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Old 05-20-2012, 12:34 AM
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Lightbulb 4.0 i6 .v.s. 4.7 v8

What have you seen as Pros and Cons????



I own a 4.7V8 and a 4.7V8 H.O and i love those engines,But my Girlfriend has 4.0 and its fun to drive also.Jeep Has Strong Engines In the WJ's all together i think!!!!
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Old 05-20-2012, 06:25 AM
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Re: 4.0 i6 .v.s. 4.7 v8

It's kinda a no brainer for me. The 4.7's will out gas mileage the 4.0 every time. Why drive a six when a v8 gets better gas mileage? Don't get me wrong the 4.0 is about as bulletproof as you can get,just not very efficient.
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Old 05-20-2012, 10:56 AM
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The 4.0 is a solid engine, and has plenty of power for the jeep but not as good for towing. The 4.7 gets as good or better mileage and has plenty of power to move the truck and a load. Might not be as solid but that still remains to be seen as they continue to age.


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Old 05-20-2012, 11:19 AM
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Re: 4.0 i6 .v.s. 4.7 v8

4.0 is stronger and lasts longer but 4.7 is a lot better for towing and gets better gas mileage.
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Old 05-20-2012, 11:49 AM
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Re: 4.0 i6 .v.s. 4.7 v8

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Originally Posted by cheapjeep View Post
why drive a six when a v8 gets better gas mileage?
Because life isn't about skimping and gas mileage. If it was all about gas mileage, I would drive my Mustang (that gets better mileage than either engine option, 25mpg). If gas mileage is that big of a deal, why choose a Jeep?

I chose the I6 because it's pretty damn bulletproof and I drive 70 miles every day to work and back. Plus the maintenance cost of the I6 is less than the V8. I can throw cheap antifreeze and oils in my Jeep. With the different metals of the V8 block and head, you'll spend more more money on the Mopar special fluids and oils.

But at the same time, the I6 is underpowered for the 4,000 lb WJ. It seems to work good in the XJ's that are lighter, but it lacks in the heavy WJ. If you have any need to have power or need to tow anything more than a mower, you should get the V8.

You won't go wrong with either, it all depends on what are your needs.
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Old 05-20-2012, 10:35 PM
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Re: 4.0 i6 .v.s. 4.7 v8

Purely looking at the motor, the i6s will outlast the V8s. Maybe I was just unlucky but I think the 42re transmission that comes with the I6 is kind of a weak link where as the 45rfe on the V8 seems plenty strong, it even gets put behind the bigger hemi engines. You have to look at the whole vehicle sometimes, an engine doesnt do much good without the rest of the drivetrain.
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Old 05-21-2012, 01:44 PM
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Re: 4.0 i6 .v.s. 4.7 v8

good luck getting 230xxx plus miles out of a 4.7

every 4.0 ive owned has gotten atleast that mileage
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Old 05-21-2012, 07:28 PM
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There are 4.7's out there with that many miles believe me. Just like there are some with less. Not every 4L made it to high mileage either.

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Old 05-21-2012, 08:31 PM
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Re: 4.0 i6 .v.s. 4.7 v8

A lot has to do with maintainance and abuse. I bought my jeep with 111,900 miles and the 4.0 I6 was blown, the owners before beat on it pretty good I heard. I think it was the number 5 cylinder that let loose. I've heard Jeep changed the 4.0 they put in the grand Cherokee in '99 than what was used in the Cherokee. The Cherokee's 4.0s I believe are a lot more reliable. My buddy had a '98 Cherokee 4.0 and it lasted until 22?,??? Miles until it over heated. If it hadn't overheated who knows how far it could have gone...

I have no experience with the 4.7 nor do I know anyone with one(besides on this forum lol)
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Old 05-21-2012, 09:02 PM
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Re: 4.0 i6 .v.s. 4.7 v8

The big change to the 4.0 took place in the 1999 MY due to meeting tighter emissions regulations. The XJ world is filled with tons of crack heads from 1999-2001 which was part of the reason I settled on a 1998 Cherokee Classic 8 years ago. I also believe there was a change to the piston to meet emissions but cannot remember were I read it as it has been a while since I owned the XJ.

From the XJ Wiki:
Quote:
In the middle of the 1999 model year, vehicles with the 4.0 liter (242 CID) engine received a much improved intake manifold. This was done to help counteract smaller exhaust porting on the latest casting of cylinder heads, which was done to meet more stringent emissions control laws. Both the 4- and 6-cylinder engines were offered through the 2000 model year, though only the straight-six was available in 2001. For the 2000 and 2001 model years, all six-cylinder XJs received a distributorless ignition system using coil-on-plug ignition replacing the 'traditional' system previously used; coupled with better exhaust porting and the newer intake manifolds, this gave a minor increase in power over the previous models. Transmission, axle, and transfer case choices were carried over from the previous models.
More 4.0 specs here: http://www.jeep4.0performance.4mg.com/tech_specs.html
Info about the head difference from the above page
Quote:
The early '87-'90 non-HO heads have low intake ports that flow rather poorly. The later HO heads have higher intake ports that flow more air by allowing a straighter shot into the cylinders. The '91-'95 HO heads with casting no.7120 have the highest intake and exhaust port airflows, especially at lower valve lifts where it is most important, and are the best for performance. The '96-'99 0630 heads are almost identical except that they don't have a port for the coolant temp. gauge sending unit. The '00 and later HO heads with casting no.0331 have smaller exhaust ports to produce a faster warm-up of the catalytic converter and improve emissions, but performance also suffers because the ports don't flow as well as those of the 7120 and 0630 castings.
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Old 05-21-2012, 11:29 PM
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Re: 4.0 i6 .v.s. 4.7 v8

My 4.0 has a lil over 120,000 on it and runs as good as new. Most of the miles are short distance with the occasional 967+ mi. trips.
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Old 06-18-2012, 06:04 AM
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Re: 4.0 i6 .v.s. 4.7 v8

Like what was stated before, it really depends on how well it is maintained. I am not against driving a Jeep under the conditions that it was built for, but there is a major difference between using, and abusing.

I have a 4.7 HO with over 126,000 miles and it runs like a dream
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