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4.2L to 4.0 swap, CJ7

4.2L to 4.0 swap, CJ7
J

jsledder

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Location
SD
Vehicle(s)
1983 Jeep CJ7. 4.2L straight six, 5 speed manual.
First post... I have a '87 CJ7 with an engine that knocks like there's a huge rock in the oil pan after it gets warmed up (has been doing this for 2 years but it still runs?) I was going to pull it out and rebuild it, but came across a 4.0L out of a mid 90's cherokee and plan on swapping that out. The problem... the guy did not keep the computer or any of the wiring, all I have is the intake with the throttle body and injectors, the CDI and distributor are still there as well.

Does anyone know if I can swap the intake from my AMC 258 i6 / 4.2l and put on a new carb or simply put a carb in place of the throttle body on the donor intake? Don't really feel like going through the hassle of sourcing a computer and all the wiring (as nice as EFI would be, time is of the essence here).

Thanks in advance, I'm sure I'll have more questions.
 
I believe you can bolt it up without to much fuss, others will let you know for sure


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Yes you can either bolt a carburator to the 4.0 intake with an adapter or bolt the AMC 258 i6 / 4.2l intake to the 4.0. If if the 4.0 has the high port head you have to be careful how you get it lined up. You will need the 2 piece intake/exhaust manifolds. The only carburetor adapter that I've found is from Clifford engineering. There quality sucks lately but the only one that makes the adapter. One could be made easily enough if you had the tools.

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One other thing. Your 4.0 may not have a place for a mechanical fuel pump and will need an electric one.

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are you sure its a rod knocking and not a bad valve as the noise only comes once it warms up
 
Thanks all! I'll look for a carburator, adapter and fuel pump.

The knocking sure sounds deep in the engine, could be a valve?? It leaks oil like crazy too so it's time to do something with it, traded a new set of ATV tires for this 4.0L that was supposedly rebuild about 30k miles ago before the vehicle was wrecked.
 
It probably spun the #6 rod bearing. It happens a lot with the AMC 258 i6 / 4.2l . I would source the wiring and computer and use the efi. There a ton of Cherokees in the scrap yards to get what you need. There was a member on here selling what you need to make it work.
 
Last edited:
mtnwhlr said:
It probably spun the #6 rod bearing. It happens a lot with the AMC 258 i6 / 4.2l . I would source the wiring and computer and use the efi. There a ton of Cherokees in the scrap yards to get what you need. There was a member on here selling what you need to make it work.
Click to expand...

xx2
 
jsledder said:
First post... I have a '87 CJ7 with an engine that knocks like there's a huge rock in the oil pan after it gets warmed up (has been doing this for 2 years but it still runs?) I was going to pull it out and rebuild it, but came across a 4.0L out of a mid 90's cherokee and plan on swapping that out. The problem... the guy did not keep the computer or any of the wiring, all I have is the intake with the throttle body and injectors, the CDI and distributor are still there as well.

Does anyone know if I can swap the intake from my AMC 258 i6 / 4.2l and put on a new carb or simply put a carb in place of the throttle body on the donor intake? Don't really feel like going through the hassle of sourcing a computer and all the wiring (as nice as EFI would be, time is of the essence here).

Thanks in advance, I'm sure I'll have more questions.
Click to expand...


I would not use the 4.0 distributor without the computer because you will not get full timing. You need to run the older distributor. You can install the AMC 258 i6 / 4.2l intake in the 4.0 head but it takes some modifying to make it work since the 4.0 head ports are a little higher up. It is pretty easy to do as many of us have with the 4.0 head swap.
 
I suppose I am going to need an electric fuel pump as well? Will that require different lines back to the tank? I'm beginning to think I should have just overhauled the AMC 258 i6 / 4.2l .
 
I used the Carter P4070 electric fuel pump. 4-6psi. About $40 from ebay. Noisy as hell but works good for me. I've had it for several years with no problems. I still keep a spare just in case. Should work with your old lines. Just put as close to the tank as possible.

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You will like the 4.0 im going to turn mine into a stroker motor next year. I would fuel inject it if you can get all the electronics.
 
I would really like to keep the EFI, finding all the electronics could be tough, especially since I don't know what is needed to plug into where to make everything work. This is not necessarily my daily driver, but it is my snow plow rig and it looks like we have about 2-3 weeks before I'm going to need it. I'll get a hold of the previous owner of the engine and find out which model this came out of for sure and work on finding a harness and computer and whatever else.
 
Some sort of an update... I checked out the local "U Pull it" yard (3 hours away) and they have 5 or 6 '97-'00 Cherokee's with the 4.0 sitting there so one of these next warm days I'm going to go and start pulling wiring harnesses and ECM's and whatever else I might need. Anyone that's ever done this, could you give some advice...

1. I'm picturing needing everything from the key switch (mine is bad anyway) to the battery cables basically, how far off am I? Fuse box, relay box, entire harness, all the sensors I can grab.
2. Half tempted to swap out to an automatic Transmission as well, I've got the 5 speed manual right now and had planned on changing the clutch while I had it apart, but an automatic sounds so much nicer, now we are talking steering column, Transmission , driveline, cross member..???

Their prices are stupid cheap, so I figure I just as well go big or go home.... After researching the cost to convert it to a carb setup, I feel it's a much better choice to try and get the EFI functional.
 
Thanks Gert!! Looks like some time killing material there for sure.
 
jsledder said:
Thanks Gert!! Looks like some time killing material there for sure.
Click to expand...



Ya you and caveman have me a bit jealous I wanna build a stroker fuel injection 4.6


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gert said:
Ya you and caveman have me a bit jealous I wanna build a stroker fuel injection 4.6


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Click to expand...
It still wouldn't be as hot as that 360 you already have. Just lighter.

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