Let’s Get Hypothetical!!!... CJ5 Engine Swaps

[neohic]

For reference, let’s consider a starting point of a ‘75 CJ5 with a current drivetrain of a 258/T14 with 4.27 Dana 30/44s and 33” tall tires. 

 

So... I’m not convinced that my 258 has lost that long term reliability that they’re known for. I was having some issues earlier this year with a clack and low oil pressure. This was “fixed” with rolling in a set of bearings. I’d call my oil pressure adequit but I catch myself watching the gauge more than I should. 

This gets me thinking about other options. Sure there’s the near bolt in option of a 4.0, but I’m stuck with zero overdrive transmission options. What about a shorter engine to compensate? Why not a 2.5/AX5 combo? I know... I know... its got to be some kind of sacrilege to replace a six cylinder with a four. But why? The early ‘90s Jeeps with the 2.5 made more horsepower than the 258s, but obviously less torque. The AX5 could prove to be difficult paring with a passenger side drop Dana 30... I guess a Dana 300 could be put behind it, but who does that? By moving the drivetrain forward I could still have a nice driver with adequate power and overdrive to make it a real road tripper. If you google “Project Ground Up” from Four Wheeler from a while back, they used a ‘98 2.5 XJ as a donor to power a ‘56 CJ5. They ended up stretching the wheelbase a little but I think starting with a long hood (‘72-‘75 for those not in the early/intermediate CJ realm) might have some benefit. 

Open floor here! I’m looking for some hypothetical “what if’s?” and “why not?” type of thoughts here.

[MeanLemons]

Staying with Jeep engines or are u open to any engines? 

 

Mercedes om617

1.9 TDI

 

with ax15/d300

or 

T-18 with d20 or d300.

 

some 4 cyl XJs had aw4 

 

maybe u could even find one of them and swap the drivetrain in. 

 

 

[Pete M]

I always wanted to build up a flattie with an obd2 2.5L   modern meets classic! 

[HOrnbrod]

Ford 289/302 Windsor V8. Adds a lot of scoot, and takes up little real estate, and can be adapted to 'bout any tranny config you decide on. 

[neohic]

19 minutes ago, MeanLemons said:

Staying with Jeep engines or are u open to any engines? 

 

 

I think so. Definitely need to stick with a manual trans as well. Simplicity is a plus too!

 

1 minute ago, HOrnbrod said:

Ford 289/302 Windsor V8. Adds a lot of scoot, and takes up little real estate, and can be adapted to 'bout any tranny config you decide on. 

 

Keep in mind that my little CJ has a 83.5” wheelbase. Even if it’ll fit, how much room does it leave for tube in a driveshaft?

[Minuit]

Didn't they put the AMC 304 in the CJ5 from the factory? I know I've seen a couple of 360s swapped in place of them. If I wanted to swap engines and keep it in the family, that's probably what I'd look at first. Dunno what kind of transmission options that would leave you with though. I have seen a CJ with a built 360 and 4 speed and it looked like an absolute blast. I think they sound amazing too.

 

With that being said, I think I'd almost rather have a 2.5 with an AX-5 than a 4.2 with the three speed T14 anyway.

[HOrnbrod]

First gen Broncos are close in length to your CJ Ben. As I recall, stock config was a  3-speed manual or auto. But the AX-15 can be easily adapted and is a popular swap for the early Broncos w. the 289/302. Dare to be different. For you it would be cake.   

[Pete M]

what about building a stroker 4.6?  it'd certainly look period correct and the rest of the drivetrain would remain untouched.  overdrive is overrated  

[500 MJ]

Yes the 304 was a factory offering in the CJ5. We had one, got me into the Jeep world and about killed me few times with that much power in the short wheelbase. 

[gogmorgo]

I bet you haven't thought about a certain provenance of very small, lightweight engines yet...

As a plus, it'll come with a CVT setup like a modern car, no clutch to worry about, even. Some of them even come with reverse!

 

I mean you did say hypothetical, right?

[shelbyluvv]

My 80 CJ5 had a 304, T176 and a 300 transfer. It was lifted 2" and I had plenty of drive shaft angle.

I think a 4.0, AX15 and 231 with a SYE would be a good fit.

[neohic]

13 hours ago, shelbyluvv said:

I think a 4.0, AX15 and 231 with a SYE would be a good fit.

