Everytime...

"HammerheadFistpunch" (hammerheadfistpunch) 02/12/2014 at 12:49 • Filed to: cruisin'

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...someone mentions how great the 4.0 AMC/Jeep Powertech I6 engine is I think of this.

This is the Toyota 1FZ-FE, and let me say that I'm not saying that the 4.0 isn't a great engine (it is) but given its 4.0 liters of displacement and that it makes its peak torque (225 ft-lbs) at 3000 rpms, I look at this chart at see that same torque figure (225 ft-lbs) is available at...oh...idle. Not bad for an extra 500 cc of displacement. I should also say that im not diminishing the greatness of the AMC engine, only that I feel a little sad that this engine never gets remember in the annuls of automotive greatness along side the AMC...by virtue of sheer number built I suspect.

The 1fz-fe wasn't produced for many years because the vehicle it was meant for just got too big and heavy for an I6 so it went to a V8 just 5 short years after is was introduced (though it continued to be produced in other markets until 2005 and in forklifts in carburated and LPG forms to this day). It is generally regarded (aside from an issue with the head gasket) as the most durable gasoline engine ever built. Given that mine is on mile 240,000 and running like a top and many are doing 300,000+ without issues (or re-build) I'd say they may be right. It was designed to be rebuilt 3 times (with bore work, more without) and many people who tear them down, even at 300,000, to do the head gasket (an issue with 90's materials) find that the bottom end is in perfect condition, and not in need of work at all.

If you want to read more on the engineering and history of this amazing engine, there is a good writeup !!!error: Indecipherable SUB-paragraph formatting!!!

The only downside to this engine is that its saddled exclusively to an SUV with permanent 4wd that weighs, stock, more than 5000 lbs vs the XJ which got 2wd and weighed ~3200 lbs. The jeep has better performance to be sure, but most of that was the weight. I'm still blown away with the idea that at ~1200 rpm (where my torque converter starts really holding) I'm producing more torque than the amazing 4.0 powertech did at its peak.

You feel it when you are off-roading or carrying a load. I've discovered it really doesn't matter how much weight you put in the truck, it will get the same mileage and drive the same. I've loaded mine up with ~1500 lbs and still got the best mileage I can hope to get on the freeway, and couldn't tell (aside from braking) that I was even carrying extra weight.

Torque: its not how fast you can do it, its how much you can take with you.

Also - I know I'm totally overplaying the cruiser hand of mine. Don't care. Okay, I do, I will try and ease off.

RamblinRover Luxury-Yacht > HammerheadFistpunch 02/12/2014 at 13:07

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Boy, I'll tell ye summat, where I comes from we'm don't be havin' none o' this crossflow head nonsense. We'm installing an F-head six, and if'n it don't be enough at 86 horse for 2.6, we just be dealin' wiv it. Arn't no kind of poofter needs more'n 2 valves a cyl, eh?

Party-vi > HammerheadFistpunch 02/12/2014 at 13:08

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JEEP GUY POST

The 1FZ churns out torque at low RPMs because it's an undersquare engine; longer stroke than bore means more torque at lower engine speeds. The 4.0L is an oversquare engine, so torque comes in at a higher RPM. We're almost comparing apples to oranges here but the 1FZ is definitely the better engine for torque.

Not to take anything away from the 1FZ (it's a damn good engine) but a Jeep inline-6 engine with similar displacement will make more power (granted they never did stock and all these engines have been modified by owners/the aftermarket but this is the only way I can win here so :P). A 4.6L Jeep engine (4.0L block, 4.2L crank) will make 250-260hp and around 300lb-ft of torque, but peak torque is still made around 3,500-4,500rpm. This is without the benefit of DOHC or high-lift head design (at least that was the case on my stroker engine).

Also, the 1FZ is a more technically advanced engine (crossflow head, DOHC, etc.) and the Jeep engine was designed by AMC on a budget. I remember my 4.0L had 288k miles on it and refused to die. As far as a stock motor goes, the 1FZ-FE is likely the better choice of the two, but the 4.0L is still a good platform.

/Jeep rant over

HammerheadFistpunch > Party-vi 02/12/2014 at 13:14

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no question the 4.0 is a great platform and it certainly can be tuned to make great power so taking nothing away from the 4.0.

I've been toying with the idea of a compression bump on mine to put me up into the 240's in hp and 300's in torque when I do my HG. It's not like Its going to need to run on that cheap Sub Saharan gas in Utah anyway, why not get a little extra out of it. maybe even a port and polish too, why not?

Party-vi > HammerheadFistpunch 02/12/2014 at 13:17

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I'm not sure what a P&P would get you but a compression bump would definitely help. I'm assuming your engine can detect knock and adjust timing accordingly.

HammerheadFistpunch > Party-vi 02/12/2014 at 13:25

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yes, it has 2 knock sensors. A p&p is for the hp, the flow is great at low rpm, but poor at higher rpms.

MD0811 > Party-vi 08/30/2016 at 22:05

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Actually the bore of the 1FZ is 100mm and the stroke is 95mm so it is also oversquare. Yes I realize your comment is two years old lol