4.0L Swap into 86 CJ-7: Need answers! - JeepForum.com
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post #1 of 7 Old 01-04-2012, 02:10 PM Thread Starter
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1986 CJ7 
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4.0L Swap into 86 CJ-7: Need answers!

So I have an 86 CJ-7 with 4.2 and T-5 that pretty much needs to be
restored, and while I'm at it, I was thinking of doing a 4.0L swap as it
sounds like I'm going to need to rebuild the top end of the engine anyway.

I'm literally disassembling it and rebuilding from the ground up, money isn't
a huge issue but if I could keep it around $1000, I'd be happy cuz I've
already spent a bunch on the body and ill need to spend another couple
grand for the little stuff. Is $1000 even realistic?

My main question is where should I get the 4.0L if I want to convert it to
fuel injection as well? I've heard of some people swapping from an old
Cherokee, but I found a 95 YJ with only 175xxxKm's (108xxx miles) for like $500.

Let me know what you're thinking, it would be nice to get a little discussion
cuz this is my first build so I could use some help.

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post #2 of 7 Old 01-05-2012, 12:50 AM
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I also have a 86 CJ7 and need to swap the motor out. I am at over 191000 miles and the piston slap is getting bad. I have researched everything from a 258, 4.0, Chevy 5.3, 4.3 and I think that the Jeep don't need much more that the 6 cyl. A 4.0 injected would be a good swap, but depending on how much comes with it for 500.00 may be a long stretch to get it in for 1000.00. Can you get the complete motor, engine harness, power distribution center (pdc), and computer with it for 500.00? Biggest things that come to mind are the cps, you can sent your bellhousing to Novak and they can drill out the hole for it and make a mount for it for around 125.00 last I heard, then you have shipping both ways and will need a 4.0 flywheel for the cps to read, or you can spend about 300.00 at Hersco and get the front relocating kit for it, or if you fill lucky you can try to drill out the hole and make a mount yourself. I have heard it is not all that hard. Second thing is not as much but you need a speed sensor. 91 Wrangler is the only obd1 Jeep that had one (92 and later went to a electronic speedo) and you can get it from Autozone for around 75.00 but then you will need a adaptor for the CJ speedo cable housing to mount to it, or get one from Hersco for 122.00. CJ transmission the the 4.0 pilot bushing (Hersco) 114.00 so you are already at around 525.00+ and you haven't even turned a wrench yet. Search the net for 4.0 swaps, there is a ton if info out there. One in the CJ forum also http://www.jeepforum.com/forum/f8/of...thread-475002/
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post #3 of 7 Old 01-05-2012, 02:18 PM Thread Starter
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It's a complete parts jeep, so I'd have basically the whole engine, wiring harness, computer, the works.
If I cant drill it out, my uncle is a very capable machinist, it would be a cake walk for him If I cant.
You sound to have your bases covered, seems very doable on my budget, like you said, maybe a bit over but I'm not starving... yet haha, by the time the jeeps done maybe. I'm just starting research and so I figured this thread would be a good starting place.

If trans and T-case are good, would I have to worry about drilling out the hole for the cps, or could I just drop the whole drivetrain in? would you advise against that? would I run into any clearance or allignment issues with the new trans and tcase? I cant remember what they put in the YJ's, all I know is I've got the borg-warner t5 with a dana 300 behind it.
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post #4 of 7 Old 01-05-2012, 02:19 PM Thread Starter
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also, is it common for a lot of lifter clatter in the old 258?
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post #5 of 7 Old 01-05-2012, 11:59 PM
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A 95 4.0 would be the best choice if it was me. 91-95 are obd1 96 and up are obd2 and the earlier 4.0s found in the XJs with the renix injection, well I would not bother with one of them. Swapping the whole drive train wouldn't be a bad idea if it has a AX15 trans, but remember the Wrangler is a driverside drop transfercase, but you can get a clocking ring for around 100.00 and use your Dana 300 for the passenger side drop for a CJ, but if you use the trans and bellhousing you have the cps and would not require any thing special. Best thing for a 95 if it is a AX15 it would not be a internal slave/throwout assembly. Not sure about how common lifter clatter is. Mine is a 86 258 T5/300 Dana 44 rear, 3:31 gears and is pure stock with the exception of 30/950/15 BFGs but they are not all that big. It started the piston slap around 150,000 miles and now at 191,000 it is getting louder, but my valve train makes no noise, it uses no oil between oil changes, I am getting around 20 mpg, and just passed emissions with flying colors. If I didn't have a rebuilt 258 on the stand to swap in this spring I would do 4.0 swap in a heart beat. I have a Gm based throttle body injection system (junk yard) with timing control ready for it but I am thinking about the mpi off a XJ and swapping out the head for a 4.0 and going that way.
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post #6 of 7 Old 10-06-2013, 05:53 PM
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You can buy a harmonic balancer from hesco and attach the crank sensor on the front of the motor. The sensor is different but everything works the same except it reads from the balancer instead of the flywheel.
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post #7 of 7 Old 10-06-2013, 07:05 PM
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a 4.0 is fuel injection. add a weber carb to a 258 (4.2) and a fuel regulater and call it a day.

Rubicon Rich ,05 TJ Rubicon: PatriotJeepers.com
86 CJ7 258,T18,Scout Dana300,twin sticks,Dana44's,4W Disc, locked,35's,YORK OBA,Warn 8274,fullcage.
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