Convert I6 or V8 to 4 Banger or quit wheeling... - JeepForum.com
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post #1 of 30 Old 05-16-2008, 07:44 AM Thread Starter
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Convert I6 or V8 to 4 Banger or quit wheeling...

The day after filling up my reasonably economical Frontier (18-22 mpg) for 75.79, I am thinking about the CJ and my plans of swapping in a 5.0 HO or hotrodded 258 and it just seems like a bad idea.

If you had to do a 4-banger conversion to keep your Jeep, what motors would you be looking at?

In my case with a GM bellhousing Pontiac and Chevy would be the obvious choices. But thinking outside the box, what would you be looking at for excellent mileage and decent power?

Keep an open mind, I am not suggesting that guy's running 35"-38" tires are in this group, but there are a hellavu lot of people who are mild four-wheelers and would go this route.


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post #2 of 30 Old 05-16-2008, 08:05 AM
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Just my .02, I personally own a 4cyl CJ and it is no more economical than my 6 cyl YJ, or my 8 cyl Ford Expedition. I believe it has to do with your basically driving a shoebox through the air, a good amount of drag is being created.

Better to have Jeeped & Rolled Over then to never have Rolled Over.
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post #3 of 30 Old 05-16-2008, 08:12 AM Thread Starter
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joemac...

Think outside the box... OIIIIO what modern FI 4-cylinder would make a good swap?

I think my Frontier has a similar boxy profile and certainly larger than a CJ but with more rake in the windshield. It has a 265 hp V6 and weighs around 4300 lbs but gets excellent mileage for this weight and size vehicle. I have not ventured to the Nissan board in a while but I bet the king-cab 4-cylinders are in the high 20's.

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post #4 of 30 Old 05-16-2008, 08:14 AM
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You will not get better gas mileage out of an I4 in a CJ. You may as well stick to the I6 or V8. The I4 is going to be struggling so much it will be burning as much gas or more.

Basically you will not get good gas mileage in a CJ period.

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post #5 of 30 Old 05-16-2008, 08:24 AM
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Exactly my point Sub, I have seen 8 cyl motors be very economical because they work much less than the 4, personally I like six's. The added drag and resistance I feel makes any engine work harder you might as well get one powerful enough to overcome the added energy needed.

I personally don't believe a FI 4 will be any better for economy. The 6 cyl in my YJ is FI and gets about 16 -18 MPG. The 8 cyl Triton in my Expedition gets 12 City/16-18 Highway with a vehilce that weighs twice as much or more than my YJ.

I am thinking if you took a FI 4 cyl lets say from a 90's vintage Dodge Neon which gets about 40 MPG and through it in the Jeep I think the MPG would go down dramtically.

I work in IT (computers, servers and those tech things), so I am no way a mechanic or engineer and I only formed these opinions from what I have and drive.

Better to have Jeeped & Rolled Over then to never have Rolled Over.
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post #6 of 30 Old 05-16-2008, 08:28 AM
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What about the cost to do the swap? If you had to change motors, drivelines, etc etc etc. How long would it take you to re-coup this cost by saving a couple of dollars each time at the pump? I'm just saying what's the cost of 'what if'?

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post #7 of 30 Old 05-16-2008, 09:54 AM
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Another problem is that these newer I4 motors are made for horsepower and not as much torque, and a lot of them are much higher revving engines. My V6 DD cruises at 3k RPM, my 258 I6 absolutely screams at 3k. That's just the difference of having a motor made for low-end torque. You will also find that those newer I4 motors are going to have a terrible torque curve, so you'll get flat spots while accelerating. Heck, even the JK has a flat spot in its acceleration with their minivan V6. You will find yourself having to run 4.56 or taller gears to even be able to accelerate with those motors. The newer I4 motors are also going to be aluminum block and head most likely. Overheat that thing and it will literally explode. I've nearly overheated my I6 3 times now due to busted radiators/fans and haven't even busted a head gasket.

All that, and you are still going to get horrible gas mileage. It doesn't kill me to fill my CJ with gas even though it only gets about 12-13mpg. You just have to love your CJ and that I do. If you want to play, you have to pay... and man is it worth it!

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post #8 of 30 Old 05-16-2008, 10:32 AM Thread Starter
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A lot of "can't, won't, never..."

I would probably have the same reaction if I were born in the 80's but I'm not, and I have a mortgage, two daughters and not a lot of disposable income...therefore, I am keeping an open mind.

A coworker has a 4cyl YJ, hard top 5 speed and I was floored when he said he gets 17 around town with the AC on. I would have expected more. He's running 4.10's with 30" tires and in his 50's, not a fast driver.

Those of you who do have 4 bangers, are you lifted, geared, loaded down with gear and driving it like you hated it? Or, are we talking stock or mildly modified?

If you had to make the swap, what would engines would you consider?

Ya'll do have some good points, newer engines rev higher and make torque higher up the rpm scale. But we have seen fuel efficiency climb to unheard of levels even with heavier vehicles.

