3blackbirds

Hello all,

I'm trying to figure out this issue for my 1999 Cherokee with 0630 head.

Within the past year:
Stinky Fab Racing Motor mounts.
(I've had M.O.R.E, but they're a bit too stiff for me)

OEM Trans mount
Mandrel bent down pipe with 6" flex joint.

I keep breaking manifolds at the welds every 2 years. I've gone from cheap to APN and Dorman. I'm tired of doing this job. I've just replaced my 4th.

My next move is to put the two piece cast exhaust manifold from the 0331 head, plug the 02 sensors and have a new down pipe made up with a new bung for one 02 sensor. I know I'll need an adapter plate because the 0331 manifold won't cover the 0631 exhaust ports. Yes, a more restrictive manifold but I'm tired of the cracking. I have a 4" lift, so piping will clear the driveshaft.

Is there anything I'm missing or can consider before I put the two piece on? I don't want to spend hundreds on this for an aftermarket two piece right now. I'd like to get this set up and stable before I purchase a nice Borla or Banks etc. down the road.

Thanks in advance

tech

Have you tried a header that is made more for performance some are made thicker and heaver and coated so they don't crack .

3blackbirds

I haven't tried them yet. I've read that they are prone to cracking as well. I'd put a Banks or an aFe, etc on there if it were a sure thing. In my mind, having a two piece will give it more flexibility to move around.

Cummins93

What condition is the exhaust to transmission hanger in? As they wear they will provide zero support for the front half of the exhaust system.

3blackbirds

The hanger is in great shape considering it has 246k miles. The hole isn't distorted and the rubber isn't cracked. The pipe feels solid in that mount. I have a good 1" between the cross member and pipe. The bolts through the trans mount that holds this bracket in are tight.

MECRAM

I installed a BANKS REVOLVER header, wrapped it in thermo tape. WOW what a difference! It now accelerates in 6%+ grades in 4th. Auto equipped. Though within months it developed a major cracks in a couple of at the collector. I initially thought it was from the tape, rust thru. When removed it was evident it wasn't the case. Having new mounts eng & t/c it's not from mounts. 95 XJ with 175k miles with original exhaust. I repaired the cracks and reinstalled. I believe the cracking was caused by or significantly influenced from the original hangers. The rubber had dried to the point it was near solid, when I wiggled the pipe it barely moved and took more effort than it should. At the time I was pleased with the rigidness, though thinking about it, I realized it should have flex from the hangers that easily move. So I and upgrading my exhaust for a few reasons. 1) replace hangers 2) install 10 flex 3) address overheating, possibly, runs hot driving flat and on hills and drops immediately on down grades - thoughts, restriction causing heat build up 4) Turbo install
Hope this helps
Regards,

3blackbirds

I'm going to look into my mount at the trans more closely. There's a bit of work to get that rubber piece out. No one makes it anymore, but you can use the older style with modification.

I think I may add another flex joint behind the oil pan. The current one is after the 90 degree bend inline with the cat just prior to the cross member.

CobraMarty

Cracked headers is not the headers fault. Even the best will crack.
The problem is the long exhaust and the movement. It is like a long lever arm all acting on the header.
We have had good luck with a mounting tab from the crossover pipe to the trans to solid mount the header and crossover pipe to the engine/trans. Now the pivot point is not the header but further back.

Cummins93

To the OP, what motor mounts are you running? I wont use the stock design anymore as it is worthless. I like the rubber ones from rustys. Similar vibration as stock but the engine is locked in.

MECRAM

That's a good idea.

3blackbirds

Do you have a picture or can you point me in the direction of how to do this? I've been looking into mounting the pipe at the cross member differently. My pipe from the cross member back is pretty solid.



Exhaust is a full 2.5" with aftermarket cat, magnaflow muffler and performance-curve tail pipe. It gets tight at the back with a hidden hitch, 3.5" IRO spring and boomerang shackle. It has to sit just right or it'll touch the gas tank shield or leaf spring.