AMC 258 I6 performance mods -
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Unread 05-12-2008, 09:37 PM   #1
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Join Date: May 2008
Location: Grand Rapids
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AMC 258 I6 performance mods

I just recently put in a brand new AMC 258 inline 6 into my 1987 YJ. It's great, but I would like to make some modifications in order to gain more hp and increase mpg. Any suggestions? The most obvious seems to get a performance carburetor or new exhaust system. Right now, it's a gas hog and often hesitates upon acceleration. Thanks.

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Unread 05-12-2008, 11:31 PM   #2
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1993 YJ Wrangler 
Join Date: Apr 2008
Location: michigan
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I am in the process of doing the same install in my 89. I agree with the performance carb, personally I went with the weber. Swap the distributor for an HEI, it throws more spark. Or you could scrap the carb, do a 4.0 head conversion and go fuel injected. The 258 heads flow for crap anyway.

Good Luck,
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Unread 05-18-2008, 09:33 AM   #3
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1987 YJ Wrangler 
Join Date: Aug 2006
Location: grafton ohio
Posts: 3,286
Yep, 4.0 head conversion and efi kit, and run synthetics in the whole drivetrain. Jaccobs omnipack helps with power and mpg as well.
1987 wrangler, 258 I-6, 5-speed.
2007 liberty sport 4X4, automatic
2009 ford ranger 4x4 FX4 OFF/ROAD, 5-speed
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