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post #9 of 30 Old 05-16-2008, 10:46 AM
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Hey 243, What gears are you running? That would be something to consider that would definitely affect mileage. That being said I run a 258 in a cj with 538s (obviously not good for highway but I won't compromise the ability offroad) and a good friend runs a 2.5 4cyl in a 94 yj he gets between 15-18 MPG, he does fine chasing me up the highway to the trail and i fill up on the way to and from the trail while he has 1/4 tank left when we get home. Hope that helps.

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post #10 of 30 Old 05-16-2008, 10:46 AM
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I threw up in my mouth a little when I read your post.



All kidding aside..... Go find an old 151 Pontiac engine and beef it up as best you can.

You will hate it, but you may get another 5 mpg.

I personally say, go the other way!

Put in a 454 big block!! That engine could pull a Jeep around at idle! You could get some serious gas mileage then!
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post #11 of 30 Old 05-16-2008, 10:52 AM
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Quote:
Originally Posted by 243 View Post
A lot of "can't, won't, never..."

I would probably have the same reaction if I were born in the 80's but I'm not, and I have a mortgage, two daughters and not a lot of disposable income...therefore, I am keeping an open mind.
Don't discount the negative reactions as you're keeping an open mind. I understand you're situation, but the facts are we're driving a four wheel drive brick. The best engine is the one that can stay in it's peak performance RPM. The heavier, less areodynamic the vehicle, the bigger the engine needs to be.

Best way to increase MPG's IMO, get tiny tires to reduce rolling resistance, install the highest gears possible, never use 4WD, keep the soft top closed at all times and maintain the engine like it's a heart machine and you're connected to it.

My 83 CJ5: I6, 31's BFG AT, T176, 2.73 gears = 18 MPG

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post #12 of 30 Old 05-16-2008, 11:00 AM
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i would say a rebuilt or good used 4.0 I6. i understand where you are coming about 4 cylinder getting good gas milage, but to a large extent that is all theoretical. i have a couple friends who have S-10s with the 2.2 in them and they see about 20 or 21, and those things have the aerodynamics of a rocketship compared to a jeep. on the other hand. a good 4.0 driven correctly has the potential to see 20 mpg, with correct gears and such.

i often try to drive behind 18 wheelers if i can, i can notice a big difference on wind drag by getting behind one, the jeep just moves alot easier.

but seriously, the 4.0 or 4.2 is really the best bet. ever thought of adding fuel injection to the motor that is in it, there are some threads in this forum about it, i think it was said to cost about 400 bucks.

one last, the number one cause of suicide in this forum is have a 4 cylinder in a jeep,
they go from 0-60 sometimes.

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post #13 of 30 Old 05-16-2008, 11:05 AM Thread Starter
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GasAxe...no problem with the neg's, I hate the thought of staying with my GM 151 like the majority but I don't live in a fantasy land either. At 44 years old I've experienced some bad situations but far less than the 50 and 60 year old guys.

The negative reaction could be due to the age bracket of Jeep owners, my WAG is that 90% are 17-30 years old.

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post #14 of 30 Old 05-16-2008, 11:18 AM Thread Starter
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bulljeeper, that last line is funny!

I may not be happy at all with the 4 cylinder but I won't know until I start driving it on a regular basis. But like any true hotrodder, I am willing to look at all swaps as candidates.

An example is the 4BT, I am a true Cummins fan after having owned two already and this was very high on my list when I was into FSJ's. It is not entirely out of the question but diesel is unlikely to ever be cheaper than gas again. Advantage, if I want to run biodiesel I have the place and time to make it now. Disadvantage, I have to go source WVO. Then we have the noise issue, I ran my Dodge for a few weeks without carpet and padding and it was deafening, it would be the same in my CJ.

In the end, a small FI V8 like the 5.0 would probably be the least compromised solution.

However, nobody has offered a suggestion for potential 4cyl swaps...Nissan, GM, Toyota???

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post #15 of 30 Old 05-16-2008, 11:39 AM
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Quote:
Originally Posted by 243 View Post
GasAxe...no problem with the neg's, I hate the thought of staying with my GM 151 like the majority but I don't live in a fantasy land either. At 44 years old I've experienced some bad situations but far less than the 50 and 60 year old guys.

The negative reaction could be due to the age bracket of Jeep owners, my WAG is that 90% are 17-30 years old.
I was born in the 60's myself, I pay a mortgage as well as feed myself, my wife and 6 kids. I have long looked into better mileage vehicles and I always come back to the added cost of said vehicle combined with how many years it takes to get a return on my money. I always come back to it's cheaper to run what I already own, not what the bank owns.

I wouldn't take what anyone is saying as negative, it is just our opinions, and I believe by posting you wanted to hear all up or down. Good luck though and keep up the research.

Better to have Jeeped & Rolled Over then to never have Rolled Over.
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