View Full Version : Best Engine Swap?

06-21-2007, 10:53 AM
Toying with the idea of keeping the Scrambler (wife has already agreed) but this will definitely require performing an engine swap to make it long distance at 65 mph and partly to satisfy my need to tinker. :D

Was considering dropping in a 4.0 fuel injection engine with an automatic w/overdrive from either a Grand Cherokee or TJ. But want opinions, keeping in mind:

1. Willing to give up hot rod power for fuel economy but not to the point of driving an anchor. Also realize less power doesn't really mean more mpg.

2. Needs to be fairly straight forward. Don't mind a few custom mounts or a little bit of rewiring, but I don't want a two month project.

3. Adapter to the Dana 300 must be available.

4. Exhaust sound must be kept quiet (I like to hear myself think and have never been fond of exhaust noise).

5. Getting A/C is a must of the engine swap since if I do the swap, running a hard top will be in the future.

6. Engine must be readily avaible from mid 80s to late 90s as these are what I can get at the discount u-pull yard.

Don't worry about mentioning the 4BT as I'm already looking into that one. Just concerned with the noise from the diesel.

So convince me. Oh, I also love links since I really like to over research my choices. :D

06-21-2007, 10:35 PM
its a matter of gas verses power than the 4.0 wins in my opinion. besides i am having difficulty understanding the wiring aspect of the job and could use some advise as well. i am doing the 4.0 at some point. i already have the donor.

06-22-2007, 07:29 AM
5.0, Good economy on the road, power to weight ratio is way better than with an I6, Parts readily available, quiet with the right exhaust setup.

06-22-2007, 12:53 PM
4.0 head and efi conversion if the lower end of your 258 is solid, that way you can help me with mine...

06-22-2007, 02:47 PM
5.0 = 304 V8 Would be my choice. See Above.


06-22-2007, 04:12 PM
The 4.0 Swap into a CJ is 4 wires to get it running.

I have a 4.0/AW4 combo out of an XJ in mine. Easy swap, and Novak sells an adapter to easily mount the D300 to the AW4, clocking it almost flat in the process.

The XJ had AC, so if you really want it, it would only be a matter of plumbing it in. I'm turning mine into OBA.

Motor mounts are a slam dunk

You can use your stock radiator

Routing the 4.0 harness and computer is a bit of a chore, but nothing too difficult as long as you're patient.

06-23-2007, 09:34 AM
I am planning a 4.0 swap myself and would like to document the whole process to help others (like stu). Anyway here is a pretty descent link I came across makes for some good info/planning http://www.4x4wire.com/jeep/tech/engine/fi40swap01/

06-25-2007, 11:29 AM
thanks for your explanations. i am in the middle of doing the same swap and now all the info is on one page. this is a big help thank you very much.

06-25-2007, 08:40 PM
ramjet 502:evil: but out of all seriousness i would think about doing a ramjet 350 with turbo 400 to an atlas but that isn't cheap. A 4.0 is achievable in a weekend and is slightly better than a 258.Golens makes a stroker motor for a pretty reasonable price for a good amount of horsepower. For simplicity and power i would go the golens stroker with howell fuel injection

06-25-2007, 08:48 PM
Cummins 3.3 bt.

This is a different animal, but has a great milage factory.

It is a little 2 cyl based on the 6bt and 4bt. But a little shorter and less weight.

There is a little info out there. A guy on the Deisl forums has done a conversion in a YJ so it can be done.

Google "Cummins 3.3 jeep"

Or just go simple and find a early Throttle bodied chevy 350 in something like a K2550 and swap in V-8 with a 700R4 or a 4l60e for OD fuel stretching.


Super 8
06-25-2007, 11:07 PM
I have a CJ with a TBI 350, CJ8 with 5.3L Vortec/4L60E, and a CJ8 with a Cummins 3.9 4BTA/ NV4500. Of all of them, I like the diesel best!

06-26-2007, 01:07 PM
i went with amc360 out of a full size jeep. had a tf999 auto trans rebuilt. upgrade ign system.regeared the axles with 3.73s it gets better fuel milage the my yj with its 4 banger. and even the 98 tj with 6 cly. just have to keep my foot out of it.

06-27-2007, 01:21 PM
IIRC Scott Anderson was claiming some very impressive mileage numbers with his LT1. Really changed the way I think of that swap...

Ask him about it.

