1991 H.O. stock exhaust

[HoboBones]

I've been patching my exhaust system for years and it finally snapped between the muffler inlet and front exhaust pipe. I'm going to go ahead and replace everything from the manifold (which is cracked) to the tail pipe. My rig is my daily driver and completely stock. I'm on a tight budget, completely new to exhaust systems,  and wanted to reach out for some guidance. It would be nice to allow the engine to breath a bit better but am not aiming for performance gains. I'm in good standing with a local shop whose willing to install the parts when ready.

 

Exhaust Manifold - I was able to find just a straight up stock replacement but was reading about the "flex pipe" recommendation. Do they make any stock manifolds with the flex pipe or do I need to get one? Do I need to find a manifold that is H.O. specific?

 

Front exhaust pipe (# 5200 4996) - I'm having trouble finding this stock , does anyone have a link or reference?

 

Muffler - Walker Exhaust Quiet-Flow 21690 2.25" inlet/outlet

 

Catalytic Converter - Any recommendations? I was surprised how expensive these are.

 

Tailpipe - Stock

 

Other - Will I need new hangers, supports, or brackets?

 

Would it be a better to just get a new stock manifold and have the shop replace the rest of my system?

 

Really appreciate any advice or resources. 

[Gojira94]

I've spent some time recently going through options myself, though I'm doing a blend of OE and custom parts. Here's what I found during that search:

 

https://www.rockauto.com/en/moreinfo.php?pk=8626088&cc=1181775&pt=5860&jsn=857

Manifold with the flexible sections between 1-2, 5-6, less prone to cracking from what I've read here and there. It fits 91-92 MJ, 91-99 XJ, 91-96 YJ, 97-99 TJ, 93-98 ZJ.

 

https://www.rockauto.com/en/moreinfo.php?pk=135706&cc=1181775&pt=10038&jsn=853

Walker front pipe for MJs with cat (square flange)

 

Muffler- many choices for 2.25" offset in/ center out in a 21-ish inch length, whatever suits you

 

https://www.rockauto.com/en/moreinfo.php?pk=129238&cc=1181775&pt=5808&jsn=867

Walker cat assembly. CARB compliant cats are over $600. What state are you in?

 

Tailpipe- Walker has both 6' and 7' box pipes

 

Rubber insulators are available for either/ both. Stock hangers are fine if they're intact and you're essentially doing OE replacement parts

 

[gogmorgo]

If you look at parts for a ‘93 XJ they’re a bit cheaper. The catalytic converter in particular. The only difference is the downpipe to cat connection is a slip fit instead of the flange and gasket. Its what I’ve got on my ‘91 longbed. Factory manifold still I think, whatever was on the used engine I swapped in a while back, ‘93 XJ downpipe, cat, and muffler, and a Walker MJ tailpipe. I got the pipe sections through a local parts store a while back, and the muffler and cat off rockauto. Likely would have got the pipe sections off rockauto as well but shipping long things is murder. I also didn’t bother trying to extract my old O2 sensor and just bought another. 

 

The other option would be to talk to a local exhaust shop, get a custom pipe bent if you can’t track down something pre-bent. You’ll almost definitely end up with something better quality too. 

[HoboBones]

Holy smokes this was super helpful, cleared up a lot of small details for me. I just needed to see a freakin accurate diagram. This is pretty much what I had in mind. I was looking into the cherry bomb mufflers mentioned on here a while back. Will most likely see what the shop can offer and just throw in the cheapest thing for now.

 

On 5/4/2013 at 9:02 PM, onlyinajeep726 said:

Cherry Bomb Pro muffler.  Running one on my '96 XJ 4.0L HO and it sounds good without the ricer sound, but still grumbles enough to make her sound good.

 

Here's the link on Amazon.com: <http://www.amazon.com/gp/product/B0018GQRD4/ref=oh_details_o05_s00_i00?ie=UTF8&psc=1>

 

For the insulators and all that extra/misc hardware, is there some sort of kit available?

 

Really appreciate the info

[gogmorgo]

The Cherry Bomb parts are not great. Thin metal, rusts out quick. Not that the Walker pipe I used would last much longer. But I got a stainless cat and muffler. I can dig up the part numbers for everything when I get home in an hour or so. 
If you look at the hanger/isolator listing on Rockauto for the MJ the Walker ones will show you which rubber isolators you need and where they go. You need two of the ones at the muffler end of the tailpipe, and one for the front, assuming you’re using a pre-bent pipe. An exhaust shop may have other ideas. 
Otherwise, exhaust manifold bolts are available as a kit. You’ll want a new intake/exhaust gasket if you’re pulling your manifold.

