I have seen threads on this before, some say it's supposed to be this way while others say it is not. I crawled under my 99 XJ today and couldn't help but wondering. Is this normal?

 

Yes

 

I used to think there was a lone guy driving all around the country, just him and his hammer doing this in the middle of the night, but everyone says it comes from the factory that way.

 

Alright thank you guys I just wanted to confirm. Man it sure does seem like it would breathe a lot better if that wasn't there. But I guess it's there for a reason.

 

For front drive shaft clearence

 

It has to do with emissions, but I can't remember the exact explanation. I don't believe the aftermarket replacement pipes are dented.

 

I think cruiser knows the origins of the dent. Maybe he'll explain it again...

 

I'm pretty sure monstercherokee hit the nail on the head.

 

its was diguised as drive shaft clearance but it really acts as a pre-cat to warm up the cat faster

if you have a lift (3'' or so) get a Walker Downpipe it comes without the dent and i absolutly recomend doing it.. i have it and have no complaints.

 

Pre-cat isn't really an appropriate term. The function is that it INCREASES back pressure, which has the effect of raising the EGT (and heating the cat up faster).

Jeep Gnomes. They look just like their Garden bretheren but are covered in mud and grease.

 

Sort of out of place, but tossen' in some stuff here. Renix guys, loose the restriction out of your air box. (air cleaner). Big pliers...it WILL come out. DO THAT. AND BOSCH 280 155 746 Injectors. If you find something better let me know. I gained 1 MPG going from 703 to 746. With the restriction gone, got more. Now with the Bosch/Volvo 746, and that gone I'm seeing a for real 16 MPG+ (16.3, 16.4). (gravel, short trips)

I'm pretty good at figuring mileage. I can tell because my numbers are consistent. With the 703's with my o2 sensor dead I got to 11-12. This is allot of short drives in gravel with a few town trips. Now, restriction gone, the 746 (Renix only), I'm over 16 MPG, same short trips, 16+....

273K miles on this girl. Supper looking forward to being able to post solid numbers on what I'd see on the highway. I won't be surprised if it's over 20. It feels really nice.

Edit...I still have the dimple in my header pipe. Since I have an O2/Acc rig, thinking I might just cut it out/patch.

 

Good to know about the Walker downpipe. I have mine made for $50 by my local exhaust shop. They can be made so the driveshaft will not hit even without a lift.

Here's what I just posted on Comanche Club so that anyone who starts spouting the bull**** that we "need" back pressure can be forewarned.

Here's where "old wive's tales" come into play and are usually propogated by those who have never done the mod. . This lower back pressure deal is an absolute crock. That's something that applies to 2 stroke engines mostly anyway.

I will now add that I was advised to do this mod by a Jeep engineer who worked on the 4.0 project. He's the one who told me about "why" the crush is there.
He told me I would feel a "seat of the pants" difference in throttle response and power. He was right.

Don't let the "old wives tales" keep you from enjoying the benefits of this mod.

 

The Walker down pipe is only for 96-99, guess I'm out of luck.

 

Have one made.

 

Has nothing to do with emissions. It's for drive shaft clearance. this is the reason why with they changes the manifold/catalitic converter setup for 00-01 they went to low pinion. Its all about clearance