06-28-2007, 12:13 AM
i get 15 consistantly out of a amc 360 2bbl carb backed by a t18 and 4.10 gears on 33's

06-29-2007, 07:41 AM
I've got a TBI 305 with the stock T176 and D300, and Novak Adapter pieces to make it work. I took it out of a totaled Caprice, so the harness and everything else came with it. It's run beautifully, the install is clean and simple, and I've been getting about 16 mpg. My exhaust has a little rumble to it, but that's just a matter of what you want under there.

Unfortunately, I filled the gas tank with muddy water during our most recent trail ride, and I know some nasty got in the intake. After it goes back together this weekend, we'll see if it still has that pleasant rumble. :(

01-09-2008, 09:28 AM
Been looking at this again and doing a lot of reading on CJoffroad.

Have decided that if I do a swap it will be an engine/transmission swap to be mated to my Dana 300.

Stephanie wants to keep it Jeepish so that means a 4.0 w/TF904 from a YJ or a 4.0 w/AW4 from a Cherokee. Concern with the AW4 is reading on Novak page how the AW4 is a little inefficient and doesn't have stellar reviews. Best part of these two options is I can get the engine/transmission/wiring/ecm from the local u-pull yard for under $500 complete with all the accessories. And since I arleady have a clocking ring, no other adapters are needed. Also, since I have 4.10 gears and 35s, the O/D of the AW4 will be useless (unless I drop back down to 2.5" lift and 33s which I have been considering though unlikely)

I on the other hand have been considering the Chevy 4.3 w/TH350C since I think think the 4.3 has a little more power, more fuel efficient, and the TH350C is a stronger transmision. While I can get all of this from the same u-pull for the same price, it seems more work since I have to change out the TC input shaft which is an additional $500.

Both options will require a new rear driveshaft but I have a coupon that will cover that. Front driveshaft isn't an issue since I'm still running the PTO shaft which has 20+ inches of travel.

Of these two options, which would be the better choice?

And, figuring that I can grab just about any common engine from early 80 to 97 for the same cost, have I missed a good option?

01-09-2008, 10:16 AM
The 4.0l and 999 from a YJ if you can find it would be the quickest, as there is not that much to figure out. Also pretty strong and simple. Will look almost factory too.

Now the chevy will offer a lot more options as far as aftermarket support, and the th350 is pretty easy to do. The TBI injection is a nice and easy swap. Vortec is a bit more work.

Either way I would look to stay 95' or older so that you stay with an OBDI computer system. Just easier to figure out and trouble shoot.

BTW, a S-10 is a good donor for the chevy V-6.


Ted Wendel
01-09-2008, 02:51 PM
You can't go wrong with a 4.3 either,a 700R4 would be good also,but you would have to regear.

01-09-2008, 06:57 PM
Keep it Jeep. :D

01-10-2008, 12:56 PM
Went to the junkyard browsing today and decided that for the engine swap, I'll be keeping it jeep and going with a fuel injected 4.0. The junkyard didn't have any YJs but between looking at XJs and Chevys, the 4.0 meets the simplicity requirement so much better. Now to just figure out which years are good candidates (?? - 95) and start looking for a donor.

In the meantime, I'm also going to be doing research on just swapping my existing motor to FI since the bottom end is fairly strong. While the stroker is interesting idea, just more complicated than I want to get. The transmission can be taken care of by tearing it down for an over haull which should be a simple weekend chore.

01-10-2008, 07:51 PM
91-95 is OBD1. I did my swap with a 96 XJ; OBD2 can be done. With the help of the 4.0l swap forum, on cjoffroad.com, the fuel system was harder than the wiring.

01-10-2008, 09:47 PM
I'm facing the same quandry myself, low miles, tight 258 but it wants efi and I am doing the same if then analysis you are. I'm thinking right now of a 4.0 head and factory efi but haven't found the stuff yet. But, I've been told its easier to just do a complete motor. Mine indecision is exacerbated by the fact that I JUST finished installing a new 999tf. I should have ( I think) gone 4.0/AW4 but the cost and rebuild cost was to high plus my 258 only has 80k on it

So, I'm VERY interested in what you decide and how you choose the direction you ultimately take

01-11-2008, 12:06 AM
I do believe there is a little to much Stephenie in this project. Who wears the pants.....

Got to go, for got to take the trash out and the wife is ticked.

