Exhaust Header Questions

Hi,

I'm diving into my first major DIY mod on my 1997 Cherokee SE. i've been living with a cracked exhaust header for years, and I'm ready to replace. I've searched a lot of great threads on this site for how to do the replacment, but I can't find much on what header to buy. A couple of questions the experts might answer to help me downselect.

First, what's the advantage of a ceramic coated header? Why would I pay for this?

Second, seems like I can spend a lot of money on a Gibson or a Borla header, or about half the price on an APN. I'm going to stick with my stock cat-back system. What's the reliability of the APN's in comparison with the Gibsons or the Borlas?

Seems like an important factor in durability is mounts. I had mine replaced at about 100K, and am now at about 170k (mostly road driving the last 30k). Should I be worried about replacing these again?

Any advice is appreciated!

I use the Brown Dog natural rubber mounts for the engine. You can change them to poly if you want, and you can re-build them. Brown Dog also has HD brackets for the engine. I'm running a Daystar poly trans mount, I like the stiffness it provides.

The APN header is really well built, quite robust at the collector: http://www.ineedparts.com/index.php?target=products&product_id=15343

Adding in a flex tube section in the downpipe before the CAT--where it crosses from left to right, removes stress from the header: http://www.cxracing.com/mm5/merchant.mvc?Screen=PROD&Store_Code=CXR&Product_Code=FLEXPIPE-250x8

Search for Borla info. Some have had great luck--some say they are not so good. Haven't seen much feedback on Gibson.

Thanks, Joe. I was hoping to get more feedback on the gibsons, and why I'd want to pay more for a ceramic coated header. Looks like a lot of people have good experience with the APN's, and I'll probably go with that.

The downtube is a good suggestion, but looks like installing it is out of my league (I'm not a welder). Besides, i'm not planning on changing my crossover pipe or cat back system.

I've seen on other threads that some folks have had APN's crack. Any comments? Any reason I shouldn't by an APN?

Cracking is many times caused by bad motor mounts or trans mount. Also, as Joe suggests, a flexpipe reduces the chances of cracking due to stresses put on the exhaust manifold/header from the rest of the exhaust system.

Good mounts, OEM or aftermarket, and the flex tube no matter WHAT header you decide to use, or odds are you will need to replace it again a lot sooner than you had expected too.

The exhaust layout and exhaust hangars are too solid for the amount of flex that the unibody and engine/transmission torque will apply to it.

How much torque/flex is there? Well, the 4.0 in the XJ in my experience likes to break/loose more engine mount brackets bolts, and go through OEM motor/trans mounts more than most vehicles I have had the pleasure of working on. And unibody flex--well, when you wheel and then can't open/close the doors and hatch--that is a pretty good indication of things twisting around.

I have seen one post of a cracked APN without comments as to the engine mount/brackets or trans mount, or if a flex tube section was installed. IMHO the APN replacement header is very well built and will last a very long time if the brackets/mounts and flextube are maintained.

Good luck.

One notable exception was my Brother's 1966 Mercury Cyclone with the 390 and automatic. The driver's side mount would bust every couple of months just when you happened to really stick your foot in it. Of course the engine would rear up and stick the throttle at WOT--a little hairy when that would happen around town. We ended up welding chain to the frame for a limiting "strap".