Installing Completely New Exhaust

1990 Jeep 4.0L I need to install new cat, muffler, and exhaust pipe. I am planning on getting a direct fit cat. The direct fit cat I am looking at has a outlet diameter 2 1/4. Inlet side, and outlet side of muffler 2 1/2. Exhaust pipe 2 1/4 inlet, and outlet. So basically a whole new rear exhaust. Anyway will a 2 1/4 pipe fit into a 2 1/2 pipe? I want to use exhaust clamps, so there is no welding required. Will this work?

No, it won't fit correctly. 2 1/4 ID (inside diameter) needs to fit into a 2 1/4 OD (outside diameter). This is different from a 2 1/4 pipe going into a 2 1/2 pipe. Either get the right size or adapters are also available (second choice is not as good, you don't need extra parts to leak or come apart).

10334226 said:

1990 Jeep 4.0L I need to install new cat, muffler, and exhaust pipe. I am planning on getting a direct fit cat. The direct fit cat I am looking at has a outlet diameter 2 1/4. Inlet side, and outlet side of muffler 2 1/2. Exhaust pipe 2 1/4 inlet, and outlet. So basically a whole new rear exhaust. Anyway will a 2 1/4 pipe fit into a 2 1/2 pipe? I want to use exhaust clamps, so there is no welding required. Will this work?

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1/4 inch is too much to clamp away. As long as the outer pipe is the larger, you can just get a sleeve. I haven't looked recently, but it used to be quite easy to find the right sleeves at an auto parts store, in the section where they have little bits of exhaust pipe, adapters, etc. The sleeves have a stepwise cut so that when they are clamped, they seal well, and little tabs at the ends to keep them from slipping too far off the tube or into the muffler. If the larger pipe or muffler goes inside, then you'll need to cut out a section and put in an adapter. These exist as well, but it's not at all convenient, and adds another joint and weak spot to your system.

With this said, I'd suggest you shop around and see if you can get a system with correct sizes all the way around, because although the sleeves will work well enough to make a system legal, etc., you may find that the system is a bit weak, prone to loosening especially if you go off road. Aside from that, a system that necks down from larger to smaller always smacks a bit of shade-tree engineering.

What Matt said... The stock size on the muffler is 2 1/4". Get the right size. Having a 2 1/2" Muffler does little to no good if you choke it back down to 2 1/4. Or find a 2 1/2" Exh pipe.

AH... what muffler are you putting on?

Basically What your saying is I need to order everything with 2 1/4 inlets, and outlets. If I do this they will all slide right into eachother, and I can just use clamps right?

That's it.

Why not order a cat w/exhaust kit? Might save a buck, and it should all fit together.