Originally Posted by mattphillips90

What exactly do you meam HO motor. Not trying to be dumb but I cant figure it out haha. Also yea my manifolds cracked I found them and I had it welded up but it still ticks. I think it may be leaking at the flange because its dented in and I think its not sealing right so I may just need a new flange. Also how will I know if my motor mounts are bad? Thats what I was saying ive looked at but cant tell if theyre bad.

Originally Posted by mattphillips90

But one question, wheres the tail cone mount?

Originally Posted by RenegadeT

HO = High Output, aka 4.0L's from 1991-2001

The manifold is dented, or the downpipe? There are factory dents in the downpipe to give clearance with the front driveshaft yoke.


sandwiched between the transmission and the tranny crossmember

Originally Posted by mattphillips90

Ohhhh just looked that up, guess it's not messed up then. But thanks, that what I though about the mount just didn't know if there was a different too.

Originally Posted by 5-90

#1 - Cracked manifold = Check your Engine Mounts!

Reports from the field indicate that a cracked manifold is almost invariably preceded by engine mounts failing. They don't have to "chunk out" on you, but you'll note that they're really soft. If you're replacing one, replace all three (engine left/engine right/transmission tailcone.)

#2 - The big problem with the XJ exhaust system is that it's very rigid, and relative movement kills it. The best fix? Take your downpipe in to an exhaust shop, and ask them to replace a section of it with a flex joint. That's even better than the aftermarket manifold with the bellows in the #1 and #6 primaries (because it's not the #1 and #6 primaries alone that are the problem.) (NB: This is what I'll be doing as a part of the refit on my 88. I haven't had a cracked manifold yet, but I plan on redoing just about everything anyhow.) I think the later (2000-2001 w/#0331 head and precats) have a split downpipe with a short Wye section - have the flex joint welded into the straight single section instead. This also saves having to wrestle with branches, getting them to line up (since the OEM Wye section isn't disturbed.)

#3 - Exhaust manifold swapping:

1987-1990 w/#2686 head will swap freely amongst themselves. You may be able to swap outside of this range, but I haven't confirmed.

1991-1995 #w/7120 head - swap freely.

1996-1999 w/#0630 head - swap freely.

2000-2001 w/#0331 head - swap freely.

The #7120 manifold should replace the exhaust on the #0630 head, but this is a one-way swap - the primaries on the #0630 manifold are smaller (as are the ports in the head,) and the later manifold will not fully cover the earlier ports.

The #0331 manifold is a special case, and will only swap with itself (this is because it has the two "pre-cats" in it, and you'll get a persistent DTC if you eliminate them.

Chances of swapping between various models gets smaller - if you have a more specific question, feel free to ask (I haven't finished assimilating all of the data to hand yet.) However, information given is opinion based on Hollander Interchange (a source I have learned to consider "definitive") and reports from the field.

Originally Posted by hankthetank

Don't forget about coefficient of linear expansion....cast iron moves .00000655" for every degree F. So...let's say a 30" long iron head x delta 133 x alpha .0000065 = 0.0259 Basically your cylinder head can grow in length about .026" from 77F to 210F. Food for thought.

Originally Posted by 5-90

I haven't - that's why the manifold screws loosen over time, and why those bowl-shaped washers are in place on the screws (although I do still want to experiment with putting true Belleville washers in place. Methinks the spring tension will help them work better, instead of just looking for the elasticity intrinsic to the metal.)

But that doesn't have much to do with swapping parts, and the rigidity inbuilt into the system is a greater factor than the thermal expansion. (Relative motion due to vibration is an order of magnitude or two greater than the expansion due to delta-T.)

Originally Posted by Culprite

this got real technical real quick...thanks guys

Originally Posted by ZINGGG

http://www.ineedparts.com/index.php?...oduct_id=15343

Get it and don't look back. Also take a look at your motor mounts while you're in there. That's the #1 reason the manifold cracks

Originally Posted by BHARP

So Im doing the swap on my 91 XJ and Im wondering can i use the factory manifolds off the LS in this swap or what headers should i use that will fit on between the motor and the unibody rails?