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Unread 07-21-2007, 03:50 PM   #1
jclark85CJ7
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Q on Performance Carb for 4.2l, 258 CJ

I need some help. I'm doing an engine pull on my 85 CJ7 4.2L, 258 CI 6cyl and will be swaping with the same powerplant. I know there are a ton of options for performance carbs, but have limited knowledge on them. I'm looking for some advice on Performance Carbs for this Jeep, emissions, not an issue, no inspection in my state, just an all around great carberator that performs well and is very reliable, I've rebuilt the original and still doesn't work right. Any Ideas would be great! Thanks

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Unread 07-21-2007, 04:03 PM   #2
SuB8HaVeN
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If I were you, I would take the 258 I6 and put a 4.0L HO head on it. You could also polish and slightly port the head and build up the valvetrain. You could also install a more aggresive cam. Then, I would put a header on it (various brands) and then get the Clifford 4bbl converter intake manifold. I know some people complained about dumping too much gas on their 258 I6 with a 4bbl carburetor, but I'm sure it would be a different story with a built 4.0L HO head. Maybe someone can fill me in on that one...
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1961 Willys 4x4 Wagon L-226 I6 T90 (restoration also in progress)
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Unread 07-21-2007, 05:04 PM   #3
Bard
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Really depends on your budget. I almost swapped to a 4.0, then picked up a great running 258 and stayed with it. I went with a Weber 34 and it works great, even with what I use my Jeep for, mild to hardcore wheelin, rocks (which surprised me) and everyday driving. I had a 32/36 which wasn't great and what I read on the 38 wasn't in my specs for my setup. I have research the MC2100 which appears to be great as well and budget friendly. So those are the 2 options I will throw your way.
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85' CJ7 Laredo, 383 GM, Turbo 350, NP 203. SOA, 2" frame lift, 34" TSL swampers, Dana 30 open, AMC 20 w/ detroit locker, 4:10's, 1 Piece Mosers, 35" boggers to abuse when needed.
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Unread 07-21-2007, 06:38 PM   #4
tarheel
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hey jclark... i know alot of people on this forum will disagree about the carter carbs but i am one of the ones that really likes them. They are just really touchy when you rebuild them. I have 0ne on my 86 cj that i bought out of Illinios and when i got it here to louisiana it would not run. Rebuilt the the carb and everything. Had a friend that is older that worked for the dodge dealership during the time that they used this carb alot on different vehicles. If ya can find some one who knows how to work on them to tune them just right it is a great carb. I get about 18 mpg on mine and i run 31's on it and it is a daily driver. That is just my opion though.
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Unread 07-21-2007, 07:06 PM   #5
jclark85CJ7
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Quote:
Originally Posted by SuB8HaVeN
If I were you, I would take the 258 I6 and put a 4.0L HO head on it. You could also polish and slightly port the head and build up the valvetrain. You could also install a more aggresive cam. Then, I would put a header on it (various brands) and then get the Clifford 4bbl converter intake manifold. I know some people complained about dumping too much gas on their 258 I6 with a 4bbl carburetor, but I'm sure it would be a different story with a built 4.0L HO head. Maybe someone can fill me in on that one...
Thanks, I considered putting in a 4.0 FI like I used to have in my 94 wrangler, but I'm on a budget and I'm really unsure on wiring harness, tranny compatability etc. Also, the jeep is absolutely an 85 Cherry Laredo even w/ factory a/c (not working @ present but the engine is shot, lots of blowback, bad compression. I also want to keep it original (as possible) w/ the 258, just want a better carb that will take the reliability up. Not a daily driver, just a toy / project. but still don't want it to strand me on the 2hr drive to the beach. I figure I can drop less into motor and a little more into carb and get the kind of p[erformance I'm looking for. I've got a jeep with a perfect body and a bad motor, front susp / steering, and the rear end looks like oatmeal when you open the pumpkin.

What do you think? and thanks for the help in the 1st place

Josh
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Unread 07-21-2007, 07:08 PM   #6
jclark85CJ7
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Quote:
Originally Posted by Bard
Really depends on your budget. I almost swapped to a 4.0, then picked up a great running 258 and stayed with it. I went with a Weber 34 and it works great, even with what I use my Jeep for, mild to hardcore wheelin, rocks (which surprised me) and everyday driving. I had a 32/36 which wasn't great and what I read on the 38 wasn't in my specs for my setup. I have research the MC2100 which appears to be great as well and budget friendly. So those are the 2 options I will throw your way.
Thye weber is where I'm leaning, anyone know of some good priced places on the internet?
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Unread 07-21-2007, 07:47 PM   #7
gosupes
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Quote:
Originally Posted by SuB8HaVeN
I know some people complained about dumping too much gas on their 258 I6 with a 4bbl carburetor, but I'm sure it would be a different story with a built 4.0L HO head. Maybe someone can fill me in on that one...
That's what I have, no complaints. Only about 15MPG with no overdrive though.
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1986 CJ7, 4.2 w/4.0 head, TFI-HEI hybrid ignition, Clifford manifold w/Holley 390 w/cold air intake, OBA, 4.5" lift, Woody CV shaft and Tattons in front, 4.10 gears - lunchbox in front, Truetrac in the back, twin-sticked, blower upgrade for running topless, trying to keep it simple.

It's just a Jeep, and if you don't wheel it once in a while, it's not even that.
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Unread 07-21-2007, 08:30 PM   #8
SuB8HaVeN
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I believe Quadratec.com still has the 34/34 Weber for $299. I jumped on that a while back and installed that and did the nutter bypass shortly after and it's like a new Jeep now. Installing the Weber gave it so much more power, fuel economy, and it runs way smoother. Plus the kit that they come in is entirely end to end so you don't have to go searching for adapter plates for the intake manifold, etc.
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Unread 07-23-2007, 07:58 PM   #9
jclark85CJ7
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Quote:
Originally Posted by SuB8HaVeN
I believe Quadratec.com still has the 34/34 Weber for $299. I jumped on that a while back and installed that and did the nutter bypass shortly after and it's like a new Jeep now. Installing the Weber gave it so much more power, fuel economy, and it runs way smoother. Plus the kit that they come in is entirely end to end so you don't have to go searching for adapter plates for the intake manifold, etc.
Pardon my ignorance, but what exactly is a Nutter bypass
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Unread 07-23-2007, 08:08 PM   #10
Bard
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Do a google search for details. Cutting the computer, wiring and all other bs out of the way. I got my Weber from weber direct or carbs direct I think, somewhere in NY.
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85' CJ7 Laredo, 383 GM, Turbo 350, NP 203. SOA, 2" frame lift, 34" TSL swampers, Dana 30 open, AMC 20 w/ detroit locker, 4:10's, 1 Piece Mosers, 35" boggers to abuse when needed.
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