 

Trying to think of options while retaining the passenger side drop front axle. Advance Adapters says an AX15 will never fit.  

[MeanLemons]

What about a Chevy 231? It’s a passenger drop. Unless the bolt pattern was entirely different?

[88whitemanche]

What about the 2.5L with an ax15/nv3550 combo? 

 

[shelbyluvv]

What about a Chevy 231? It’s a passenger drop. Unless the bolt pattern was entirely different?

Or a 241? They are both passenger drop?

[neohic]

10 hours ago, shelbyluvv said:

22 hours ago, MeanLemons said:

What about a Chevy 231? It’s a passenger drop. Unless the bolt pattern was entirely different?

Or a 241? They are both passenger drop?

 

The Chevy 231 is a driver side drop yet. 241s are passenger drop, but they also hang down pretty far, and they’re also getting harder to find because that’s what everyone likes to use for LS swaps on the cheap. Pretty sure a 241 would physically bolt up, but the spline count would be different. 

 

10 hours ago, 88whitemanche said:

What about the 2.5L with an ax15/nv3550 combo? 

 

 

Only reason I suggested the 2.5/AX5 combo was because I have that setup somewhat available. 

 

Not to have everyone feel like I’m just knocking down their suggestions, but I really am enjoying this! Everyone’s suggestions have gotten me thinking but I keep circling back to three options:

 

1. Replace the 258 with a 258 when the time comes. Live with the higher RPMs at cruising speed. Enjoy the simplicity. 

 

2. Replace the 258 with a 4.0 when the time comes. Keep the T14. Keep the throttle body injection because it’s still practically brand new. Enjoy the simplicity but always know that I left a ton of potential on the table by not swapping in the multi port injection. Live with higher RPMs at cruising speed. Enjoy the simplicity. 

 

3. Replace the 258 with a 4.0 when the time comes. Keep the T14. Add 300% more wiring to the Jeep than it already has and keep whatever fuel delivery the 4.0 donor has. Live with higher RPMs at cruising speed. Loose the simplicity. 

 

4. Replace the 258 with a 2.5 when the time comes. Swap in a AX5... or 15. Figure out a transfer case. Add 300% more wiring to the Jeep than it already has and keep the multi port injection from the donor. Enjoy lower RPMs and keep up with tragic. Loose the simplicity. 

 

So, again... thoughts?

[Pete M]

the simplicity is one of my favorite parts of old iron    

 

how high are these rpms getting and how often are you going that fast?  I mean, my dakota has 3.92s with 27" tires.  2.5/auto came with 4.56 pushing ~28s.  or is it more the noise of the engine at those speeds?

[HOrnbrod]

29 minutes ago, neohic said:

The Chevy 231 is a driver side drop yet. 241s are passenger drop, but they also hang down pretty far, and they’re also getting harder to find because that’s what everyone likes to use for LS swaps on the cheap. Pretty sure a 241 would physically bolt up, but the spline count would be different. 

 

Only reason I suggested the 2.5/AX5 combo was because I have that setup somewhat available. 

 

Not to have everyone feel like I’m just knocking down their suggestions, but I really am enjoying this! Everyone’s suggestions have gotten me thinking but I keep circling back to three options:

 

1. Replace the 258 with a 258 when the time comes. Live with the higher RPMs at cruising speed. Enjoy the simplicity. 

 

2. Replace the 258 with a 4.0 when the time comes. Keep the T14. Keep the throttle body injection because it’s still practically brand new. Enjoy the simplicity but always know that I left a ton of potential on the table by not swapping in the multi port injection. Live with higher RPMs at cruising speed. Enjoy the simplicity. 

 

3. Replace the 258 with a 4.0 when the time comes. Keep the T14. Add 300% more wiring to the Jeep than it already has and keep whatever fuel delivery the 4.0 donor has. Live with higher RPMs at cruising speed. Loose the simplicity. 

 

4. Replace the 258 with a 2.5 when the time comes. Swap in a AX5... or 15. Figure out a transfer case. Add 300% more wiring to the Jeep than it already has and keep the multi port injection from the donor. Enjoy lower RPMs and keep up with tragic. Loose the simplicity.

 

 

^^  These options are not hypothetical - they're boring.    But #2 is probably the one that's easiest and the least boring and the most bang for the $$.  Then later on MPI if and when you're bored again...

