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APN Header Photos


NAXJA Forum User
NAXJA Member
4.0 Exhaust Manifold Installation



remove Airbox

cover Throttle Body

remove Electric Fan

reduce tension and remove Serpentine Belt

remove Power Steering Pump

disconnect Fuel Line at Fuel Rail
spray new Gasket with Copper High Temp Adhesive Sealant

Cylinder Head prepped

Copper sprayed Gasket resting on alignment pins
Get Grease on Shutter so remaining photos are ruined




Good info! As someone who's been through this recently (several times on my Jeep and a couple of others), while you have the header off and everything out of the way, take a good look at your motor mounts, especially the drivers side. If they are in bad shape, your new manifold will crack eventually. Mine lasted about 6 months and this is why:


Great time to replace them is while you already have everything off. Even if you don't have much money and want to go with OEM replacements from your favorite parts house vs. ordering after market ones online.
If you look in his pictures, he already replaced the motor mounts with some type of aftermarket unit. Look like M.O.R.E.s.

Good advice in general though :thumbup:
No need to modify the #6 header pipe? Any intake leaks to speak of following the install?

No leaks and no modification to the manifold (I still have the old style intake on my 97).
I'd like to upgrade to the later model intake with the larger plenum chamber someday.
I'll update how things piece back together when I get around to it.
Fair warning - that might be years from now.

: )
I did want to mention that I was surprised at the improved throttle response.
The mud terrains will chirp and break loose with much less persuasion from the skinny pedal now.
I reset the throttle cable and the CPU as described on go-jeep, I believe this helped a lot.

The APN header also gave the 4.0 a very pleasing throaty rumble.
Of course, it is much quieter than the stock header with that crack!
Under hood temps have also notably dropped.

Highly recommended.
Man I wish I could get the APN header, but since I have a '00 I need to spend the money on a BANKS!

So, headers do improve the 4.0's power? Im completely stock (exhaust wise :)), so If I ever go for a header, Ill probably go full 2.5" all the way out.
Interesting claim on the results.

I didn't notice any better throttle response, no cooler underhood temps, and no more "rumble" than stock.

Not trying to disprove your claims, just interesting that they differ so widely. I also did a 99+ intake at the same time on mine.