Engine Swap

[dasbrick]

What is needed for an engine swap from a 87 Renix 4.0 to a 95 HO 4.0? I understand the ECM in the engine bay, but what about the dash computer? Any sensors? Will the engine attachments match up? Will the output shaft line up to the input on the BA/10 transmission I got? Will the bell housing bolt up? I have never done an engine swap before, but I want to put some life into my MJ.

[freakjeep93]

the HO motor doesnt make a ton more power from what I'm told. i think youd be better off finding why the renix motor isnt making enough power

[dasbrick]

Well the more i am looking at it, I might stroke the 95 4.0

[jpnjim]

You can install an HO, and swap all the Renix sensors onto it (so you can keep your renix wiring & computer),

or you can install the HO + the wiring harness + computer.

 

I didn't do the complete (harness + ecu swap),

but I imagine that's mostly a plug & play + adapting some of the XJ wiring to work with the MJ (assuming you start with an XJ harness vs an MJ one).

 

 

 

I put an HO in, using the renix harness & sensors.

 

toughest part of that was adapting the renix TPS to the HO throttle body (not really that hard).

 

if you have an auto, you have to do it for the trans TPS too.

 

When using a Renix control system on an HO,

In addition to the sensors & TPS, you need to swap:

 

the flywheel (different cutout locations renix vs HO)

alternator (HO's alternator is regulated by the CPU)

Distributor (Tho I did not try the HO's to see if it would work)

 

figure out a way to adapt the Renix fuel lines to the HO's fuel rail (not too tough either)

 

 

You'll also need to get an HO throttle pedal assembly to work with the engine.

 

There's probably more stuff that I forgot, but search around here,

I thought there was a sticky here that covered this too. :hmm:

 

My '88 MJ build' link in sig has some of the details too.

[Pete M]

stroker + peugeot = boom

 

 

dollar for dollar, the best performance improvements are seen with regearing. :thumbsup: maybe add in some better injectors too.

[dasbrick]

If I stroked it, i'd track down an AX-15.

[Pete M]

and a new t-case to go with it.

 

Are you still rockin' the 3.07 gears?

[dasbrick]

you know it. i am thinking of going into the 4s.

[Pete M]

4.10s would certainly bring back the power. :D

[Incommando]

stroker + peugeot = boom

 

 

dollar for dollar, the best performance improvements are seen with regearing. :thumbsup: maybe add in some better injectors too.

 

 

I have been preaching that for years, but it is not as sexy to say " I regeared."

 

Here is something I posted just today on another forum:

 

I know that bragging rights are cool, but I question the need for any more horsepower in a KJ. All you will do it render the driveline more likely to break. Even for mall crawlers.

 

I had a 1981 CREW CAB Chevy C30 long bed pick-up with a 350/4v engine. That vehicle had 160 hp and 260 #'s of TQ. I towed a 7,000 car/trailer combo for ten's of thousands of miles, and the truck weighed almost 1,200 #'s more than the KJ, which has 210 hp and 230 #'s of TQ!!!!!!!!! Amazing that people can't get by with the KJ's power...

 

The one advantage the truck had was 4.56 rear gears. If you want more performance without destroying potential dependability and longevity, a gear swap is a much smarter, probably cheaper, and less impactful mod.

 

keep in mind that the KJ weighs about 1,000# more than an MJ.....

[dasbrick]

true but I'm getting a complete 4.0 HO engine to do this with for a trade of a camping stove.

[Pete M]

"just because it's a good deal, doesn't necessarily mean it's a good idea."

 

 

the problem with your truck now is gearing. dropping in a new engine won't change that. make sure gears are part of your plans. :thumbsup:

[dasbrick]

I plan to, just cuz of the cost, get this 4.0, stroke it, get an ax-15 and either regear the 30/44 combo I got, or drop a pair of 60s in it that a buddy has. I can't remember what the ratio was, but I think they are in the high 4.

[pilotblake]

You will have to excuse my lack of details, but I remember an extreme 4x4 show where the guy had a 4 banger toyota with steep gears and kept up with most of the bigger horsepower rigs. If you want a deep rumble and more horsepower drop in a V8, if you want the best bang for your buck as they say, regear. :yes:

[wyk]

You will have to excuse my lack of details, but I remember an extreme 4x4 show where the guy had a 4 banger toyota with steep gears and kept up with most of the bigger horsepower rigs. If you want a deep rumble and more horsepower drop in a V8, if you want the best bang for your buck as they say, regear. :yes:

 

 

Yep. If some of the folks that I have seen pay $300 for 'cold air intakes' put that money to gearing instead, they would have been a lot happier; especially the ones with big tires. If you do not need to speed on the HWY, put in the lowest gears your diffs can take. The only disadvantage I have seen with my 4:10's is the fact I have to putz around parking lots in second gear, or wind it out in first. I also went with a 3:73 locker in my 65 Mustang from a 3:08 and it was a HUGE difference. I then went from 3:27 or some such in my Hemi Dodge to 3:91's with an Eaton, and it was like adding 50 hp. That thing LAUNCHED. Gears, man.