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Old 12-17-2013, 01:20 PM   #1
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87 Wrangler 4.2L engine replacement questions

I've just bought the jeep and it has a major engine knock to it. I bought it assuming that I'd have to replace the motor, my question is :

Should I just replace it with the same motor (but fully rebuilt)? Or should I take this opportunity to switch the motor. I've already got 33x12.5 toyo m/t that I'll immediatly be running on it and I plan on eventually going up to 35's or 37's. This truck will probably be 70 percent road driven and 30 percent crawling.

Any input on the engine swap would be appreciated.

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Old 12-17-2013, 01:26 PM   #2
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I put in a 4.0 the last time that the 4.2 died. In hindsight I kinda wish I put a v8 in it. That being said I'm happy with the 4.0 more then I was with the 4.2.

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Old 12-17-2013, 06:20 PM   #3
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I've got a good 4.2 in my garage if you are close to NW PA. If you are considering a swap to a different engine then you might as well look at a V8.
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Old 12-17-2013, 07:56 PM   #4
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I'm doing the 4.0 swap into my 88 YJ. There are A ton of threads on the pros and cons of doing a 4.0 vs a V8. I decided on the 4.0 mostly based on $$$ and convenience of not having to weld new motor mounts.

I'm slowing rebuilding the 4.0 now and I'll start a thread with pics this Spring when I do the conversion.

Have fun with your project. Hope to see some good posts about what direction you end up going.
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Old 12-17-2013, 09:25 PM   #5
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I'm considering a swap myself but don't know how far I want to go, I have a 4.0l that needs a rebuild that I'm considering stroking it out and putting it in or just rebuilding it. The 4.2l lacks balls even after I rebuilt it and bored it .030 over with all the performance mods I've done. Maybe I'm going to find a v8 myself, but I'm a broke ass college student right now with a part time job....
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Old 12-17-2013, 11:29 PM   #6
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Thanks alot for the input. I'm impatient as hell, thus the reason I'm really leaning towards a straight swap with the new 4.2 liter, but I've read a few things about installing the 4.0 head and injector setup on that.

Is it that simple to change the 4.2 into a fuel injected motor by changing heads and adding the rails / electronics that go along with injection?

I'd love to go the route of a V8 but I think I'll spend the majority of time in the jeep on the road (probably 70/30 road/offroad). I'm really going for just a toy that'll take me anywhere I want to go during hunting seasons.

As of now, I'm planning on dealing with the shortage of power (v6 vs. v8) through gearing and an ARB setup.

Do people still think I should get away from the 4.2?
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Old 12-18-2013, 12:37 AM   #7
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Quote:
Originally Posted by McKenzb View Post
Thanks alot for the input. I'm impatient as hell, thus the reason I'm really leaning towards a straight swap with the new 4.2 liter, but I've read a few things about installing the 4.0 head and injector setup on that.

Is it that simple to change the 4.2 into a fuel injected motor by changing heads and adding the rails / electronics that go along with injection?

I'd love to go the route of a V8 but I think I'll spend the majority of time in the jeep on the road (probably 70/30 road/offroad). I'm really going for just a toy that'll take me anywhere I want to go during hunting seasons.

As of now, I'm planning on dealing with the shortage of power (v6 vs. v8) through gearing and an ARB setup.

Do people still think I should get away from the 4.2?
The 4.2l is good for the low end torque, I decided to go with the 4.0l head swap to try that out myself. Might go fuel injected with all the mpi stuff from the engine I have, and keep the 4.2l.
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Old 12-18-2013, 05:24 AM   #8
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the 4.2 is a great motor when built right. it can easily put out over 200 hp with the correct parts, if you like to tinker/modify i'd run it, if you just want a dependable stock motor then the 4.0 is a good choice.
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Old 12-18-2013, 10:56 AM   #9
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Quote:
Originally Posted by roadyrob View Post
the 4.2 is a great motor when built right. it can easily put out over 200 hp with the correct parts, if you like to tinker/modify i'd run it, if you just want a dependable stock motor then the 4.0 is a good choice.
You fan get 200hp easily with just a camshaft intake manifold , carb and full exhaust. With those parts and a Flatlander stroker kit for the 4.2 you will be in the 300hp/350tq range.
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Old 12-18-2013, 12:38 PM   #10
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It's already got a weber Carb on it, that I've heard is a really quality aftermarket. I think I'm just gonna buy the re build kit for it and see if I won't have to change. I got to looking a little at the jeep last night and noticed hammer marks on the front of the block, and some major damage like some A-hole was trying to beat a crankshaft loose with a sledge. Now I'm really glad that motor's gonna get removed today.
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Old 12-18-2013, 02:00 PM   #11
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87 wrangler 4.2 engine replacement questions

Ive been there the first time I had it rebuilt the 4.2 but found that was not much of an improvement. Then got rid of all the emissions and used a 2100 motorcraft carb I had from a ford van that was better. The second time I found a 91 caprice w/5.0 and 700r. This time I rebuilt it and it has been a match made in heaven. Great power to weight ratio and a hell of a lot more fun to drive. I did have to change the output shaft from the trans to bolt up the tc. Otherwise used the same driveline on both ends. The biggest plus is if anything is needed for the motor or trans it's a chevy unlike anything related to MOPAR doesn't say bend over and grab your ankles when you get the price.

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