Exhaust Help

[54bobby]

so I pulled the exhaust pipe off today to replace it do to a hole. when trying to fit the ne one on, I discover that the system has been frankinsteined together. one of the po's must have replaced the cat with an after market so it looks like they cut about 8 inches off the front pipe, clamped a generic cat on and used a collar to fit it to the muffler. I have never done exhaust work before so my question is, how do I connect the rear of the cat to the new muffler and the rear of the muffler to the tail pipe? cat to exhaust has a four bolt flange so that I get. do the pipes just slip inside one another then tightened down with new hardware? 

[Oddmodman]

:needpics:

[Eagle]

On the stock system, the catalytic converter bolts to the exhaust pipe (down pipe) with a 4-bolt flange, so it sounds like you're good on that part. All other connections are female/male slip fittings. The catalytic converter has a moderately long output put that leaves the cat as a 2-1/2" and reduces to a 2-1/4" OD. The muffler inlet is 2-1/4" ID, so the muffler slips over the cat. The muffler outlet is also 2-1/4" ID, and the tailpipe is 2-1/4" OD, so the tailpipe slips into the muffler outlet.

 

If you need to make up length, the parts houses have short 2-1/4 ID x 2-1/4 OD adapters you can use to make up the difference.

[54bobby]

cool, so I just really clamp the pipes together with the U clamps to hold them in place?

On the stock system, the catalytic converter bolts to the exhaust pipe (down pipe) with a 4-bolt flange, so it sounds like you're good on that part. All other connections are female/male slip fittings. The catalytic converter has a moderately long output put that leaves the cat as a 2-1/2" and reduces to a 2-1/4" OD. The muffler inlet is 2-1/4" ID, so the muffler slips over the cat. The muffler outlet is also 2-1/4" ID, and the tailpipe is 2-1/4" OD, so the tailpipe slips into the muffler outlet.

 

If you need to make up length, the parts houses have short 2-1/4 ID x 2-1/4 OD adapters you can use to make up the difference.

[Oddmodman]

Well, guess he can do it without pics. Lol.  :cheers:

[Eagle]

If a picture is worth a thousand words, what did I just do? Maybe 100 or 150 pixels?

[Eagle]

cool, so I just really clamp the pipes together with the U clamps to hold them in place?

That's all you need.-- two muffler clamps. (Three if you have to insert an adapter to make up length.)

[Keyav8r]

Depending on where you bought the parts, there's a possibility you may have to shorten the tailpipe at the muffler in order to get the hangers to line up. I hope you got new rubber isolators/hangers as the old ones on my truck had to be cut off. New ones make the system assembly easier. If necessary, you can get a tailpipe expander from the parts store (Advance Auto, Auto Zone, O'Reilly's, etc - free rental but you put up a deposit) to expand the pipe end and make a joint if you have to cut the pipe.

[54bobby]

went with all walker products so I should b ok.

[dinghyboy]

only suggestion I'll add is to place it all together before you go clamping anything. The PO on mine had cobbled a system together and it rubbed the frame over the rear axle. I went with Walker products also and ended up buying a new cat to replace the existing one to get the system to line up properly. Without it the hangers wouldn't line up properly.

 

Good Luck

 

Gavin 

[54bobby]

so, just to be clear, I will NOT need to weld anything, correct? just fit the pipes together and clamp em down. should I start at the manifold and piece it together as I move rewards or assemble then install?

[Eagle]

Manifold? I thought you were just replacing the muffler and tailpipe.

 

Wherever you start, work from the front toward the rear. Heed dinghyboy's advice to line things up before clamping. But ... unless you need to replace the front exhaust (down) pipe, you won't be touching the manifold. The front pipe ends in a 4-bolt flage, and there's no way that can be misaligned, so you can bolt up a new catalytic converter (if you're replacing that" and sock it down. The cat flange connection uses 5/16" bolts, IIRC, and it takes a gasket. Don't forget the gasket. If you're buying the parts from AutoZone, I was just there half an hour ago and their listing for a 2001 Cherokee is incorrect. They show a 3-bolt gasket for the front pipe to catalytic converter, and it should be a 4-bolt gasket -- just like the Comanches.

[54bobby]

i'm doing from the manifold all the way back. are the U clamps strong enough to hold tight w/o welding?

[54bobby]

Manifold? I thought you were just replacing the muffler and tailpipe.

 

Wherever you start, work from the front toward the rear. Heed dinghyboy's advice to line things up before clamping. But ... unless you need to replace the front exhaust (down) pipe, you won't be touching the manifold. The front pipe ends in a 4-bolt flage, and there's no way that can be misaligned, so you can bolt up a new catalytic converter (if you're replacing that" and sock it down. The cat flange connection uses 5/16" bolts, IIRC, and it takes a gasket. Don't forget the gasket. If you're buying the parts from AutoZone, I was just there half an hour ago and their listing for a 2001 Cherokee is incorrect. They show a 3-bolt gasket for the front pipe to catalytic converter, and it should be a 4-bolt gasket -- just like the Comanches.

 

I need to buy the 5/16 bolts and nuts to connect the cat to the down pipe. how long should the be?

