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Unread 09-16-2011, 03:21 PM   #1
superj
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4.2 exhaust question

hey guys, i have a 4.2 head and am thinking of using 99 exhaust manifolds. can i do this? i have searched for about 30 minutes now trying different terms and cannot find a thread saying yes or no.

i have a 4.0 head also but need to get it to ndt to check for cracks before i install. i visual'd it and it looked fine but i don't want to install and find something wrong and not have my vehicle to take the kids to practices and such.


also, still no one makes an adapter to put a carb on that 99+ intake manifold? i got that too

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Unread 09-16-2011, 05:42 PM   #2
superj
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you guys think i should post this in the cj section? i had forgotten about how a lot of people on here don't know too much about the 4.2

i know its only been two hours
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Unread 09-16-2011, 06:10 PM   #3
gbeltran
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No, it won't work. 4.2 stuff is unique to the 4.2 on the exhaust manifold.
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Unread 09-16-2011, 06:44 PM   #4
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This may or may not help, but in a previous career I spent a lot of time analyzing lots of things. So I tend to look for cause and effect relationships.

I bought my first Jeep about a year ago, an 89 YJ with a 4.2L motor. Had to redo the exhaust system. One of the glitches was a broken manifold stud at the rearmost position. Reading up on here and another forum, the 4.2L motors have a reputation (on the YJs) for either cracking the rear part of the exhaust manifold or shearing that bolt. When I started reassembling with fresh gaskets etc., it became obvious that the manifold hole did not match the stud position closely enough.

I elongated the hole in the exhaust manifold by about .10 inch with a die grinder. I also found one other bolt or stud with questionable alignment near the middle of the head and relieved it slightly. I don't expect to have a repeat of the broken stud problem nor a cracked manifold. New gaskets on both manifolds and all ran well with no leaks.
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Unread 09-16-2011, 07:00 PM   #5
gbeltran
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Why are you trying to put a carb on the 99 intake? You would have to make your own adapter. If you want to keep the carb with the 4.0 head you can use your current intake. I think you might have to grind the mounting flange in a couple spots but it will work.
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Unread 09-16-2011, 08:05 PM   #6
superj
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Bummer on the exhaust manifolds, I was hoping they fit.

On the intake manifold, I got the whole head (well, engine) but no harness but no ecu so while waiting to collect parts, I figured I would move to a better flowing intake.
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Unread 09-16-2011, 10:07 PM   #7
444
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The 4.0 intake is designed for dry flow with the injectors at the head. It is not suited at all to mounting a carb on. If you want a good flowing carb intake, but one of the aftermarket 4.2 4bbl intakes.
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Unread 09-17-2011, 04:09 AM   #8
superj
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I have lOoked at them and if I could find one for a cost I like, I would buy one. I just have a hard time shelling out 2-300 for an intake
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Unread 09-17-2011, 06:41 AM   #9
wanabejeeper
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I'm pretty sure the 4.0 HO head will take the 4.0 throttle body intake which can use a carb.
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Unread 09-17-2011, 08:36 AM   #10
superj
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I only know one guy on here with a 99+ intake and running a carb. He made the adapter himself
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