After much research, the overall conclusion seems to point out that the header component on the 4 banger yields little benefit. After going with a bored tb, air intake, magnaflow hi flow cat and turbo muffler I figured to round out all the add ons the banks header was the answer. I have already been so impressed by the additions so I decided to buy another banks header (already have one on the xj and love it! 4.0 btw).
The header costs roughly the same - about 350. The little guy is built like its bigger brothers: 1/2 flange, mandrel bent tubing and double tig welded throughout the whole piece and stainless tubes I believe. An added benefit is that it weighs considerably less than it stock counterpart: I would say a good 10-12 lbs less. The stock cast unit is almost like a boat anchor compared to the banks. Anyways having done this on a 6 cyl even though I vowed NEVER TO DO ONE AGAIN!! (can't you tell how much i love installing headers?!) I figured more space and 2 less cylinders would make it ok. Luckily my motor is like new with 8k on it (140k on body) - a very clean 01 TJ with zero rust. I hit everything with PB blaster just to be safe two days prior to install.
About 3 hours later taking my time with a buddy we were done! I have done this before which helped throughout the install we were chilling, drinking cold adult beverages and cruising really through the install. The only slip up was the donut: first round of tightening the downpipe up the donut did not sit right causing a exhaust leak. A little rearranging and we were good. My manifold gasket even looked brand new - oh ya it is. Anyways straight forward install. Here are my 4 cyl notes post install:
PB blast every bolt prior!
Do not forget about the two bolts under manifold: by taking off power steering pump, belt and some assorted wires you CAN get to these bolts. A good swivel socket is a must. Make sure you tighten them snug and be patient: they can be hard to get to.
Graphite greased lithium whatever donut will smoke and smell for a couple minutes while motor warms up. This is normal: keep hood open and I like to have a fan handy to blow it out of your work area.
Nothing was metric that I can remeber: 1/2 and 9/16 mostly on the hardware. My bolts looked good and reinstalled them with anti seize (same on xj with 100k) but some people do replace bolts for piece of mind. Just do a good inspection while they are out.
Always disconnect neg. side of batery so the computer can relearn fuel curve.
Manifold has two studs it sits on which is a good benchmark/ visual for reinstall of gasket and manifold.
Impressions:
A little more throatier exhaust tone.
1k - 3k RPMS seem to rip through smoother and faster.
Idle is crisp and smooth - great with hi flow cat and exhasut system at idle.
4th gear and 5th gear - most improvement on top end! I can hold 4th longer before shifting and 5th seems to use less rpms at highway speeds of 65-70.
Little more pep in throttle.
MPG - will report back.
Overall thoughts:
Fit: 5/5
Performance: I think banks headers are the best: but 4 cyl benefiting from almost 400 dollar product? Maybe a couple horses and torque points: 4/5
Cost: 2/5 - pricey
I really love the way my TJ drives but it has taken doing a lot to the motor. the banks header is not needed but if you really love your 4 cylinder or have the cash laying around it go for it. To be honest, i think I would have rather bought a set of aussie lockers. I really do like it though and now have a complete full exhaust on my TJ.
Not a great bang for the buck but banks deliverers a bad ass header and will help any 4 banger out there.
