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Unread 10-01-2011, 04:39 PM   #1
drive78CJ7
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78 CJ 4.0L Swap

Hello,

Do to my jeeps upsetting performance on the trail last weekend I have decided to upgrade from my Carter 1 Barrel fed 258 I6 to a 4.0L FI Motor. I bought a 1995 Grand Cherokee with a 4.0L in it for a donor vehicle. I have read many forums on how to do the swap but figured I would talk about my build and see if any one has any input.

What I am planning on taking for the Cherokee

- Motor (of coarse)
- Wire Harness(s?)
- Exhaust Manifold
- 02 Sensor
- Fuel Pump?

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Unread 10-03-2011, 11:51 AM   #2
drive78CJ7
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Well I got my Donar Car Below and will hopefully have the motor out this or next week.. I am undecided to whether I should Just clean up the motor and drop it in or if I should rebuild it... two questions is what parts if any are interchangable from the 4.2L to the 4.0L? And does anyone have any recomendations on what to do with the motor before I stuff her in. I just put a new timing chain and distributor in my 4.2L I dont think the distributor will work because it has vacumm advance.

Any info would be great thank you.
jeep-donar.jpg  
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Unread 10-03-2011, 07:00 PM   #3
OlivergreenCJ7
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You might want to look into running the tranny from the 4.0 as well. You should be able to upgrade to a D300 to keep your passenger side diffs. SAVE all wiring. It might also be useful to get the wiring diagram from the donor vehicle and your CJ. I helped a buddy put a 4.0 from an XJ into his YJ and we just took the whole drivetrain. Worked out very well, but the wiring was very overwhelming. Cool build. keep us posted.
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Unread 10-04-2011, 10:35 AM   #4
drive78CJ7
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I would like to keep a standard shift in my CJ... I have a T-150 now but thinking of going to a T-18 My head is spinning a little from all the reading I have done on Mating a 4.0L to a t-18 and a Dana.

Anyway.. I think I am going to tackle the Motor first... I will be trailering the Cherokee out to my shop hopfully in the am. Should be pulling it out this week.
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Unread 10-04-2011, 03:46 PM   #5
addicted2dunes
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You'll have to get your bellhousing machined for the CPS if you want to run your trans. I did a 4.0L swap in my CJ, if you need any help, just ask!
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Unread 10-04-2011, 03:48 PM   #6
addicted2dunes
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Wiring is not too bad, five wire hook up. The BIGGEST problem you may encounter, since it's a ZJ, is the SKIM module, built in security system, make sure you get the SKIM box too if it has it. Or you can get a ECM from a YJ or XJ, they don't have SKIM and they can have manual trans.
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Unread 10-04-2011, 03:53 PM   #7
addicted2dunes
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Quote:
Originally Posted by drive78CJ7 View Post
Well I got my Donar Car Below and will hopefully have the motor out this or next week.. I am undecided to whether I should Just clean up the motor and drop it in or if I should rebuild it... two questions is what parts if any are interchangable from the 4.2L to the 4.0L? And does anyone have any recomendations on what to do with the motor before I stuff her in. I just put a new timing chain and distributor in my 4.2L I dont think the distributor will work because it has vacumm advance.
How many miles are on the engine? 4.0L are stout motors. When I did mine I changed the freeze plugs, timing cover seal, rear main seal, valve cover gasket, and oil pan gasket just to make sure it wouldn't leak any oil. I did the freeze plugs just to be safe and it's cake work to do when the motor is out. No parts are really interchangeable between the 4.0 and the 4.2..... granted you can take a 4.0 head and put it on a 4.2 for the fuel injection and you can take the 4.2 crank and use it in the 4.0 to make a 4.6 stroker. You can not run the CJ distributor with the 4.0 engine, the computer gets a lot of info and adjusts the timing as needed through that computer controlled distributor on the 4.0
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Unread 10-04-2011, 03:58 PM   #8
addicted2dunes
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And one more time..... most people run an external fuel pump for the 4.0 in the CJ's. Now you can modify your fuel tank to accept the ZJ fuel pump if you really wanted. I used the complete ZJ fuel tank, fuel lines, everything in mine, granted I have a Scrambler and the length on everything and tank fitment worked perfect with a Scrambler, I don't think it'd work on a CJ7 though.
Also, what kind of auto tranny is in it? If it's an AW4 that is a stout auto trans, if it is a 42RE, like mine, they are week but upgradeable. Novak Adapters sells a clocking ring/ spacer for the AW4 and AX15 trans to adapt to the Dana 300, all it is is a 7/8" spacer, works awesome..... Advanced Adapters also sells it too, but I think they are a bunch of *******s.
If you want the best manual bolt in trans try to find an AX15 trans, they are strong as hell and have all the revisions for the CPS.
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1981 CJ8 - http://www.jeepforum.com/forum/f8/project-krawln8-81-cj8-1276742/
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Unread 10-05-2011, 07:46 AM   #9
drive78CJ7
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The truck shows 142K Miles on the odometer.. I think it may be leaking some oil through the Valve seals because it smokes alittle when I start it up cold. I think that I will not do a full rebuild but maybe do the seals and gaskets that way I hopefully will not have an oil leak (seep) problem. But besides that It runns pretty well in the Cherokee.
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Unread 10-05-2011, 07:48 AM   #10
drive78CJ7
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Quote:
Originally Posted by addicted2dunes View Post
And one more time..... most people run an external fuel pump for the 4.0 in the CJ's. Now you can modify your fuel tank to accept the ZJ fuel pump if you really wanted. I used the complete ZJ fuel tank, fuel lines, everything in mine, granted I have a Scrambler and the length on everything and tank fitment worked perfect with a Scrambler, I don't think it'd work on a CJ7 though.
Also, what kind of auto tranny is in it? If it's an AW4 that is a stout auto trans, if it is a 42RE, like mine, they are week but upgradeable. Novak Adapters sells a clocking ring/ spacer for the AW4 and AX15 trans to adapt to the Dana 300, all it is is a 7/8" spacer, works awesome..... Advanced Adapters also sells it too, but I think they are a bunch of *******s.
If you want the best manual bolt in trans try to find an AX15 trans, they are strong as hell and have all the revisions for the CPS.


