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Unread 03-01-2013, 04:13 PM   #1
LowBudget87YJ
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1987 YJ Wrangler 
 
Join Date: Feb 2013
Location: Lucia, NC
Posts: 37
another 4.0L head swap ?

Hey guys/gals im new to the forum but not wrenching and fab. work. Question is and if it has been answered before I apologize. I'm swapping a 4.0L head and basically everything from the head up onto my 4.2L to gain the benefits of the 4L head and fuel injection, and i'm not sure as to what to do about the distributor. I have done the juice box upgrade already on the 258 but will this setup work? Beside the obvious wiring to the new harness and ECM is there anything else that I'm missing? Finally if this setup will not work what do I need to use so that it will work?

Thanks for y'alls help and if you must flame then feel free your not going to hurt my feelings none. I'm surrounded by 200 other infantrymen on a daily bases y'all cant be no worse

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Unread 03-02-2013, 03:31 PM   #2
LowBudget87YJ
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1987 YJ Wrangler 
 
Join Date: Feb 2013
Location: Lucia, NC
Posts: 37
Also which pushrods to use since they are different length's?
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Unread 03-02-2013, 09:59 PM   #3
jamesbland123
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1987 YJ Wrangler 
 
Join Date: Jan 2012
Location: Newbury Park, CA
Posts: 62
I did this same upgrade. If I remember correctly I used the 4.2 pushrods. There is also some work you need to do on the heads such as close up 2 or so coolant channels, but I can't exactly remember.

Are you talking about MPFI? If you are going this route there is a lot you need to do besides wiring. I did the MPFI as well and its a pretty big undertaking if that's what you are talking about besides the head.
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Unread 03-03-2013, 01:34 AM   #4
LowBudget87YJ
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1987 YJ Wrangler 
 
Join Date: Feb 2013
Location: Lucia, NC
Posts: 37
im using the factory FI from a 91 xj. i gone through forum and write up after write up and these where the only to things that i could not find an answer yet. thats for your help buddy if i cant get or find a definite answer then im probably just pick up a adjustable pushrod to measure the correct length. still not sure about the dissy and ignition system
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Unread 03-03-2013, 05:41 AM   #5
blown50
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1987 YJ Wrangler 
 
Join Date: Apr 2007
Location: MS, MS.
Posts: 134
Either or pushrods will work, both my 258 and 4.0 had the same length pushrods. You will have to set lifter preload, I used Ford 5.0 rocker shims under mine to get proper preload! Can't help you on the wiring as I'm still carbureted.
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Unread 03-03-2013, 11:59 PM   #6
LowBudget87YJ
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1987 YJ Wrangler 
 
Join Date: Feb 2013
Location: Lucia, NC
Posts: 37
really 5.0 shims thats awesome ive got a set of those sitting in my box of dont throw away cause you never know parts. thanks for the help on that question now if i can find out if my exsisting ignition system will work ill be good to go.
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