match up enough with the earlier ports. The earlier ports are partially covered by the later manifold. The other way around works better. From what I have heard the earlier aftermarket headers have no problem with the 0331 head ports as the tubes on the header are larger. I haven't verified this myself, but I have heard this from numerous sources.

00-01 XJs cane with both Federal and Cali emissions packages.

The other problem is the O2 sensors and precats. On the cali emissions package the two precats will be eliminated along with the 4 O2 sensors. The earlier headers are longer and the cali down pipe will be cut off. You would them have to do something to replace the cats and the O2 sensors.
With the federal systems it is a lot easier. The after cat sensor is fine, as it is further back. The upstream sensor may have to be relocated, depending on how far the header comes back and how far you have to cut the down pipe off. Not a hard problem to deal with. Have an O2 sensor bung welded in. The down pipe will have to be cut and a a mating flange put on the modified down pipe.

Well, I finally got those pictures. They aren't the best quality and the angles I had to work with kinda sucked, but I think I got what I needed, and am hoping you guys can clarify my theory here.

So, my car has a two-piece factory manifold which was designed to be compatible with the calif. emissions system. Mine is federal. You can see in the first picture how there are separate pipes from each manifold sweeping down past the oil pan:


Now, this is under the intake, where those manifolds meet their individual y-pipe connectors. This is where the cali cats would go normally (like they did on my 01 cali model):



It's not that easy to tell from the picture but the y-pipe consolidates here at the flange for my downpipe. One is fairly well hidden behind the flange.



Here is another view of the same area, better view of the collector:



And finally, the downpipe sweeps around my trans and t-case just like everyone else's, but I think it might still be different.




So, my conclusion I can draw from these pictures, and extensive study of the factory manifold/DP from the 99-down is that the manifold and downpipe are different on my car than on your 99's. I figure the cat is in the same place (after the trans, end of DP) and everything else is identical, so my conclusion is that if I were to put this header on my motor, it would essentially require me to have a new DP built at the same time. I see this as a good thing, considering I hate the free kink that was generously donated to all of us from the factory. If you guys think I'm on the right track here, then it's off to Pontiac I go to get some SS DP action done. I want this fixed, and I want it done right!

By the way, sorry for the huge images, but that's what my phone took.

Yes, you have the federal system. Your stock manifold and down pipe are different from previous years. I'm not even 100% sure on the down pipe, as the Y pipe bolts to the manifolds then the down pipe. You can put the APN or any other header on and be fine. You may still have to have the down pipe modified to meet the header, but at worse you would have to replace the O2 sensor bung.

Do I even want to know what "SS DP action" is?

Do eet!

I guess it's adding up more and more to be my best swap option. I will double check the DP dimensions tomorrow, and try to snap a picture from directly under the rig to give a little better perspective. Hopefully someone on here will have the same or be in a good enough mood to do the same for me and perhaps snag some dimensions, which will really help with the determining factor. This is my DD rig, so the downtime has to be absolutely minimal, therefore I'm doing the heavy research beforehand, to find out if I need to consult an exhaust shop or not. SS DP action is me wanting high quality materials in my downpipe, and refusing anything other than good grade SS. I don't want to ever have to do any of this again, as I'm sure you guys can imagine or relate.

I have the same exhaust on mine. The p.o. welded everything togather on the exhaust. Converter went bad and muffler had a hole in it.So i had to replace everything. I installed a Gale banks header to a stock 99 head pipe that goes to a magnaflow converter,then a 4wd exhaust. Basically what we have is a 00 xj with 99 emissions. They two o2 sensor one down stream before the cat and one after. The part numbers I used are Banks header 51306,Walker headpipe 55277 and Magna flow converter 23226. Hopes this helps