YJ 4.2 Exhaust question - Page 2 - JeepForum.com
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post #16 of 25 Old 08-25-2011, 12:15 AM Thread Starter
digs71
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Well if you look at the video that was posted this is EXACTLY what they did. It's a set of headman headers. Just like wanabejeeper posted. They do (2) 3 into 1 out from the heads. The headers typically run around $260. And as far as power goes, my jeep may not be a 350 chevy. But it does JUST fine on power, and I have NO complaints!

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post #17 of 25 Old 08-25-2011, 12:20 AM
Tom95YJ
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My stepbrother had a magnaflow cat, Air pulse tube, and flowmaster 40 with new mandrel bent tailpipe put on his 89 at a local exhaust shop for $340 out the door fully welded with new hangers IIRC it was 2.25in and he did 2.5" out

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post #18 of 25 Old 08-25-2011, 09:01 AM
wanabejeeper
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Quote:
Originally Posted by digs71 View Post
Well if you look at the video that was posted this is EXACTLY what they did. It's a set of headman headers. Just like wanabejeeper posted. They do (2) 3 into 1 out from the heads. The headers typically run around $260. And as far as power goes, my jeep may not be a 350 chevy. But it does JUST fine on power, and I have NO complaints!
I've read that you should have a crossover between the duals just behind the header... helps with scavaging exhaust from cylinder and pulling in fuel/air.

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Originally Posted by Anticanman View Post
It goes in that barrel you wheel out to the street once a week.

My build thread http://www.jeepforum.com/forum/f12/n...thread-867043/
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post #19 of 25 Old 08-25-2011, 06:28 PM Thread Starter
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Flowmaster claims that the best way to do the crossover is the "X" over the "H". They said that this would give you much better results. As far as cost goes, my shop did this from the head back for only 250 out the door. So not bad at all!
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post #20 of 25 Old 08-27-2011, 05:06 PM
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hey guys. within the next few days i think im going to be ordering a flowmaster exhaust. my question though, is that when you look up exhausts on their site, they 1) dont show my '90 YJ, they show '91-present, and 2) they dont show the exhaust i want for even a 91. So i guess my question is, are they interchangable? could i buy a '95 exhaust and put it on my '90???
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post #21 of 25 Old 08-27-2011, 08:04 PM
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Quote:
Originally Posted by Wrangler2012 View Post
hey guys. within the next few days i think im going to be ordering a flowmaster exhaust. my question though, is that when you look up exhausts on their site, they 1) dont show my '90 YJ, they show '91-present, and 2) they dont show the exhaust i want for even a 91. So i guess my question is, are they interchangable? could i buy a '95 exhaust and put it on my '90???

You can order the catback for another year upto 95 it shouls work. I would consider a custom exhaust shop , they can usually get you a catback fully welded up with new bent pipes and muffler of your choice for the same price or less than a companys catback package

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post #22 of 25 Old 08-28-2011, 06:17 AM Thread Starter
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IF you order a "cat-back" I wouldn't order a 95 year model if you have a 90 year. The reason is because they are different motors. In 90 it was still the 4.2l, and in 91 they switched to 4.0.

As far as the exhaust it's self they are interchangeable. It all comes down to what size pipe you are going to use. You can get all different size in and out. Just need to know what size you want/need.

AND it is MUCH cheaper to have someone weld the combo up then purchasing it on your own. Like I said mine was only 250 and that was to do all new pipes from the heads back which is so much more than you get with just a cat back system (and much cheaper).
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post #23 of 25 Old 08-28-2011, 10:45 AM
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I just put a dynomax cat back on my 1990 that has a 4.2. It was supposed to be used on a 91 and up, the only difference is pipe diameter. the 91 and up has 2.5 inch instead of 2.25 inch diameter. any ways it fit great with no problems and cost $95 because dynomax was running a big sale on them.
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post #24 of 25 Old 09-05-2011, 07:47 AM
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its all about flow, a quick moving exhaust will help pull in fuel/air during valve overlap... Dont know for sure if there is a real benifit with a dual in an inline but what the designers try to do is link the cylinders up with respect to the cylinder firing so that scavanging takes place. Some dual setups use a crossover pipe connecting the two to elp with this...

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Quote:
Originally Posted by Anticanman View Post
It goes in that barrel you wheel out to the street once a week.

My build thread http://www.jeepforum.com/forum/f12/n...thread-867043/
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post #25 of 25 Old 09-05-2011, 12:11 PM
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Quote:
Originally Posted by TheNewbie View Post
How can you do "true duals" on an in line motor?
My dad recently purchased two jeeps for us manly because my son wanted one.

1. 1988 YJ Laredo 4.2L AT
2. 1994 YJ SE 4.0L MT

The 1988 has a true dual exhaust using a split Pacesetter Header which now for my purposes has to be completely redone due to E-Testing where I live.

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Everyone has an opinion & this is just mine sorry if it offends anyone.

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1988 Black YJ 4.2L AT
1994 Red YJ 4.0L MT

Last edited by mcgyver210; 09-26-2011 at 07:55 PM.
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