New engine

[Dmac2590]

my yj needs a new engine it has a 2.5 with 197k and i dont know if i wanna put a 4.0 in or just rebuild my 2.5 if i do a swap what all will i have replace to complete the sway i know i have to replace the motor tranny motor mounts and the wiring harness is there anything else that needs done?

[jlovbasz3]

I believe you got to swap the t-case. I've heard many people say the 4.0 is a great engine but not worth swapping into anything? Maybe a V8??

[Dmac2590]

i would love to find a nice 350 but the kit is a lot of money

[Mykal]

This will tell you everything you need to know.

[village_idiot]

5.2 swap!

[DixieJeeper]

its actually easier to swap a SBC 305/350 into versus a 4.0. You can cut the 2.5L mounts out and bolt in SBC plus all the other necessary nonsense. Whereas for a 4.0 you need to cut the mount perches off the frame then weld in donor mounts farther forward.

It is often said the 4.0 is a great jeep engine but not great enough to swap into anything.

If you are hellbent to do the swap:

best thing is to get a donor complete running rig of same model/near year and make it happen- its alot of work and alot of headaches. Pick up last months JP or 4Wheel and Offroad. DId a whole article on engine swaps.

4.0 if you do a top of the head list:

known good 4.0L complete intake to exhaust
4.0L engine harness, injectors, and PCM
Frame horn mount brackets and new mounts
If you have a AX5 (manual 4 cylinder) you will need to swap in a AX15 manual for 6 cylinder
Swap the input gear for the NP231 transfercase there is a splinecount difference ax5 vs ax15
Clutch disc and pressure plate

If you have an auto you will need the donor felxplate and the donor starter

Thats just the top of the my head and assuming you get a identical model and year jeep to swap everything out of.


I would recommend repairing your jeep with what you have. The 2.5L isn't a bad motor. Its just as strong as the 4.0 in realiabilty, you need to gear the rig correctly to keep your power on the street and some improvement on the trail. 31-33s 4.10s are nice, 33s up I go more agressive the near "5" range or deeper.

What I found with my 2.5 even before the turbo was a 4:1 transfer case really woke it up offroad and at that time I was running 3.73's now with 4.10's its terrific. I also find my 2.5L is the most balenced off road as far as weight too.

Having had a jeep with a SBC conversion I found it heavy on the front end and had a propecentity to "hump" the rocks before it crawled over them.

In the end if you are totally convience you want to do a swap... save up the cash.. get a low mile SBC from the wrecking yard.. for about 900 complete with an uncut harness. If your luckily you'll score once with TBI or TPI injection and just need about 300 worth of engine cradle and mounts, plus whatever you do for trans adaptation.

I would shy away from ANY OTHER swap aside from SBC... it is the most common, the most supported, the most documented. I like to think anything that is rare and exotic in the swap land are harder and longer and in the end more frustrating. Even Ford SB swaps are uncommon, HEMI is a newer swap (if we are speaking of late models) and really is a big pain the ass if you ask my opnion and the SBC is far cheaper.

[gonecheenin]

I did the 4.0 swap to replace my carb'd 4.2 in my '89 YJ - it wasn't hard since I bought everything I needed out of a wrecked '95 (also didn't have to move mounts on mine), I'm very happy with it, and would be for the future if it was a daily driver.

That said - it's just a weekend toy & I wish I'd done the V-8 for the fun factor.

[village_idiot]

Got the wiring done for you.
http://cgi.ebay.com/ebaymotors/Jeep-...item5ae29594fc

[scramblur]

Find a tbi 350 no kit needed. Get the harness and trans with it and it is very simple to get rid of the wires that are not needed. A set of universal motor mounts from summit or JC Whitney and a t case adapter(biggest expense).

[DixieJeeper]

If you really feel the need there are a nuber of companies now that make plug and play wiring for common engine swaps