Y-pipe to single pipe setup - JeepForum.com
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post #1 of 11 Old 06-02-2020, 06:21 AM Thread Starter
anotherheep
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Y-pipe to single pipe setup

Morning! So I've started a rebuild on my 4.0 and been looking at exhaust manifold replacements. Most of what I'm seeing online dump into a single pipe right off the manifold as opposed to the stock setup I have right now which dump into the y-pipe. I'm wondering if anybody makes a replacement pipe that will replace the y-pipe setup to a single pipe setup....or do i need to have something custome bent? I'm sure this has been discussed, but I'm not having much luck finding anything about it. Thanks!

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post #2 of 11 Old 06-02-2020, 06:52 AM
mudpack
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RockAuto has two-piece exhaust manifolds that allow you to use the stock Y-pipe.

two 2004 WJ 4.7 Quadra-Drive Limiteds
one 2012 WK2 SRT8
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post #3 of 11 Old 06-02-2020, 07:25 AM Thread Starter
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I've seen the original style manifolds for sale, but have also heard of the cracking issues with them. Mine aren't actually even broke, but figured I would do some preventative as long as I have everything out. Am I jumping the gun with even replacing them? I know motor mounts going bad is a contributor to this and plan on putting new ones in.
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post #4 of 11 Old 06-02-2020, 11:32 AM
coldspit47
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Your factory emissions package is what determines the y-pipe configuration. You have a y-pipe, which means you should have 50 state emissions (including CA), which has 2 pre-cats, one on each branch of the y-pipe, each with its own O2 sensors upstream (on the manifold) and downstream (below the pre-cat). As I've said before, tampering with or removing factory emissions equipment or equivalent is a Federal no-no. You *can* likely get away with it, but why bother?

Just about every aftermarket exhaust company has a configuration to fit the 4.0 - 50 state or Federal. Just look for one that says 50 state compliant (unless you currently live in CA or NY, in which case you'll need a CARB compliant model). Even AAP has two-piece versions. If/when I get around to needing to replace my exhaust manifolds, I'm probably just going to pull the trigger on a set of Thorleys. They're only about $150 more than the manifold set AAP has (w/o shipping) and about $100 less than RA. If it were my build, I'd replace everything within failure range while the engine was out. You can replace the manifolds while the engine is back in your Jeep but it's easier pulled.

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post #5 of 11 Old 06-02-2020, 04:02 PM Thread Starter
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I'm not trying to tamper with any emissions being that the thing would most likely run like crap if I did. I don't have two upstream cats on mine. I have a pipe going to each exhaust manifold that then go into one pipe, then to the cat. The exhaust manifolds I'm looking at are a one piece that need to go into one pipe, not a y-pipe. I'm just trying to figure out if someone makes the pipe that will work for the new single outlet manifold or if I need to have one made.
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post #6 of 11 Old 06-02-2020, 04:14 PM Thread Starter
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Maybe I'm not being technically correct calling it a y-pipe for the setup I have (4.0), but it seems like one to me.
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post #7 of 11 Old 06-02-2020, 05:20 PM
coldspit47
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Quote:
Originally Posted by anotherheep View Post
I'm not trying to tamper with any emissions being that the thing would most likely run like crap if I did. I don't have two upstream cats on mine. I have a pipe going to each exhaust manifold that then go into one pipe, then to the cat. The exhaust manifolds I'm looking at are a one piece that need to go into one pipe, not a y-pipe. I'm just trying to figure out if someone makes the pipe that will work for the new single outlet manifold or if I need to have one made.
What year is your WJ?

You must be lucky enough to have Federal emissions. I didn't realize any factory WJ exhaust manifolds were one piece 6>1, learn something new every day! Thought they got rid of that with the ZJs. Might have luck looking at XJ/ZJ pipes, since they used the 6>1 design rather than 6>2>1. Intermediate pipes, I believe is what they're called, or I see Walker calls it a front exhaust pipe (55277 for XJ). For the sake of ease it might be worth it to look at a different manifold, so you can just bolt it right in without buying lots of other pieces/parts. Or can just buy the flange for the intermediate pipe and have one made.

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post #8 of 11 Old 06-02-2020, 06:34 PM Thread Starter
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Originally Posted by coldspit47 View Post
What year is your WJ?

You must be lucky enough to have Federal emissions. I didn't realize any factory WJ exhaust manifolds were one piece 6>1, learn something new every day! Thought they got rid of that with the ZJs. Might have luck looking at XJ/ZJ pipes, since they used the 6>1 design rather than 6>2>1. Intermediate pipes, I believe is what they're called, or I see Walker calls it a front exhaust pipe (55277 for XJ). For the sake of ease it might be worth it to look at a different manifold, so you can just bolt it right in without buying lots of other pieces/parts. Or can just buy the flange for the intermediate pipe and have one made.
Its a '99. My STOCK is indeed a 6>2>1 setup. I'm not sure if they ever came 6>1 or not (too new to Jeep still). The biggest reason I'm interested in the aftermarket 6>1 is the price which is cheaper even with replacing the intermediate pipe. I also like the look and the fact that its a single pipe.
I hear you on looking into the XJ/ZJ pipes, but trying to get anything to jive online between models is not working so great. I'll probably just call a shop and see if they know the bend required, or worst case I load it on the trailer and haul it down to them to hook it up.

Thanks for the feedback, Cheers
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post #9 of 11 Old 06-03-2020, 01:28 PM
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The factory manifold(s) are a two piece. Many aftermarket "headers" come with a collector that routes all 6 pipes into a single attachment point. But i have not seen one that would bolt right up. Usually if you go this route, the pipe has to be cut and a new flange added....by a muffler shop. Any good muffler shop should fly through a job like this. Remove your manifolds and cut the pipe off. Then install the manifold/header and drive it to the shop to finish the job. Thats what I do. Kinda noisy... but thats how i like it anyway...Usually the aftermarket manifold/header is worth the extra effort, because it helps the 4.0L breath a little better, and they shouldn't crack like the factory setup.

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post #10 of 11 Old 06-04-2020, 08:49 AM Thread Starter
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Originally Posted by Bigrigr View Post
The factory manifold(s) are a two piece. Many aftermarket "headers" come with a collector that routes all 6 pipes into a single attachment point. But i have not seen one that would bolt right up. Usually if you go this route, the pipe has to be cut and a new flange added....by a muffler shop. Any good muffler shop should fly through a job like this. Remove your manifolds and cut the pipe off. Then install the manifold/header and drive it to the shop to finish the job. Thats what I do. Kinda noisy... but thats how i like it anyway...Usually the aftermarket manifold/header is worth the extra effort, because it helps the 4.0L breath a little better, and they shouldn't crack like the factory setup.

Thanks for the reply. I'm a little surprised that somebody who sells these aftermarket manifolds doesn't make a pipe to make the transition smoother. I mean, if I were selling them I would. Liked your idea of driving to the shop with it undone, but my luck would never let me get there without being pulled over and making a big deal out of it...besides the fact I haven't even had a chance to tag the thing yet.
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post #11 of 11 Old 06-05-2020, 08:43 AM
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Quote:
Originally Posted by anotherheep View Post
Thanks for the reply. I'm a little surprised that somebody who sells these aftermarket manifolds doesn't make a pipe to make the transition smoother. I mean, if I were selling them I would. Liked your idea of driving to the shop with it undone, but my luck would never let me get there without being pulled over and making a big deal out of it...besides the fact I haven't even had a chance to tag the thing yet.

Oh, you definitely wouldn't wanna drive it this way without tags and insurance. Ha Ha
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