I6 or V8 ?

[tlowery04]

for daily driving and moderate off roading which engine is better? the I6 or the V8 and why?

[Ristow]

both fine. if you have a V8 rig,keep it.likewise,i wouldn't go through the effort of converting an I6 rig to an 8,the I6 is a great engine design,and AMCs' family of I6s' are particularly good.

there is a few relatively easy things you can do to the 258 I6 to get some pretty impressive power from it.

[Brown Bear]

Run what ya brung. Wouldn't do any trading for either unless I was in a bad way.

[Stuka]

Each has its own advantages. A stock 258 i6 has more low end torque than a stock AMC 360 V8. But once you get up in rpm a bit, the V8 is going to have a whole lot more HP. Having wheeled with both, I really think I prefer the i6's grunt. Being I have manuals, the i6 seemed harder to stall to me.

But beyond that, the i6 is a more reliable, longer lasting engine. But as mentioned above, I dont think its worth swapping one for the other unless you need a new engine anyway. If I ever swapped my i6 for anything, it would be a 4BT diesel.

[joe]

I'm a big fan of the AMC I6 in either Wag or truck especially w/man trans but if you need to haul heavy loads often or tow with the truck the V8 is nicer.
As the others have said which ever you have it isn't worth it to swap to the other unless you need to.

[mdill]

The I6 has the edge in aftermarket support and can be built pretty stout, the thickness of you wallet is about the only limit. (al kinds of fun stuff off the shelf to build everything from a 4.6+L EFI blown with alloy heads, to just a mild carbed setup)
The V8 has cubes, but you have to bring a thicker wallet to build it much past stock, not near the support the six has, but check out Bulltear, MC does some cool stuff)

Personally I would run what was in the hole to start with, and build from there, Jeep did to many odd things between the I6 and V8 rigs to make a swap easy.

Mike D.

[710 Burner]

for daily driving and moderate off roading which engine is better? the I6 or the V8 and why?
For your purposes, what Stuka says is very true of any I-6. More low end torque, and generally slightly better fuel economy. I tow campers and boats with mine, so I prefer the V-8 for that purpose. If I were strictly driving and off-roading, I would prefer the I-6. I must say the 360 holds its own off road though, but I have the tow package gears.

[Stuka]

There are a lot of things a V8 is better for offroad. For mudding, its all HP, so low end torque is pointless. For a lot of more extreme wheeling types, you also need power. Although a supercharged i6 can pull pretty good. I am speaking mostly of trail riding. The i6 will get way better milage offroad, and quite a bit better onroad (I never got over 14 in the cherokee, but got 17 in the J10 with a 258)

[Kali]

my 82 j-10 is an automatic with the I-6 and 4.10 gears. its gets around just fine, but my 88 waggy with the 360 and 3.31 gears has more get-up-and-go.
if i had the choice my 82 would have a 360 or 401 in it, or at the very least a well built I-6.
i think the 1982 258 had somewhere around 115hp and 210torque from the factory... in my opinion that is an underpowered engine for these trucks. but then again im just a young kid and i like to fly around like im driving a porsche :thumbsup:

[shimniok]

For FSJ I think the I-6 is going to be underpowered, depending on altitude. Up here in the thin air, trying to pull a 10k ft pass is hard enough with a 360 let alone with a lower power I-6. I think it's valid to swap in a V8 if you're after more power.

I suspect the I-6's appear put out more low rpm torque for two reasons, first the gearing is set up lower (torque multiplication) because the engine, itself, is so light on power and second, the motor is probably set up more for low end torque than high end hp anyway. Given the oem technology, power is more about cid and cam.

I found a website that cites 210 lbs-ft @ 2000 for 258cid -- very low and an indicator of a very short duration cam and other tuning to focus all the power in the lowest rpm range. So the question then is, does a 360 produce more torque at 2000 rpm? Don't know but I have a hard time believing it doesn't. The same page quotes 295 @ 2600.

If you have enough air where you live the 6 is probably great. Up here, you'll always be wanting more power... sometimes even with a 360!

Michael

[Stuka]

For FSJ I think the I-6 is going to be underpowered, depending on altitude. Up here in the thin air, trying to pull a 10k ft pass is hard enough with a 360 let alone with a lower power I-6. I think it's valid to swap in a V8 if you're after more power.

I suspect the I-6's appear put out more low rpm torque for two reasons, first the gearing is set up lower (torque multiplication) because the engine, itself, is so light on power and second, the motor is probably set up more for low end torque than high end hp anyway. Given the oem technology, power is more about cid and cam.

I found a website that cites 210 lbs-ft @ 2000 for 258cid -- very low and an indicator of a very short duration cam and other tuning to focus all the power in the lowest rpm range. So the question then is, does a 360 produce more torque at 2000 rpm? Don't know but I have a hard time believing it doesn't. The same page quotes 295 @ 2600.

If you have enough air where you live the 6 is probably great. Up here, you'll always be wanting more power... sometimes even with a 360!

