Jeep: give us a new power plant!

[legacy_etu]

I live in Las Cruces. Drove it back from Rosenburg, TX last month and averaged right around 19 mpg on 35’s. Since I’ve had it I’ve averaged anywhere from 20 to 17 mpg depending on how hard I was flogging it and what I’m carrying. Getting ready to go on a multi state western trip at the end of the week. Fully expecting it to do better than that dog of a Tacoma I was driving before on 33’s.

Impossible. Everyone knows the Tacoma is the bestest!!

Funny, I was visiting a good friend this past week and he was recounting his adventures with his Tundra. He had to have his entire frame replaced and a bunch or brake lines, rotors , etc because they were rotten. Unbelievable.

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[869 KPH]

(...) missing a lot of body metal, (...)

We call that weight reduction where I come from. You guys ever watch Vice Grip Garage on YT? Solid channel.

 

[ShadowsPapa]

LOL at this thread.

A JL or JT with ANY engine option available will dust a CJ like a coffee table. It's not even a contest. Not even close.

And, today's Jeep doesn't have a carb to fight with on cold mornings or when off-camber in the woods.

I miss the engines of the 1980s exactly zero.

You mean early 80s, correct? 86 saw the INJECTED 4.0
But still - I know what your point is. You can get more from less these days.

I'd love to have someone drive my JT for me and race it against my 4.0 powered Eagle.
I'm curious - I have no expectations - just really curious to see how a mild build 4.0 would do.
And if I put the experimental aluminum head on it and raised the compression even more than I already have.......... do it again.

Your "off-camber" bit is exactly why many Jeep folks put the Motorcraft carb on the 4.2 - those things would handle being tilted a lot more than the BBD ever could.

 

[ShadowsPapa]

Come on, you know you miss the smell of starting fluid at -10, the way that starter cable is just about to become transparent from the heat. Admit it, in some weird way you miss sticky secondaries that flood open after hanging up, making even the most mundane drive anywhere feel like outlaw drags.

The only reason my CJ had any scoot was it weighed very little, 2 seats, no top, missing a lot of body metal, heater was removed, no AC, no crash safety... engine was the heaviest part. It was loud, hot/cold, drafty and stank of gasoline and gear oil. No one ever wanted to ride in it and even the troopers stayed away, one told me one day he'd be afraid to look to close; run out of citation slips before running out of citations. We laughed!




High waisted mom jeans, you remember the ones; buttoned just about to the collar.

The 90's were a rough time as well, body suits under skirts and tops, combat boots laced to the knee, all the bracelets and hair bands, all covered in a trench coat and the guys looked just like the gals making night interception missions iffy.

Youse guys had to use starter fluid? I only did that at 20 below with my diesel tractors. My engines would start right up.
I guess I was the only one who actually had zero troubles with my vehicles.
My Gremlin, my AMX, my 70 Chevy with quadrajet, any of them, 20-25 below, go out and they'd start.
I have a can of starter fluid on the shelf from the 1980s - I'd used it on my tractors, and as a semi-hoarder, it's rusty, likely no longer sprays - I guess I keep it to remind me of the farm days or something.

The 80s sucked musically........luckily disco was disappearing but then it was replaced with electronic dance music. Ugh. No creativity, no great stars (or few)

 

[WXman]

You mean early 80s, correct? 86 saw the INJECTED 4.0
But still - I know what your point is. You can get more from less these days.

I'd love to have someone drive my JT for me and race it against my 4.0 powered Eagle.
I'm curious - I have no expectations - just really curious to see how a mild build 4.0 would do.
And if I put the experimental aluminum head on it and raised the compression even more than I already have.......... do it again.

Your "off-camber" bit is exactly why many Jeep folks put the Motorcraft carb on the 4.2 - those things would handle being tilted a lot more than the BBD ever could.

Honestly, take your pick. I had a couple of the injected 4.0 engines that I wouldn't piss on if they were on fire too. They leak oil like seives, make no power, and drink fuel. Sure, they had a strong torque curve down low, but peak was still <230 lb/ft. They're heavy too. I consider the 4.0 engines to be great boat anchors.

The 304 V8... sigh... well, those wouldn't get out of their own way but to be fair the 70s "oil crisis" and resulting changes to emissions pretty much neutered ALL V8 engines, so the 304 had good company.

I just can't imagine anybody wanting to go back to those days. A 2021 Jeep with 3.6L P-star will run 0-60 under 7 seconds, get excellent fuel economy, and has a torque curve as flat as a Kansas highway. Excellent for every condition or use. And if 270ish lb/ft isn't enough for a guy, there is always the crank-twisting EcoDiesel.

I thoroughly enjoy watching Dennis Collins restore the old CJ-5, 7, and 8s. Pure joy to watch. But I wouldn't trade my JT for a CJ even if there was $20k sitting on the hood of the CJ.

