which engine size is best in a Jeep CJ7 - JeepForum.com
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post #1 of 21 Old 01-30-2007, 10:00 PM Thread Starter
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which engine size is best in a Jeep CJ7

I'm looking to buy a Jeep CJ7, which is the best all around engine to go with, a V8, 6, or 4 cyl.? Does the 4 cyl. have enought power. How about torque, are they close or is the V8 way ahead of the 4 cyl. New to Jeeps, figured I'd ask the experts. Thanks for your help.

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post #2 of 21 Old 01-31-2007, 12:20 AM
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IMO, when looking for a CJ to buy, Id would focus on certain year ranges rather than engines. For example, there are many differences between a 76 CJ-7 with a 6 cyl and a 86 CJ-7 with a 6 cyl. While both have a 258, there are different transmissions, t cases, axle widths, frame differences, interior and option differences, etc. But MAINLY look for a rust / dent free frame and body. An engine is just a component and can be swapped out for another one in an afternoon.....but if the body and frame are rusted and falling apart, you'll battle that for years and may not win (without going broke anyway).
To answer your question, the 6 is the most common and the most liked due to the touqe at low RPMs. There are two 4 cyl engines, a GM and an AMC. Both seem under powerd, but at least the axles are geared 4.10s. The only CJ V8 is a 304 and most will tell you if you'r going with a V8, go 360 or 401. I have both the 285 (6) and the 304 and like the 6 better for overall use. ...but my 304 is 31 years old, worn out and loud.....so I'm not speaking fairly.

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post #3 of 21 Old 01-31-2007, 02:01 AM
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Also consider what you're going to use it for, I only use mine at weekends as I have a company car as a daily driver, which is why I've just swapped from a 20mpg 6cyl to a 360 V8 which I haven't worked out yet but I'm guessing does less.

As 'only in a jeep cj' said I was more interested in the body / frame condition than the engine but in an '86 over here they only come with a 6cyl anyway.

Good luck

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post #4 of 21 Old 01-31-2007, 05:27 AM
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Originally Posted by only in a jeep cj
To answer your question, the 6 is the most common and the most liked due to the touqe at low RPMs.
I have both the 258 (6) and the 304 and I like the 6 better for overall use.
The best engine really depends on what you are gonna use it for.
My CJ 7 has the 258cc 6 cylinder engine and a five speed tranny. I can get my 31.5 X 10s to spin on dry pavement. Not like I would be able to do in a V8, no doubt. Of course, either will easily spin tires in dirt, rock, sand, etc. The thing about 4WD is having traction. Sometimes, more power is not better. Most trail driving is at low speed and the low RPM torque of the six shines.
The wheelbase on CJs are not the greatest for high speed driving considering many have quirky steering. My 6 will comfortably do highway speeds but I do wish sometimes that it had more subtle power such as passing abilities at highway speeds or climbing some of the tall long hills (highway travel). Of course I can drop it down to fourth gear but I still sometimes think V8.
On the other hand, performance gains can be made on the 258 6cyl.
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post #5 of 21 Old 01-31-2007, 05:43 AM
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20mpg with the 258 I6? I don't know if something's wrong with mine, but I ususally do about 10-13mpg.

Anyways, when I was looking I wanted a CJ7 with the 4.2L 258 I6. IMO, it's easiest to find aftermarket for this motor because it was the most popular. Not to mention, it's a great motor and seems to last forever. I had the 258 I6 in my 87 YJ and sold that with over 220k miles and she was still running strong. It had never been rebuilt or anything, and didn't leak or burn a drop of oil. My CJ7's 258 I6 is at 134k miles and still runs great although that wonderful plastic valve cover AMC used is leaking oil down onto the exhaust manifold. It's one thing after another on these things...

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post #6 of 21 Old 01-31-2007, 06:23 AM
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I get 20 with my 151. AS for jeep stuff, marmaduke and only in a jeep are dead on! foundation, foundation, foundation. I only have the 4cyl in mine and this being my first jeep it probaly saved me on more then one occasion learning the little nuiances on how to drive a jeep safely. Granted it dosent pull up a hill very well but the lack of horsepower also gives you a few extra seconds during the "oh shoot" moments. the 4 has great torque in 1st and 2nd for traill riding and 3rd is good for getting up 40 ish MPH but after that in 4th you better be on flat land or going downhill with the wind if you want 60.

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post #7 of 21 Old 01-31-2007, 07:06 AM
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I had the 258 for years ad I agree it is a great motor. But when I put the 33's on it Then I realized I want and need more Power so now I am putting in a 401. So it will come down to what you want as far as power
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post #8 of 21 Old 01-31-2007, 07:29 AM Thread Starter
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First. Thanks for all the replies, a lot of good info to think about.

The main way I would use the jeep is to go back and forth while hunting and fishing. Using it on dirt roads, having to go through mud at times. Something to get me there and back. Thats why I wasn't sure if the I4 would be strong enough for that, or do I need to go with at least the I6 or V8. Since I'm not driving it a lot on the highway, the four may be okay. Just want someone's opinion has or had one. Again Thanks

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post #9 of 21 Old 01-31-2007, 02:50 PM
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I've got two CJ7's at this time. One with the 258, (I-6) and one with a 151
(4 popper). Both have been used from daily rides to now weekend and snow plow work. I find that both could do the task that you want a jeep for. The only draw back I found for the 151 was lack of power for climbing hills. It's running 31x10.5x15's. When loaded with camping/hunting gear, it's a dog on hills. However, I use this jeep for snow plowing and it does a hell of a job. It also gets better gas mileage then the 258 with a quadra-trac xcase (full time 4wheel drive). If was getting a jeep be it a CJ YJ or TJ I would go with the bigger engine. You can't beat power. Just my 2 cents. Goodluck.
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post #10 of 21 Old 01-31-2007, 03:45 PM
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454 FI , it fits, but has plenty of torque.

I would stick with a 6 cyl and have it geared for your set up tires, lift, etc.

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post #11 of 21 Old 01-31-2007, 03:56 PM
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I would look for one with the Inline 6 and proper gearing for the tires..Thats key...I have the 6 pack in my 7 and dread the 3.54's with 31's..Going to eventualy swap them out to 4.56's...and bigger meats.

**********edit*******I should have read the last post...

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post #12 of 21 Old 01-31-2007, 04:17 PM
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I dig my 304.... that is, I think if it werent so beat to hell and tired.. it'd be perfect. I'm upgrading to a rebuilt 360 in about 6 months. I was going to rebuild the 304 but the guys on here talked me into the 360. Go figure.
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post #13 of 21 Old 02-02-2007, 06:51 AM Thread Starter
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any more! thanks for all the replys so far.
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post #14 of 21 Old 02-02-2007, 08:15 AM
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It wasn't the engine I was concerned about but the rest of the cj. When checking it out I noticed the front rotors had grooves and was able get a reduced price. It turned out I had to dump $400 to replace rotors, bearings, hubs, spindles. Just make sure you check the entire rig out. It has the 6 and I love it. 99% of the time it is off road. Might go with a v8 later. Good luck
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post #15 of 21 Old 02-02-2007, 09:16 AM
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Ramjet 350, they look perfect under the hood and probably perform well to. Sure wish my pockets were deep enough to afford one.
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