01-11-2008, 04:29 AM
91-95 is OBD1. I did my swap with a 96 XJ; OBD2 can be done. With the help of the 4.0l swap forum, on cjoffroad.com, the fuel system was harder than the wiring.

I agree, OBD1 is the way to go, at least for my ability and technology at hand. I spent weeks splicing a 94 OEM Wrangler Harness into my CJ bulkhead. Grant it looks factory, but should I do it again, I will save for buying a custom built harness from Hesco. The input and threads from cjoffroad where important reference.

01-11-2008, 10:48 AM
...but should I do it again, I will save for buying a custom built harness from Hesco. The input and threads from cjoffroad where important reference.

I have been watching this posting and based on my experience, a lot of good information has been posted. I did the 4.0 HO/AW4 swap eight years ago before the cjoffroad.com site existed. There was plentiful information on the web then about the 4.0 swap but none on the AW4 side of things. I was lucky to find a 92 XJ with 62k miles that was totaled, which I salvaged out. I did not even know about OBDI versus OBDII issues until reading cjoffroad.com.

I agree about the Hesco wiring advice but the last I knew, it did not accommodate the AW4. You might want to check that out. Other things you need to be aware of are that the AW4 is about 5” longer than the T4/5 and the 999. (I can not find what your current tranny is.) This means accommodating in some way that the stock t/c linkage will be 5” back. I ended up modifying a Currie twin stick. While you can use the stock skid plate modified, you will not realize the clearance gains until you have a custom skid plate.

You will have to fabricate transmission cooler lines and have a transmission cooler. I placed a cooler in front of the radiator and then eventually put in a three-row radiator with transmission line connectors and now use both. If I had it to do over again, I would buy a cooler with fan motor and place in the area under the battery tray and eliminate the long lines, etc.

Another item that took a lot of time was the transmission shifter. Nobody that made custom automatic shifters at that time, such as Lockar, could tell me if it would work on an AW4. They would just say buy it and try it. I do not know if this has changed or not. I ended up building a custom console that accommodated the XJ shifter and linkage. This took about three versions over a couple of years to get one that looked appropriate.

I have been very happy with this swap/conversion once I got all the issues fixed. I took me about a year to get it working the way I wanted but answers to most of my issues are now on cjoffroad.com. I am curious to know why Novak was critical and I will check out their web site.

On the 4.0 part of the swap from an XJ, there are a few other issues, which are well covered at cjoffroad.com.

Later, Ken

01-12-2008, 01:15 PM
...I am curious to know why Novak was critical and I will check out their web site...

As a follow up, the following is what is found on the Novak website:

“The AW4 is a light to medium-duty transmission. Ours, our callers' and customers' experiences with the AW4 are less than stellar. They have a tendency to generate excessive amounts of heat, and are known for unnecessarily consuming more engine power than some other automatics. The shift points in the AW4 feel odd, and the spotty engagement of the lockup torque converter is idiosyncratic.”

I can not disagree with any of this but this is what I was referring to in my 01/11/08 post, “It took me about a year to get it working the way I wanted…”

The excessive amount of heat and the power loss comes when the torque converter is unlocked. During that post swap year, I was fortunate to find a link on the NAXJA forum to a website that detailed how to wire the shift solenoids and torque converter so that the driver could control the shift points and the locking/unlocking of the torque converter. It only included first and second gear, I use the AW4 shifter for third and fourth. This web article is no longer available but there is now a product that can be purchased to accomplish the same: http://www.awshifting.com/ and here is an article on it’s use: http://www.stu-offroad.com/engine/awshift/awshift-4.htm

Later, Ken

01-13-2008, 08:55 PM
This web article is no longer available but there is now a product that can be purchased to accomplish the same: http://www.awshifting.com/ and here is an article on it’s use: http://www.stu-offroad.com/engine/awshift/awshift-4.htm

There's an article on buying high mileage Jeeps in JP this month where they state that the AW4 is a solid tranny that they liked.

I still think that it's the ideal DD/weekend warrior setup with the 4.0 and the awshifting unit that does the auto/manual operation... I'm planning on doing that in the future DD Scrambler build I'll get to one day ;)

There's a very cool crawl box you can build out of a 231 that will then bolt to a D300 and serve as the adaptor, it's on Pirate somewhere... I thought that would be great with the wheelbase in the Scrambler.