Thinking of doing the 4.0L HO Engine Change on my CJ7, Good? Pro / Cons? - JeepForum.com
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Unread 09-10-2012, 08:16 PM   #1
CJBRENT
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Thinking of doing the 4.0L HO Engine Change on my CJ7, Good? Pro / Cons?

I'm half way done of restoring my son's 1984 CJ7, 5-Speed, its all original equipment on it.

I'm thinking of doing the 1990-1992 4.0L High Output engine swap.

Who has done one on here? What's the Pro's / Con's of doing this? I just want something really reliable then the motor it has now.

Maybe Auto, or Stick, I have NOT made up my mind yet.

I know there is conversion kits out there, what is the middle grade one....

Any help would be great! Thanks Brent!

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Unread 09-10-2012, 09:35 PM   #2
kschitoskey
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4.0 Swap

Brent, you are doing the right step - research. There are literally thousands of posts addressing this popular swap. I did mine in 99 and it is still running great. Motor mounts are almost bolt on - one bolt hole has to be enlarged. Use the 4.0 flywheel, as it has the notches for the crankshaft position sensor. You can modify your stock bellhousing, or Novac will do it for you. I bought a Hesco harness - plug and play for the most part. I also bought their fuel supply lines and bent up a fuel lines myself. I had a custom fuel tank made with 2 pickups - one for the stock CJ pickup so I could use my stock fuel gauge. The second for an in-tank fuel pump. I used my stock radiator. My 4.0 came out of a cherokee so it had the offset fan. I removed the fan and went with a contour fan, which works great. For intake I bought a "Rock It" 4.0 high flow intake, painted to match the block / body. Clearly I'm missing a lot of details but as you can see it was a great move for me. I doubled my horsepower / torque and kept it emissions legal.

Good luck and post pictures!
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Unread 09-10-2012, 09:44 PM   #3
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Brent,

I am just starting the swap. Although original 258 is still running OK I am tired of hard starts and cranky behavior in the mornings and the rich running when I am up in the mountains. I did a huge amount of research into my options and could only see going two ways - either a 4.0 MPI or a TBI Chevy V6 or V8. Since your Jeep is also an 85, it probably had the same 258 and T5 combo. After looking at all the options I bought a wrecked 91 Cherokee for $600 that had the 4.0 and AX-15 5 speed. This gives me the stronger transmission with a hydraulic clutch and eliminates the need to deal with the crank sensor kit, as it will still be in the AX-15 bell housing.

Look at the Hesco website and read their tech info, as they have a lot of good stuff on the MPI conversion. I will be starting a build thread shortly so look to see how my fumbling goes :-)
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Unread 09-10-2012, 11:30 PM   #4
CJBRENT
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See, awesome! This is WHY I'm asking questions of this swap I want to do. I'm tired of the cranky 258 to, had the carb rebuilt 3 times! Just put way way to much money into it. By now I could of put the 4.0L H.O. in my Jeep, with either a Automatic, or the AX15 trans. I do want to do this right, no short cuts or hack jobs. The Jeep has a PERFECT, I mean PERFECT body on it (NO RUST ANYWHERE), just needs interior and do something with the 258 (which im tired of). This Jeep is for my 12 year old son, and I've had it for 6+ years already, so I want it SAFE first of all, and of course really reliable for him to drive. But still looking for more ideas to, I kinda want to go with a nice 2 or 3 row aluminum radiator, electric fan, get the fuel tank done right, fuel lines, etc.

I know it's extra money, but In my option, its well worth it in the long run.

Again, so far thank you for all the help and advice, I'm pretty sure I'll do the swap, but just want my cage rattled a little more to move forward on this project. I think while I do this, I'll send it off to the paint shop to get a nice and shinny paint job on it.
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Unread 09-11-2012, 12:15 AM   #5
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This is one of the easiest mechanical swaps for a CJ but the electrics and plumbing are daunting to the weekend mechanic, so have a good look at what is involved before taking the plunge.

You do not necessarily need a new gearbox for the swap but this would be a good time to think about something stronger.
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Unread 09-11-2012, 04:41 AM   #6
RWise
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The only thing I like the 4.2 better on is bottom end torque, it's a bit less with the 4.0, but that can be regained by stroking the 4.0,,,,
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Unread 02-15-2013, 07:44 PM   #7
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I know this thread is a bit on the older side at this point, but I have a question here, as I am looking into the 4.0L HO swap as well. My 78 CJ7 has the 258 in it currently (non running since the day I bought it) coupled to an NV4500/Dana 300 Combo. When I swap in the 4.0L HO, will I need to get a new bell housing to mate it up with the transmission/t-case combo? I've seen a myriad of info on the swap, all good info BTW, but nothing dealing with a non-standard transmission already in place.