 

[ACAD_Cowboy]

Youse guys had to use starter fluid? I only did that at 20 below with my diesel tractors. My engines would start right up.
I guess I was the only one who actually had zero troubles with my vehicles.
My Gremlin, my AMX, my 70 Chevy with quadrajet, any of them, 20-25 below, go out and they'd start.
I have a can of starter fluid on the shelf from the 1980s - I'd used it on my tractors, and as a semi-hoarder, it's rusty, likely no longer sprays - I guess I keep it to remind me of the farm days or something.

The 80s sucked musically........luckily disco was disappearing but then it was replaced with electronic dance music. Ugh. No creativity, no great stars (or few)

My 258 had an offy intake and growth stunted holley 4bbl, rumor has it there was a hot(ter?) cam in it too. Choke = Joke In the real cold it needed a shot of fuel and starter fluid to catch but one running wouldn't quit. More than a few times I found it full of snow, like need to shovel out the pedal box to get to work. My JK has never not started even after being cold soaked for 3 days straight and mounded in snow. Despite me telling the guys the keys are in it, no one moved it, they just plowed around it. I need to use the FEL to make a hole to get it out. My own guys...

But I would take the 3.6 over any of my old engines except the germans, but that's because they were basically today's modern engines then.

I think the 5.7 would be a good balance of power and reject heat. A stomping 392 is fun but I think a smaller higher winding unit would serve us better.

 

[AstroZombie]

Yeah, I get that the Pentastar works well for a lot of people. But load up your truck, and then come to Colorado and drive up any dirt road that goes to a trailhead at elevation (between 8,000 - 10,000 feet). All those roads are steep, and you won't be able to shift out of first gear in a manual. Not enough torque at low rpms. I've only driven the auto on a test drive down at 5,500 feet, so I don't know how it performs driving uphill at 10,000 feet. Glad you are happy with your truck!

P.S. I live at 8,500 feet

You haven't lived until you've driven a 2.5l Wrangler in 3rd gear going 45 mph trying to make the uphill drive. HAHAHA, 7000 feet elevation. And my 4.0 TJ really struggled too that high. I dont see my Gladiator struggling as much as my 04 Tacoma did in big bear or even Zion loaded with 30,000 worth of E-bikes.
I bet that CJ got 8 MPG too HAHAHA and could carry anything more that a backpack and a small cooler.

I don't see it being a deal breaker.

 

[ACAD_Cowboy]

Iron Duke trying to hold highway speed... the horror.

 

[ShadowsPapa]

Honestly, take your pick. I had a couple of the injected 4.0 engines that I wouldn't piss on if they were on fire too. They leak oil like seives, make no power, and drink fuel. Sure, they had a strong torque curve down low, but peak was still <230 lb/ft. They're heavy too. I consider the 4.0 engines to be great boat anchors.

The 304 V8... sigh... well, those wouldn't get out of their own way but to be fair the 70s "oil crisis" and resulting changes to emissions pretty much neutered ALL V8 engines, so the 304 had good company.

I just can't imagine anybody wanting to go back to those days. A 2021 Jeep with 3.6L P-star will run 0-60 under 7 seconds, get excellent fuel economy, and has a torque curve as flat as a Kansas highway. Excellent for every condition or use. And if 270ish lb/ft isn't enough for a guy, there is always the crank-twisting EcoDiesel.

I thoroughly enjoy watching Dennis Collins restore the old CJ-5, 7, and 8s. Pure joy to watch. But I wouldn't trade my JT for a CJ even if there was $20k sitting on the hood of the CJ.

I don't want to go back to those days - but I guess I'm confused by the "leaks oil" and other comments I see.
I could list all of the 4.0s I've had and still have - not a one of them leaks. The only one that ever leaked was the WJ I bought from Dad's estate - and he had that fixed at 110,000 when the pan gasket started leaking. Imagine, going 100,000 miles without oil leaks. The gaskets on the 4.0 are really good, better than any other I6 I've worked on.

I guess my luck is better than most!

But that's not saying I'd advocate to go back to engines of that era and/or put it in a JT.
But for me, I'd take an old Jeep with a 4.0 as a fun daily driver. My SX4 is often used as a d-d and it's got a LEAK FREE, economical 4.0 that gets in the mid-20s mpg on speed limits of 60-65 and lower 20s when messing around town or I decide to drive it FAST. But then even the SX4 is sort of a brick going down the highway.

 

[ShadowsPapa]

Iron Duke trying to hold highway speed... the horror.

My son had one - it couldn't get out of its own way but was a decent commuter vehicle for him. It was reliable - set the choke, hit the key and it was running. He said 20 seconds later he could drive off and it didn't even protest. At the end of the day, 0 degrees in the parking lot, set the choke once, hit the key and it was running. But then I'm the one that rebuilt the engine at 100,000 miles (rings and bearings were GONE) and put a NOS carb on it.
It was an exercise in patience, though, trying to merge into heavy traffic. The thing was on valium or something.

