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All the talk about FI lately has me thinking I have a parts jeep with a 4.2 and would like to rebuild it. SO I was thinking a 4.0 head swap (91 -95 head) and I should be able to get all the FI parts form the same donor jeep right? I've done some searching and found some good info but was wondering if any one has done this (and there results) any info / inputs / suggestions / comments would be great
because I know very little about FI and would need to learn more. Thanks
 
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My understanding is that you want to use a 94 or later engine. The 94 is what jeep bases it's Mopar FI setup on...the only difference is that the intake is modified to work with the 4.2 head. But if your going to get a 4.0 head then you will be ok. Just make sure you get all of the parts...including the exhaust manifold, dist, elect fuel pump and all wiring. Your biggest problem is going to be the crank sensor which is normally mounted on the tranny bellhousing. Your best bet is to buy the Mopar harmonic balancer that they use for the Mopar kit. You then mount the CPS on the front timming cover next to the harmonic balancer.

When it comes down to $$ vs time....the Mopar setup is actually cheaper unless you get a doner jeep real cheap. A lot depends on how much your time is worth. One factor in favor of your way is that the 4.0 head alone offers substantial inprovements over the 4.2....and if you find an HO head, even more (apx 15 HP more).

Or you can do what I am going to do....find a wrecked police Chevy Caprice with the 350 and swap the engine and auto into my CJ.
 

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I've just finished swaping a '98 head onto my '80 block and I put 2001 manifolds on. If you use a post '95 head, you will have to use the newer manifolds because of the mounting holes. Vice versa on the '91-95 heads. I used the injectors and ECU from a '94 and the MOPAR harmonic ballancer. I like the results that I got from it, and I am just working out the bugs on my fuel delivery system. Motor has plenty of geddy up, even turning '35's w/ 3.31 gears!
 
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Hummm, it is a nice mod...I am thinking about doing this mod to my 1989 YJ but i am wondering about the gain of power i may get...I have read on different website that the head swap is about 40/50 HP more and i found people saying that MPI swap would give around 20/30 HP...So, it would be a 60/80HP gain???, is the stock 258 can handle that (cranckshaft, rod bearing....)
I have found a 1994 Chero, do you think it is a good donor car to take EVERYTHING from or should i wait and try to find a 1991/1994 YJ 4.0HO ???
Thanx a lot for your help...
 
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