Note: when I bought the CJ, it already had the 258/NV4500/Dana 300 combo in place, so I plan on reusing as much of the drive line as possible to keep costs down a bit)
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Unread 02-15-2013, 08:03 PM   #8
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Your existing bellhousing can stay. The 258 and 4.0 share the same pattern, so if a bell fits a 258 it also fits the 4.0.

You will want to have it modified to accept a crank position sensor if you don't run the CPS off of the harmonic balancer via one of the Hesco relocate kits.
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Unread 02-15-2013, 08:09 PM   #9
SgtJensen
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Quote:
Originally Posted by CSP View Post
Your existing bellhousing can stay. The 258 and 4.0 share the same pattern, so if a bell fits a 258 it also fits the 4.0.

You will want to have it modified to accept a crank position sensor if you don't run the CPS off of the harmonic balancer via one of the Hesco relocate kits.
How involved is the modification for the CPS? Would that be something better left to a machine shop?
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Unread 02-15-2013, 08:18 PM   #10
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It can be done if you have the correct dimensions for the hole and for the hole's placement. Novak Adapter's website might have some information on this.
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Unread 02-15-2013, 08:35 PM   #11
SgtJensen
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Thanks for the info. I've still got quite a bit of time to do my research, as my CJ is in TX, and I'm in Japan for a few years...
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Unread 02-15-2013, 08:51 PM   #12
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My two cents worth...if you don't want to swap motors, but want to upgrade the 258, look at a junkyard 4.0 head and fuel injection swap. Very straightforward and can retain your stock cj tcase, tranny, and driveshafts.

Find a running 4.0 and take the whole engine including starter and flywheel, entire underhood wiring harmed, ECM, pdc, and the sensors.

I did this to mine for under $400 and I love. Best mod I've ever done. Starts right up, no warmup, smooth. It's Cadillac!
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Unread 02-15-2013, 09:02 PM   #13
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Quote:
Originally Posted by aggiejon View Post
My two cents worth...if you don't want to swap motors, but want to upgrade the 258, look at a junkyard 4.0 head and fuel injection swap. Very straightforward and can retain your stock cj tcase, tranny, and driveshafts.

Find a running 4.0 and take the whole engine including starter and flywheel, entire underhood wiring harmed, ECM, pdc, and the sensors.

I did this to mine for under $400 and I love. Best mod I've ever done. Starts right up, no warmup, smooth. It's Cadillac!
I've heard about doing this, but I'm not sure about the status of the motor as it sits right now, I'm pretty sure it would need a total tear down and rebuild. That and it was missing a few of the front end components.

My plan is to swap in the 4.0L HO complete with EFI system, then do a budget stroker kit using what internals are still good, from the 258, plus a cam upgrade.
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Unread 02-16-2013, 08:49 AM   #14
aggiejon
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Sarge, you mentioned living in Tx. Where at? I like your plan for the stroked 4.0. I considered it with mine, but needed to get it back on the road and I knew the bottom end of the 258 was solid and sound, so I let that dog lie.

I am no expert on the efi by any stretch, but if you get into it and have questions, give me a shout. I took the wiring diagram and Pinout diagram for the donor harness and removed everything that I couldn't use for my jeep. Cherokees have lots more systems than cjs. But I did gain several relay circuits in the PDC. And the harness became much lighter quick.

Largest word of caution...I cobbled mine together from parts that I bought cheap from several sources, such as a complete siezed 4.0 motor from a 2001. That yielded a very desirable intake design. However, the throttle body was different from the 93 Engine harness, so it was swapped for a 93. Many of the sensors from 92-2001 look the same on the business end, but the plugs changed quite a bit. I still have a box full of sensors that were either from the 01 motor or picked at the junkyard. Take home message, get on Craigslist and buy a wrecked and running jeep w a 4.0 and strip it. Part it out or else roll it across the scales for $11/cwt.
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Unread 02-16-2013, 09:34 AM   #15
ymurf
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I did this swap last winter and also used the AX15 5 speed.Here is a link to my thread.I love the fuel injected 4.0.
http://www.jeepforum.com/forum/f8/of...hread-1307046/
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