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Need performance inhancement ideas from 4.2L 258 gurus


 
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Boise_YJ
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Joined: 09 Sep 2007

PostPosted: Mon Oct 01, 2007 4:52 pm    Post subject: Need performance inhancement ideas from 4.2L 258 gurus Reply with quote

Hello,
I was wondering what the most value added upgrades anyone might recommend for the 258 (short of replacement). Hoping for best ideas for the less expensive enhancements....Thanks.
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dadstoys2
Member


Joined: 08 Nov 2005
Location: York, PA

PostPosted: Tue Oct 02, 2007 10:06 pm    Post subject: Reply with quote

Mine runs like a beast. I love it!

Upgrades are:
Nuttered
Webber carb
2 1/2" exhaust with hi-flow cat and 4series flowmaster

Soon I plan to do the 4.0 head swap thats good for up to 40hp more, and I can retain my carb but must use the 4.0 header. Some water jackets must be fuse welder to swap it but its nothing too big.
Gears will help for me since I have the horrible 3.07's
~Rich
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Boise_YJ
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Joined: 09 Sep 2007

PostPosted: Wed Oct 03, 2007 1:36 am    Post subject: 258 upgrades Reply with quote

Thanks Rick..What is "nuttered"????

Dave.
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Code3TJ
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Joined: 01 Jan 2004
Location: Uzbekistan

PostPosted: Wed Oct 03, 2007 9:03 am    Post subject: Reply with quote

http://www.jeephorizons.com/phpbb/viewtopic.php?t=2542&highlight=fuel
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Nothing to see here.
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FARMER
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Joined: 29 May 2007
Location: Benicia Ca.

PostPosted: Thu Oct 04, 2007 7:32 am    Post subject: Reply with quote

If you opt for a 4.0 head, the H.O. used until "89" or the ZJ head (same as the H.O. head ) up till "95" are the better choices. After those years Jeep used a smaller exhaust valve to help the engine come up to operating temp. quicker and reduce the emissions while cold. Another option for more power is an Offenhauser 4 barrel intake manifold.
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