• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Best Engine Swap?

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
do the 4.0 like me

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.
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.


In it to win it
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.
Last edited:
wow thats detailed

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.


Legacy Registered User
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
Last edited:


Perpetual Parts Collector
Lifetime Member
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

Legacy Registered User
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!


Legacy Registered User
amc 360 w tf999 auto

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.


Picture cravin' AK Postal nut
Staff member
SOA Member
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.
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. :(
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?


Perpetual Parts Collector
Lifetime Member
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.

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.