As to be expected, my '96 XJ has an exhaust manifold full of cracks and I am considering replacing it wth one of those manifolds that has two flex sections in it - I think it's Dorman. Any comments?

 

That should be fine,But a lot of the cracking problem is bad motor mounts letting the engine move around to much.

 

Those are the ones that come on the '00 and '01's if I am not mistaken. The ones using the 0331 head. On those heads one of the ports are larger, can't remember if it is intake or exhaust, then on the head you have. Thinking it is exhaust and wondering if this will create any leaks if you try and do it.

 

all of the ports on the 0331 head are smaller than the previous years.

OP: if you do not want an aftermarket header for it i'd look for a factory pre-00 manifold. have someone check and then repair if necessary. install new motor mounts (prob just the drivers side is bad) and carry on.

 

Thanks to all for your replies. Since the head that uses the flex manifold apparently has ports either larger or smaller than the 1996 head, I'll use a different manifold.

Is exhaust heat the reason for the common motor mount failure on the left?

 

i don't think so. the natural torque of the engine is most likely what kills the mounts. they are very easy to change with the exhaust etc out of the way. if i had my factory one removed i'd offer it to you. i had a crack near the collector welded a couple years ago and put it back on. it has been fine. i have a full on new exhaust sitting in the garage patiently waiting. coated long tube header, downpipe, muffler etc. not enough motivation to mess with it yet.

 

STOP!

Ignore what was posted above about the 0331 head. It doesn't apply to you. Those folks were well-meaning, but were waaaaay off the mark.

Is this the Dorman manifold to which you were referring? If so, it also has nothing to do with the 0331 head and will work just fine for your 1996 XJ.

http://www.rockauto.com/en/moreinfo....180314&jsn=377



Heat can contribute to the rubber deteriorating, but so can oil contamination, and more than anything time does it on its own. Motor mounts are maintenance items that need to be changed periodically anyway.

If you have a cracked manifold, do replace your motor mounts. Even that Dorman manifold with the flex joints can crack if the engine is moving around too much. Also, if your motor mounts are shot, chances are good your transmission mount has collapsed as well. You need to loosen the tranny mount to replace the engine mounts anyway, so you might as well just replace it while you're under there.

 

I am not 100% sure about the exhaust port size on the 0331 vs earlier model heads, but the stock XJ motor mounts are just a bad design, I would suggest upgrading to something like the MORE Bombproof mounts, Brown Dog Offroad, or SFR mounts

http://www.stinkyfab.com/heavy-duty-...jeep-4-0l.html

I did motor and trans mounts in one go - just don't get the Anchor/DEA mounts because they are utter garbage

 

The 0331 head has smaller exhaust ports than the prior heads. They were designed that way for better flow with the waste spark ignition system.

But again, 280ezrider doesn't have a 0331 head and wasn't asking about a 2000 or 2001 exhaust manifold. He has a '96, which I believe has the 0630 head. The Dorman manifold with the flex joints he was asking about won't even fit a 2000 or 2001, which is fine since he doesn't have one.

 

I used the dorman flex joint manifold in my 94 mans 99. They have been working great for 6 and 3 years.

 

The motor mounts can go bad for a few reason,Lack of maintenance is a big one,Some people think changing the oil is all you need to do ever.And driving habits can kill them fast also.The people that drive it like they stole it,Aka hold it to the floor and slam on the brakes hard over and over.That will eat the motor mounts in time.

 

Yes, this is the Dorman manifold I am referring to. Thank you for clearing up the confusion.