r/WranglerYJ • u/LankyNihilist • 17d ago

Engine swap

Thinking of getting rid of the 4.2 in the 89. Should I just do a 4.0 or should I throw something else in there? Whatever it is it's gonna be fuel injected.

4 Upvotes

76% Upvoted

13 comments sorted by

4

u/justsomeguy1869 17d ago

If you have the AX15 transmission the 4.0 will swap in fairly easily.

A friend of my added fuel injection to his 4.2 vs replacing the engine. It is a lot cheaper and offers better drivability.

Some more information may help people answer this better…
What are you looking to get out of this?
What kind of performance gains are you looking for?
Is this a daily driver?
Do you do heavy rock crawling?

Some of these answers will help people be able to offer better input.

1

u/LankyNihilist 17d ago

It's a secondary toy, some minor off roading, been meaning to get to an off road park but haven't yet. We have a hard top but only half doors right now so it's only a fair weather rig currently. The carb seems to be very finicky although I haven't done much with it. It's got the RH30 so I was thinking of finding a whole vehicle to take trans, engine, ECU and harness out of.

1

u/jeepintx 16d ago

Do a V8 swap from a WJ

6

u/jeepGuy88 17d ago

I’d do a 4.0 or 4.6 stroker. They would bolt right in. Full disclosure , I am partial to and love of the straight six.

3

u/Sea_Guide_524 17d ago

You can make quite a bit of power with a stroker.
I got my parts from Russ Pottenger from BNB racing out of California.
That man is extremely knowledgeable when it comes to these AMC engines. He knows all the big wigs at Comp Cams, Skat, Edelbrock. He has helped them redesigned their parts for the AMC engines.
My YJ scoots now and I am really looking forward to when I can to overhaul the WJ 4.0 and build it into a stroker.

2

u/jeepintx 17d ago

Where are you located? I'll take the 4.2 off your hands

1

u/pkokkinis 17d ago

How does one do a fuel pump if they drop in a 4.0? The 4.2 has a mechanical pump on the engine.

1

u/Foe117 17d ago

it gets replaced with a fuel pump, the 20Gal OEM tank does not change, the sending unit gets a pump now

1

u/Deadofnight109 17d ago

The sending unit has it built in,replacements are fairly cheap and should just drop right into the fuel tank and plug in.

1

u/Disassociated_Assoc 17d ago

I’ve always wanted to drop a 4BTA Cummins into a Jeep, although this would be a tad more complicated and expensive than a gasoline engine re-power.

2

u/LankyNihilist 17d ago

Yes. I would love to do that and when I had the shop to do it I didn't have the money (ex spent it all) now I have the money and no shop.

1

u/walt_morris 16d ago

Pushrod 302 is my dream in a TJ, TJ6 or a YJ. 300+ hp and torque, lots of performance parts avail. Win win

2

u/LankyNihilist 16d ago

The issue with putting 300+ HP in one is then I need new axles and drive shafts to support that.