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Unread 02-01-2014, 03:13 PM   #1
89yjislanderr
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1989 YJ Wrangler 
 
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4 bbl or v8

hey folks. as my profile states, i have a 4.2 5speed. lookin to get more power. my first thought was a 4 barrel carb, but after buying one and a new 4 barrel manifold, ill have spent the same, if not more, than i wouldve on a used v8. any thouhts?

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Unread 02-01-2014, 04:43 PM   #2
Que89YJ
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There isn't enough air flow for a 4bl. Do the nutter bypass.
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Unread 02-01-2014, 04:46 PM   #3
superj
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I have a 4 barrel and will be doing a v8 sometime because the i6 still isn't as fun as I like. I have an auto tranny though
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Unread 02-01-2014, 05:06 PM   #4
YJ4LIFE
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It's tricky deciding which fork in the road to go down. I've stuck wiht the 4.2L and will keep it as long as it lasts and use the money I didn't spend replacing it doing other things for now. You might want to do a 4.0L head. I didn't because my 4.2L head was in good shape but it would have made my EFI swap WAYYYY easier.
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Unread 02-01-2014, 05:06 PM   #5
Que89YJ
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Super, you are running a 4-bl on a 4.2?
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Unread 02-01-2014, 05:39 PM   #6
roadyrob
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a few of us run 4 bbls. I have a holley 390cfm, along with a few other mods. it performs real well for a 6 cyl. OP, you can find deals on the manifold on ebay and craigslist. you need to check prices on a v8 swap, no way you can do it for 8-900.
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Unread 02-01-2014, 06:25 PM   #7
Que89YJ
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Quad 390? I thought the 4-bl would flow way too much gas. I have never heard of a 390 Holley! I love this forum, I learn every time I'm on here .
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Unread 02-01-2014, 07:09 PM   #8
jsawduste
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First to go is the 3.07 gears. Add some gear to the poor thing so it can at least start to stretch it`s legs a bit. It will never run well they way it is geared now.

Darryl, Ron up is St. Helen is running an 82 CJ7 with an offy intake and Edlebrock 4 BL. Played with the jetting and vacuum springs and it runs pretty darn good.
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Unread 03-04-2014, 05:56 PM   #9
1987_yj
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Quote:
Originally Posted by roadyrob
a few of us run 4 bbls. I have a holley 390cfm, along with a few other mods. it performs real well for a 6 cyl. OP, you can find deals on the manifold on ebay and craigslist. you need to check prices on a v8 swap, no way you can do it for 8-900.
I run a Holley 390 on an Offy. I have a dead spot I am trying to overcome. Can you point me in the direction of some threads to help with this? I have changed a wealth of carb parts. I am stuck.

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Unread 03-04-2014, 07:10 PM   #10
roadyrob
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Quote:
Originally Posted by 1987_yj View Post
I run a Holley 390 on an Offy. I have a dead spot I am trying to overcome. Can you point me in the direction of some threads to help with this? I have changed a wealth of carb parts. I am stuck.

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this might help

http://www.junkyardgenius.com/holley/tune01.html
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Unread 03-04-2014, 07:52 PM   #11
superj
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I am running a 450 holley but the 390 is run by a few local guys on aftermarket intakes and they really like them
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Unread 03-07-2014, 01:01 PM   #12
zeus87gn
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Quote:
Originally Posted by 1987_yj View Post
I run a Holley 390 on an Offy. I have a dead spot I am trying to overcome. Can you point me in the direction of some threads to help with this? I have changed a wealth of carb parts. I am stuck.
http://www.holley.com/TechService/Library.asp

Pay attention to the Power Valve section
You may need to change it to a faster one - I had to to overcome my stumble
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Holley Carb thread
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Unread 03-07-2014, 01:03 PM   #13
zeus87gn
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Quote:
Originally Posted by jsawduste View Post
First to go is the 3.07 gears. Add some gear to the poor thing so it can at least start to stretch it`s legs a bit. It will never run well they way it is geared now.
^^ This ^^ is the first problem

Then concentrate on your tune and get the ignition fixed up and bypassed
(if it hasn't been done already)
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Unread 03-09-2014, 09:22 AM   #14
1987_yj
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Thanks! I have replaced the power valve with stock size but I will check the vacuum again and compare

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Unread 03-09-2014, 09:36 AM   #15
0III0forlife
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I too run a Holley 390 CFM. After going from the Carter to a Weber, to a MC2150, then getting pissed and putting on an Edelbrock 600, I opted for the Holley.

But it requires some add-ons to perform well...Such as fuel pressure regulator, and some springs on the floats to prevent cutout when climbing a hill. Knock on wood, it has been performing to my liking for over a year now.
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