Manifold? I thought you were just replacing the muffler and tailpipe.

 

Wherever you start, work from the front toward the rear. Heed dinghyboy's advice to line things up before clamping. But ... unless you need to replace the front exhaust (down) pipe, you won't be touching the manifold. The front pipe ends in a 4-bolt flage, and there's no way that can be misaligned, so you can bolt up a new catalytic converter (if you're replacing that" and sock it down. The cat flange connection uses 5/16" bolts, IIRC, and it takes a gasket. Don't forget the gasket. If you're buying the parts from AutoZone, I was just there half an hour ago and their listing for a 2001 Cherokee is incorrect. They show a 3-bolt gasket for the front pipe to catalytic converter, and it should be a 4-bolt gasket -- just like the Comanches.

[Eagle]

Mate, unless you absolutely need a new front pipe, do NOT try to change it. You WILL break or strip at least one of the studs where the pipe flange bolts to the exhaust manifold, and then you'll have no choice other than to drill out the broken stubs and hope you don't trash the manifold in the process.

 

IIRC, the four bolts at the cat flange need to be two different lengths. I think two are 1" and two and either 1-1/4" or 1-1/2".

 

Just measure what you have.

 

Yes, the muffler clamps are strong enough without welding. That's what the factory used. I've been using them for over 50 years -- I've never welded an exhaust system in my life.

[54bobby]

well, I already got the front pipe off w/o breaking any studs. what is iirc? also I don't have the old flange bolts cause the old system was w/o that flange. just clamps at the mating of all the junctions in the system. the old cat was an generac one that was just clamped on. 

[Keyav8r]

iirc is an acronym for "if I remember correctly". Don't forget to get a new silver colored "doughnut" gasket for the manifold/downpipe joint. Also, get the better, silver colored casket for the downpipe/cat flange. I think Fel-Pro makes it. Use "never seize" on the manifold studs with new nuts, preferably stainless steel

I just did this, including the manifold, on my 88. Definitely assemble everything from front to back before tightening the manifold bolts or installing the clamps. The downpipe/cat bolts can be tightened as this joint can't be adjusted by turning. the top side of the cat has a heat shield, be sure it's installed with the shield side up. Make sure the tailpipe is lined up with the hangers and not too far forward or back. If you are using a "stock" muffler it will have (iirc) a center inlet and an offset outlet. I can' remember whether the offset outle should be toward the frame rail or toward the drive shaft. Maybe someone else can jump in here and clarify that. If not, I'll look under mine when I get back next and send you a PM. Or, just assemble it one way (without the clamps) and then try iy the other way if it doesn't look/fit right. My truck has a formed clearance in the frame to clear the pipe. If the pipe is not positioned correctly it will hit and rub on the frame. Also, make sure the straight section on the back end of the pipe (the part that sticks out behind the wheel) has a little tilt down toward the end of the pipe so that any exhaust condensation will run out.

After everything is in place and properly lined up, tighten the manifold bolts and clamps, then go back and re-check everything.

[54bobby]

thanks man, i'll keep you posted.

iirc is an acronym for "if I remember correctly". Don't forget to get a new silver colored "doughnut" gasket for the manifold/downpipe joint. Also, get the better, silver colored casket for the downpipe/cat flange. I think Fel-Pro makes it. Use "never seize" on the manifold studs with new nuts, preferably stainless steel
I just did this, including the manifold, on my 88. Definitely assemble everything from front to back before tightening the manifold bolts or installing the clamps. The downpipe/cat bolts can be tightened as this joint can't be adjusted by turning. the top side of the cat has a heat shield, be sure it's installed with the shield side up. Make sure the tailpipe is lined up with the hangers and not too far forward or back. If you are using a "stock" muffler it will have (iirc) a center inlet and an offset outlet. I can' remember whether the offset outle should be toward the frame rail or toward the drive shaft. Maybe someone else can jump in here and clarify that. If not, I'll look under mine when I get back next and send you a PM. Or, just assemble it one way (without the clamps) and then try iy the other way if it doesn't look/fit right. My truck has a formed clearance in the frame to clear the pipe. If the pipe is not positioned correctly it will hit and rub on the frame. Also, make sure the straight section on the back end of the pipe (the part that sticks out behind the wheel) has a little tilt down toward the end of the pipe so that any exhaust condensation will run out.
After everything is in place and properly lined up, tighten the manifold bolts and clamps, then go back and re-check everything.

[54bobby]

so, my new hardware is here and the front pipe has an o2 sensor port where as the old pipe doesn't. the present o2 sensor is in the manifold. part#'s are correct. I do have a new mani that i'm going to install at a future timeand it has a plug in the sensor port. question is, can I install my new sensor into the pipe and leave the old one in the exhaust manifold as a plug till i do the manifold job. if all this makes sense. also. I have the flange gasket for the pipe to the cat and I also bought another piece (packing)is what rock auto calls it. it is listed in the exhaust hardware dropdown for my 87 2.5. it is a silver metal ring. does it go into the joint where the cat bolts up to the exhaust pipe? I can't find a diagram of it in the Haynes manual.

[54bobby]

job complete. truck sounds great. both pipes, cat and muffler.