Theres a compressed metal donut gasket at the manifold to downpipe connection. 
The downpipe to cat flange connection takes a flat gasket. If you go with the ‘93 pipe with the slip fit all you need is a 2-1/4” exhaust clamp there. 
Then there’s an additional 2-1/4” clamp on either end of the muffler. 

[pizzaman09]

I have a Flowmaster Flow FX muffler on my truck and love it.  It's quite on the road but makes a phenomenal sound at idle.  Appears to be quite high quality.

[DesertRat1991]

The Walker parts were well made, but I seem to recall several members have tried to source Walker MJ parts through various vendors only to find they are hopelessly backordered.  It's possible that Walker has finally made another run but parts were scarce about a year ago.  Maybe call around a bit before you get your hopes up. 

[gogmorgo]

Yeah. I got my Walker tailpipes through a small but well-established chain. They only had one of each in their warehouse at the time. Initially they ordered the long bed pipe by mistake when I’d wanted one for my short bed, so I hung onto it. That said, Rockauto does show inventory of both Walker tailpipes. The cost of shipping long pipes is a little absurd for me, but someone south of the 49th parallel might have it a little easier, I wouldn’t know.

For my ‘91 4.0 I went with the Walker 22502 “quiet flow” muffler and 15773 cat. Picked the muffler mostly because it wa stainless and fairly cheap. It’s got a nice little rumble at idle, and you can definitely hear it in the cab, but it’s not so loud as to feel like I’m upsetting the neighbours. I lost over 12 decibels at highway cruising speed according to the questionable app on my phone compared to the Flowmaster. Now I can hear my Hakkas grinding the pavement down instead just the exhaust droning away. 

 

54488 downpipe, and the 47605 tailpipe for my longbed. Short bed tailpipe would be 46701.

It all slid together perfectly three with three 2-1/4” clamps, two 35750 insulators, and one 35719. I think you could get away with using three 35719 insulators, they’re half the price of the 35750, but I didn’t take the chance it wouldn’t work for the $14 it would’ve saved. If your insulators are still in decent shape there’s no real need to replace them however. There’s also another little rubber bit on the crossmember. Rockauto has a couple options, listed as “cushions” in the trans mount section. I didn’t bother replacing mine.

I also reused the donut gasket between manifold and downpipe. Just couldn’t make the replacement I got fit. Manifold gasket and hardware should be readily available from your preferred parts supplier. I ended up with Dorman bolts but Felpro also makes the set. 

 

 

[Gojira94]

Here's the setup I'm building - not exactly cheap with a $200 muffler but the rest is inexpensive, easily had, and adapted. What I'm doing works for 91-92 HO applications, while 87-90 4.0 would be a different story. 87-90 Manifold and downpipe options would be OE, but cutting off the converter flange would open up options for more custom 2.25" cat and muffler choices between downpipe and tailpipe as well.

 

Mine:

 

91-99 HO manifold (already have one on the 93 YJ drivetrain I acquired, manifold is practically new)

 

Walker 55277 96-99 XJ downpipe (largest inner diameter of all of them at 2.5" but it does neck down closer to 2.25" in a couple of spots and back up to 2.5" and no big dent behind the inlet flange)

Magnaflow 94006 cat (15.75" overall length, 3.75" thick, 6.5" wide, 2.5" ID, rated for 6000lbs, 2-way ceramic honeycomb, 47-state OBD1 approved)

 

Flowmaster 52571 (70 series, 2.5" offset inlet, center outlet, 28" overall length, 5" H x 10" W x 22" L body). I wanted something deep and quiet with minimal flow resistance.

 

Walker 46701 86-92 2.8/2.5/4.0 tailpipe until I can have one duplicated in 2.5" at a local shop. Napa is tightly partnered with Walker so short wheelbase pipes are not hard to get. Long bed part is 47605, 86-92 2.8/2.5/4.0, availability somewhat less.

 

Couple short pieces of 2.5" OD pipe and a 2.5" OD to 2.25" ID reducer in the meantime. I can size the joins at the downpipe to converter and converter to muffler so the overall distance between the downpipe and tailpipe remains the same without cutting either, or moving the tailpipe hangers before I have the 2.5" tailpipe made.

 

I ripped out the glass matting under the carpet on the passenger side  when I pulled the interior. To shield the passenger floor from converter heat I've found a neat resource in any boneyard, anywhere. I look for full-size GM trucks and pull one of their heat shields. Stick your head under one and you'll see what I'm talking about. You can trim them to whatever size and shape you want (they're huge). Use tin shears, plus eye and breathing protection, as there's fiberglass fill in them. Then roll and crimp the cut edges back together. Mounting one under the floor isn't rocket science, GM shields have at least 2-3 mounting tabs you can re-use. You can grab one very close to the size and shape you'd want anyway.