Will the AX15 trans mate to my Dana 20?
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Unread 10-05-2011, 08:04 AM   #11
drive78CJ7
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also.. What do I have to do to my fuel tank to accept the Cherokees fuel pump?
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Unread 10-05-2011, 08:06 AM   #12
drive78CJ7
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Quote:
Originally Posted by addicted2dunes View Post
Wiring is not too bad, five wire hook up. The BIGGEST problem you may encounter, since it's a ZJ, is the SKIM module, built in security system, make sure you get the SKIM box too if it has it. Or you can get a ECM from a YJ or XJ, they don't have SKIM and they can have manual trans.
Can I use an ECM from any year YJ or XJ? And If I do that I do not have to look for a manual specific one? If I go that route will that eliminate the need for the SKIM Mod.? Also what does it look like? ha
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Unread 10-05-2011, 09:03 AM   #13
addicted2dunes
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Quote:
Originally Posted by drive78CJ7 View Post
Will the AX15 trans mate to my Dana 20?
Yes, but that is pricey......

AX15, 42RE, AW4 to Dana 20 - $528 - http://www.novak-adapt.com/catalog/kit_152.htm

If you can find a Dana 300 t-case:
AX15, 42RE, AW4 to Dana 300 - $136 - http://www.novak-adapt.com/catalog/kit_153.htm
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1981 CJ8 - http://www.jeepforum.com/forum/f8/project-krawln8-81-cj8-1276742/
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Unread 10-05-2011, 09:08 AM   #14
addicted2dunes
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Quote:
Originally Posted by drive78CJ7 View Post
also.. What do I have to do to my fuel tank to accept the Cherokees fuel pump?
I've seen people that attach the ZJ fuel pump to the factory CJ sending unit. Not too sure how this is done seeing that I haven't done it. You'll also need to have a return line running back from your fuel rail to the tank.

CJOffroad.com used to be the ultimate 4.0 swap forum, it hasn't been around in about a year or so though. If you go to waybacktimemachine.com you can search the archives. Here is a 4.0 sticky that used to be on the site, lot's of info. - http://web.archive.org/web/20060219171357/http://www.cjoffroad.com/forums/topic.asp?TOPIC_ID=1097

Edit: Here is some info from CJOffroad.com -

1. How do you install the in tank fuel pump in a 20 gal. plastic CJ tank?
answer: hose clamp pump to bottom of CJ's pickup tube. Cut tube to fit first. Drill 2 1/4" hole in top of sender. Install 2 1/4" rubber gommets. Splice wire on fuel pump and tripple tripple shink tube. Thread up through grommets. Install in tank. You want the pump to where it just touches the bottom or is just slightly above the bottom. Thread huge plastic retaining nut back on and seal the entire top of sender. I used GE silicon II but if I know of a fuel proof product, I'd use that. I'm told that silicon doesn't hold up to fuel but I just don't want the smell to get past the grommets.
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1981 CJ8 - http://www.jeepforum.com/forum/f8/project-krawln8-81-cj8-1276742/
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Unread 10-05-2011, 09:14 AM   #15
addicted2dunes
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Quote:
Originally Posted by drive78CJ7 View Post
Can I use an ECM from any year YJ or XJ? And If I do that I do not have to look for a manual specific one? If I go that route will that eliminate the need for the SKIM Mod.? Also what does it look like? ha
Any year that had a fuel injected 4.0. Don't get a Renix computer..... that system won't work. If you decide to use the auto computer you will have to ground out the NSS wire on the computer if you are running a manual trans. If you get a non SKIM computer it will eliminate that system. The SKIM module is a black box with a red connector, I think it was behind the glove box somewhere in the ZJ if I remember correctly. It is about 4"x3"x1.5" or so.

Do you know wiring? One BIG thing that will help ypu a lot is getting a FSM (Full Service Manual), a factory manual, it shows everything, all the wiring, color coding, etc.
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1981 CJ8 - http://www.jeepforum.com/forum/f8/project-krawln8-81-cj8-1276742/
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