[MeanLemons]

You sure bout that? I have seen passenger side drop 231’s.... 

[FrankTheDog]

Look up five for fire for using a stock 4.0 HO injection setup. There isn’t that many wires to a 4.0 HO.

 

Or, you could put a Clifford 6=8 2 or 4 barrel manifold on it and run a ford 2100 or 4100 carb and put an hei distributor in it and have even less wires. Use a GM one wire alternator too.

[neohic]

On 10/18/2018 at 8:17 PM, MeanLemons said:

You sure bout that? I have seen passenger side drop 231’s.... 

 

Do you recall what model it was under? I thought the 231s only made it into the S-10s and Blazers with IFS. We did a 5.3 swap in a YJ a while back and we used bits from a 231c and the stock 231j to make it all work. Both were driver side. 

[DirtyComanche]

20 hours ago, MeanLemons said:

You sure bout that? I have seen passenger side drop 231’s.... 

 

I agree.  I don't know what the application was, but I remember always running into them in the PnP.  Chevy or Dodge something, would have had to be in the transition years in the late 80s/early 90s, I think.  But I honestly don't know, that was a long time ago.

 

I'm trying to get a passenger drop 241 for a contingency option on one of my current projects.  They are rare now.  I don't know why guys are using them for LS swaps, there's better options.

[Money_Pits]

I think the isuzu mua5 tranny (from behind a 2.8l) will bolt to the 2.5l and is a passenger side drop? maybe the aisin ar5 from a late model trooper also? I'm not sure if it is passenger side drop, but it is technically an ax-5 (edited: it appears to fall between an ax-5/ax-15) and has the right bolt pattern for the 2.5l. Starter location may be an issue.

[neohic]

On 10/18/2018 at 7:26 PM, neohic said:

2. Replace the 258 with a 4.0 when the time comes. Keep the T14. Keep the throttle body injection because it’s still practically brand new. Enjoy the simplicity but always know that I left a ton of potential on the table by not swapping in the multi port injection. Live with higher RPMs at cruising speed. Enjoy the simplicity. 

 

On 10/18/2018 at 8:04 PM, HOrnbrod said:

 

^^  These options are not hypothetical - they're boring.    But #2 is probably the one that's easiest and the least boring and the most bang for the $$.  Then later on MPI if and when you're bored again...

 

I'm leaning towards this boring non-hypothetical solution as well. With keeping the T14 three speed, my main gripe is the huge gap between gears and the lack of an overdrive. Granted, 3rd gear is a 1/1 ratio and with the 4.27 gears and 33" tire (measuring to 32") puts me just shy of 2700 RPMs at 60 MPH... which isn't terrible. Sometimes just driving around town feels like it just doesn't have the right gearing though. At 30 MPH, 3rd gear feels too low while 2nd feels too high. Around town driving sure felt better with the old 32" tires (measuring just over 30") but it always sounded like the engine was ready to set up an impromptu yard sale of ejected parts. Perhaps without completely hitting the reset button that hard and leaving the majority of the hard parts as and where they are might be well enough.

 

Let's swing the conversation over to a non conventional 4.0 swap. Having a quick look around in the internet land, there are a ton of forums that start with the guy saying "my fuel injection isn't working right, can I put a carb on my 4.0?" that is quickly followed up with a pile of ridicule. I know a 4.0 will run on a carburetor and therefore will run off of my current Howell based throttle body fuel injection/DUI ignition. I also understand that the 4.0s rely on spark control and knock sensors (Renix, anyhow) to make the best of the higher compression than the 4.2s. The 4.0s are a higher reving engine than the 4.2s making me want to believe that it would live a happier life in front of a three speed transmission... but is probably a moot point.

 

Say I do a 4.0 swap and run it off of the throttle body injection. Would it matter is I were to use a Renix or HO as a base? What about ruling out a 4.0 from a WJ?... I know... I know... the motor mounts are different. Pretty sure the '81+ carb intake manifold I have will work on either head with a little port matching and with the correct bridging washer will work with either of the exhaust manifolds. What about alternators/accessories? Would it make sense to just leave my V belts being everything works as it should?... they should directly bolt on depending on the intake manifold I'd use?... right?

 

Or am I just over thinking everything? 

[HOrnbrod]

Now THIS wouldn't be boring.