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Unread 05-19-2010, 08:42 PM   #1
88blkyj
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1988 YJ Wrangler 
 
Join Date: Feb 2010
Location: Florida
Posts: 583
4.2 and 4.0

are same cast iron block?

4.2 used different heads and cam there stroked to a 4.2?

My uncle has a header he is giving me that was used on his 4.0

pretty sure it would still bolt on?

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Unread 05-19-2010, 09:08 PM   #2
yellow2kgt
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1990 YJ Wrangler 
 
Join Date: Jun 2005
Location: Fishersville,Va
Posts: 1,011
Actually the ports are different on the 4.0 head so the header will not work. Swap in a 4.0 head and it will.

Also, the 4.0 block has a larger bore then the 4.2.
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1990 Jeep YJ 4.2
Howell EFI, BDS 3.5" lift, M.O.R.E 5/8" Boomerang shackles, 1" Daystar BL, 1" JKS MML, TFI, Crager soft 8s w 35" Dunlop Mud Rovers, Ford 8.8, 4.88s, Dana 30 E-Locker, Terra Flex SYE, Tom Woods CV shaft, Warn M8000.
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Unread 05-19-2010, 10:00 PM   #3
88blkyj
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1988 YJ Wrangler 
 
Join Date: Feb 2010
Location: Florida
Posts: 583
dangit. That just ruined my day... but was what I was expecting =[

thank you.
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Unread 05-20-2010, 09:36 PM   #4
88blkyj
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1988 YJ Wrangler 
 
Join Date: Feb 2010
Location: Florida
Posts: 583
Is there anyone to make these fit beside swapping heads?
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Unread 05-21-2010, 06:21 AM   #5
dodger889
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1989 YJ Wrangler 
 
Join Date: Jan 2009
Location: mi
Posts: 4,161
Buy the ones that fit they are only about $100 for the right ones.
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A 89 yj with a 4.0 aw4 sye out of an 92xj. Now the hard part is done time to get it up in the air just a bit. Working on 8.8 with 3.73 and lsd for the rear. and new D30 hp with 3.73 .
For those who have not figured this out I'm old school but can handle the new too.
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Originally Posted by bigsquat View Post
im just cheap, and cheap makes you creative.
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