Bowtie7

Ok 1st I think this a great site with lots of info and has helped alot. Still have a few questions. My Cherokee is an 89 and it has the I6 auto 4x4.I have no paperwork and no tags on it.Just want to make sure its the 4.0. Been reading about a 4.2 but no knowledge of what this engine is and what it came in. Next the exhaust manifold is cracked on mine and looked at 3 other similar years at the salvage yard and they are cracked to.Is this a common problem with these years and what is the best fix?Finally I replaced RMS and pan gasket with 1 piece rubber gasket(blue one) and did the same on Valve cover. Still has small leak in rear of VC. I noticed on the cast aluminum VC that it had half moon lips at the bolt holes and being as the gasket has metal rings in the rubber of the gaskets, do the half moons need to be ground off to make a proper seal. It dont seem to be leaking anywhere but the back next to the fire wall.Thinking maybe the half moon lips may be allowing the gasket to leak. Any help is greatly appreciated.

EVcherokee

If its the motor that came with your rig and its a I6, its a 4.0l. AMC never used the 4.2, more commonly called a 258, in XJ's.

The exhaust systems on these rigs were poorly designed, and the manifolds cracking is one of these design flaws. The manifolds are steel and the best way to deal with them is to just weld the crack up. They can re-crack next to the weld, but I don't think its too common, just watch your heat. Making sure your exhaust is secure at the the tranny cross member and not flopping around will help prevent re-cracking. Welded mine up last year and no problem so far. Using a THIN(construction paper thin) layer of high temp copper RTV, will prevent exhaust leaks between the manifold and the head, not to mention vacuum leaks. Installing a $100 cat-back system will free up a lot of pony's and help your MPG's. As long as you keep the manifold to cat pipe, you'll maintain enough back pressure to keep your low end torque, the rest can be modded how you like....within legal limits...

I'm not to sure about any half moons on the valve cover, I can't remember what mine looked like.

TheJerm

Take a ball peen hammer and hit the holes on the mounting surface, this will make the area between the bolts the low point and when you tighten down the bolts the seal will be better. This works with diff covers too

APN header - good cheap header replacement with lifetime warranty

Bowtie7

Welding it up was my plan for a temp fix.I really hate having welded up exhaust on anything.Ive welded up cast manifolds and headers and just knowing its there bothers me, but that is my next step.Is there pro or con to SS headers? My dad put them on his wrangler but Im curious about effects of hot /cold up and down temp range of SS.Will it last? If so I may do the entire exhaust from header back. Im looking for reliability in my rig. As far as tapping VC with a hammer that dont work so good on cast aluminum.Works great on steel everytime. Thanks guys!!!!!

JeepCoMJ

uh.

where the F do you get your information?

there was NEVER a 258/4.2 in an xj

fsj, sure. but never an xj. the I6 in an xj wasn't introduced until 1987

1ATony

The problem is over time the exhaust manifolds become brittle and crack from heating up and cooling down. It happens on quite a few trucks also.

EVcherokee

Your right %100, they we're never in XJ's, got my info mixed up between the FSJ and the XJ. Thanks for the correction.

JeepCoMJ

no prob. sorry if i sounded like a dick...not trying to be.

Bowtie7

Ok its a 4.0. I thought it was but kept reading about the 4.2 so thought I would ask and hoped I didnt sound like a dipsh-t. So as far as manifold vs header, I know a header may build a little more HP but Im looking for long term reliability. I keep hearing about both cracking so I guess my question is if this is a common problem with the jeep.If so is the culprit the movement of the exhaust or from the heat. We dont have any cat laws here(yet) so I want to do the whole exhaust. Wont really be using it as a trail rig but more for a daily driver and hunting rig but I plan on really fixing it up to be durable. You guys been messin with jeeps a while so what would be my best bet.

freegdr

get the headr make sure theres a o2 bung on it and your set for further mods such as exhaust and stuff related

EVcherokee

Cracking is a common problem and usually happens once. I recommend you just weld up the crack and keep truckin. If you don't have to pass emissions, it would be a good time to yank the EGR system, for a couple more
hp and a smoother running motor. From what I've read, there aren't huge gains in installing a header, because the manifolds actually flow descent, but maybe someone who has put one on will chime in.

Cat laws are federal, not state or local, and we're not allowed to talk about it here. I can't recommend it for that reason, but I can say the cat holds back a lot of pony's. Most of the restrictions in the exhaust are in the cat and back to the tailpipe. An aftermarket muffler with a 2 1/2" mandrel bent pipe going back from there will get you a good 20hp. Keep in mind too the better your exhaust flows the cooler it will be, because more heat goes out the tail pipe. If you replace the pipe going from the manifold to the cat, your going to lose backpressure along with your bottom end torque. Google search can find you tons of info on this subject.

TheJerm

20hp from increasing the exhaust 1/4 of an inch? seems like a far stretch.

If your worried about it in the furture, have a muffler shop weld in a flex tube between the manifold and cat. It will reduce the vibration stress on the manifold

edit: i really enjoyed having a 99 intake and header on my 95, when my header cracked from the front yoke (my fault) I put a stock non-cracked manifold back on and i could feel the difference. Just not as much get up and go, still went but not as much fun

Bowtie7

You guys pretty much answered my questions.Im not looking for big HP so I am sticking with the manifold and going with new slightly larger exhaust pipe.Gonna run a good flowmaster muffler.I have found a stainless steel manifold on ebay for about 130 bucks.Would this be a good investment of should I stay away from stainless and keep factory manifold and just fix it. Money aint the issue to a point, just want good parts.

mjs302

Don't try this with a cast aluminum valve cover unless you want to buy a new one. This trick does work well with stamped steel covers though. It's also good for steel oil pans and steel transmission pans.

EVcherokee

20hp is the number I've read in a couple places and I believe it. A 1/4" makes a big difference when your going from 2 1/4 to 2 1/2, not to mention the mandrel bends and the aftermarket muffler. Its all about CFM's. I installed a flowmaster 40 with mandrel bent 2 1/2 going back from there and I've noticed a big difference. My exhaust runs cooler too.

If you weld in a flex tube, add hangers to both ends, because if both ends can move, you might have problems with joints coming loose and more cracks. Also flex joints don't flow well, so you may negate any upgrades by installing a flex joint.