Michael

1: 258's always got the same gearing as V8's. They never got lower gearing.
2: If you look at dyno sheets, the torque curve of a 258 is basically flat, they have almost the same amount of torque at 700rpm as they have at 2000rpm. The 360 has less torque at idle. Its not so much to do with cam as it is to do with engine design as well. An i6 has a much heavier crank being that its a lot longer. This creates more rotating mass, which makes the engine harder to stall, which is why they fel like they have so much grunt compared to a V8. My Cherokee (with better gearing) was easier to stall with its 360/T18 than my J10 with its 258/T176.
3: I have driven my J10 to 10k feet WITH 2.73 gears and while lacking power for sure, it made it.

Driving with a 258 is like driving a diesel. Everything is below 3k rpm. You can build them to produce power higher up, but fromt he factory is most all low end. And as anybody knows, torque gets a vehicle moving, not horse power. Now if you are doing a type of offroading that requires high horse power like I mentioned above, than a V8 is the way to go (unless you instead turbo or super charge the i6, which will give you the same power, but with a stronger engine. Not to mention up at 10k feet the i6 will run circles around an NA V8). If all you do is trail riding, than a 258 will be fine. My J10 current has 34" tires with 2.73 gears, and its actually drivable with its close ratio 4sp. Although I will be happy come this week when I put the 4.56's in.

Just curious, have you ever driven an FSJ with a 258? Its an easy engine to get power out of with a few bolt ons. Lot of dyno sheets showing guys have 200hp and 350ish ft lbs of torque with just puting in a cam, 4.0 head, good carb or efi, and in some cases stroking them up to a 4.6L.

[Locked and Loaded]

258 is good with a MANual (manly) transmission. If you have an automatic(God created for women and smokers) than go with the 360. Has anyone had a problem with vaporlock with a 258?

[Stuka]

258 is good with a MANual (manly) transmission. If you have an automatic(God created for women and smokers) than go with the 360. Has anyone had a problem with vaporlock with a 258?

I have never had vapor lock on my 258, I have on the cherokee before though. But the 258 runs noticably cooler than the 360 also. Its got a LOT of mass for a 6 cylinder.

[710 Burner]

I thought I read on here somewhere that the late model 360 like mine produced less torque than my 03 TJ did with the 4.0. It was IIRC 195 ft/lbs on the TJ. I will have to search on that.

[Stuka]

I thought I read on here somewhere that the late model 360 like mine produced less torque than my 03 TJ did with the 4.0. It was IIRC 195 ft/lbs on the TJ. I will have to search on that.

That 4.0 makes 190hp @4600rpm and 235ftlbs of torque @2300rpm. Which is more power than the ~154hp 360 used in the 80's.

[H Callaway]

Give me a bottom of the heap little I-6 in my Jeep! :) Kind of rhymes.
The 6 gives you more room in the engine compartment and two less spark plugs to change. Now a 401 V-8 is a different story. I got to see a Gremlin X 401 Conversion today at a car show. It really filled the engine compartment. It would have looked good in my Thriftside.
http://www.fsjworld.com/gallery/hcallaway/90569.jpg

[TexTJ209]

I thought I read on here somewhere that the late model 360 like mine produced less torque than my 03 TJ did with the 4.0. It was IIRC 195 ft/lbs on the TJ. I will have to search on that.


Yeah, they'd pretty much emissions raped the 360s by the 80s.

[londonhogfan]

So what kind of performance upgrades would be suggested on a I6?

[Ristow]

4.0 head. clifford or offy intake. cam.

[tlowery04]

how well do the two engines stack up at an elevation of 6910 ft. I live in flagstaff and am not considering switching engines out so much as which truck to get.


Thanks


Trent

[shimniok]

2: ... An i6 has a much heavier crank being that its a lot longer. This creates more rotating mass, which makes the engine harder to stall, which is why they fel like they have so much grunt compared to a V8. ...

Very interesting...

3: I have driven my J10 to 10k feet WITH 2.73 gears and while lacking power for sure, it made it.

I'm sure. Was it able to keep up with traffic or was it in the super slow lane, middle lane, passing like a rocket in fast lane? :D

Just curious, have you ever driven an FSJ with a 258? Its an easy engine to get power out of with a few bolt ons. Lot of dyno sheets showing guys have 200hp and 350ish ft lbs of torque with just puting in a cam, 4.0 head, good carb or efi, and in some cases stroking them up to a 4.6L.

If you live at altitude forced induction rules. It sounds to me like the I-6 is superior behind a manual for off-road and can be built up. If you want even more hwy power or hp for mudding(?) either blower/turbo or 360/401. If you have auto trans, V8 is the way to roll.

Michael

[fulsizjeep]

In 1988 & 89, I had a 84 GW with 258 with auto and 2.73 gears, all stock. It was a beauty, a good runner and the only vehicle I ever paid more than $10,000 for. This was near sea level on mostly flat land in FL. It was a great family truckster which it was bought for. I drove it to the races at Daytona both years and camped in the back at the infield. We made one trip to So TX in it too. The gas mileage was usually around 18 on the highway.

Now in the mountains here, I would think that same FSJ would be having a stroke on the climbs. We live at 6900 feet and run mountains over 10000 feet but mostly between 7000 and 9000. The 401s do very well with that environment. ;)

[Stuka]

Yeah, a 258 with an auto trans is hurting bad on hills. They can't take a 25% power loss from the auto trans and still have enough to really pull.

As for the 10k foot pass we have here, its not a freeway. Its a tight, twisty, and very steep (26% grade in some spots) road that was cut over the mountains about 100 years ago.