 

[ACAD_Cowboy]

I found it to be a very soft engine overall but it required you to wring all the rpm's out of each gear. I want to blame that horrid transmission more than anything else but the combo was not unlike trying to offroad a VW, lot of throttle and lots of clutch but almost no slipping; all binary. About the3 best thing that 151 did for me was donate it's GM HEI to the 258.

 

[ShadowsPapa]

My 258 had an offy intake and growth stunted holley 4bbl, rumor has it there was a hot(ter?) cam in it too. Choke = Joke In the real cold it needed a shot of fuel and starter fluid to catch but one running wouldn't quit. More than a few times I found it full of snow, like need to shovel out the pedal box to get to work. My JK has never not started even after being cold soaked for 3 days straight and mounded in snow. Despite me telling the guys the keys are in it, no one moved it, they just plowed around it. I need to use the FEL to make a hole to get it out. My own guys...

But I would take the 3.6 over any of my old engines except the germans, but that's because they were basically today's modern engines then.

I think the 5.7 would be a good balance of power and reject heat. A stomping 392 is fun but I think a smaller higher winding unit would serve us better.

I truly appreciate the 3.6 I'd not mind if it was just a LITTLE more beefy or had more low end grunt, but it's not a game stopper either. If someone dropped a turbo for it in my lap, I'd say, sure, I'd love that for towing, but otherwise, I don't care to go backwards.

The truck below had the 4.0. My only complaint was the idle was rough at times - the RENIX system was far from perfect. No leaks, plenty of towing power. I towed grain wagons and anhydrous tanks through fields with it and hauled fuel to tractors when needed.

Again, loved those engines, reliable, simple, always started when I needed them to, never a leak, never any problems all over the country, including through fields and blizzards that stopped the 18-wheelers, but.......... I'm not about to yank the 3.6 in favor of something even based on these engines.
I have my fond memories of them, and I even still have a couple of them around - including a 401, 343, two 360s, a 258 and likely enough parts to build another, and two 4.0s.

This car below had a 258 (4.2) and 4 speed. Drove it all over the place. Was my daily driver for years - up to almost 90,000 miles. It was up Pike's Peak, all over Denver, Colorado Springs and other mountain areas. Never skipped a beat, never leaked, never failed to start any time.
Pic taken in 1980, Colorado

Tough engine, basically the 4.0 was a truck engine. They even sounded like truck engines according to some people. But the RENIX electronics and fuel injection left a lot to be desired over-all as a system.

No leaks here, purrs like a kitten, starts when I want, decent mileage (mid-20s, depending on speeds, otherwise lower 20s, I have achieved 27 mpg with one tank)

 

[WXman]

I have never been under the hood of ANY 4.0L I-6 that didn't have oil at least seeping from between the block and head, if not also the valve cover and crank seal.

As far as the OP talking about weight... yes today's Jeeps are much heavier but that's because they're much safer. Have a crash in a CJ and you're pretty much a dead man.

 

[Wheelin98TJ]

I don't want to go back to those days - but I guess I'm confused by the "leaks oil" and other comments I see.
I could list all of the 4.0s I've had and still have - not a one of them leaks. The only one that ever leaked was the WJ I bought from Dad's estate - and he had that fixed at 110,000 when the pan gasket started leaking. Imagine, going 100,000 miles without oil leaks. The gaskets on the 4.0 are really good, better than any other I6 I've worked on.

I guess my luck is better than most!

But that's not saying I'd advocate to go back to engines of that era and/or put it in a JT.
But for me, I'd take an old Jeep with a 4.0 as a fun daily driver. My SX4 is often used as a d-d and it's got a LEAK FREE, economical 4.0 that gets in the mid-20s mpg on speed limits of 60-65 and lower 20s when messing around town or I decide to drive it FAST. But then even the SX4 is sort of a brick going down the highway.

RMS leak is common for the 4.0.

 

[DAVECS1]

I/E ratio and burn capability is the key. Nothing earlier than 97 stock had the iron to create the power densities we see today. Some engines with modern aftermarket heads and their geometries have the capability to become serious power houses. The Dodge 360 stroked to 402 with ported edlebrock heads can pump out the jams. Todays engines just burn fuel amazingly and the controls then take it to the next level. The 3.6L runs at stoich 90% of the time, it is so efficient it can use an enrichment of .2 to accelerate pretty aggressively. That is part of the reason the SC folks struggle. Unlike older engine that dip into the 12:1 afr while accelerating to make power. The 3.6 dips to 14.5:1! Don't get me wrong I love bringing old engine to life to make them compete with todays uninspired computer junk

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