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4.0 hype they don't make em like they used to

Interesting to follow the replies on this thread. As a guy who always just “swaps in an LS” in everything that comes my way, I was amazed by the fun I had driving my 258 powered CJ-5 home when I purchased it. A simple straight 6 and a 4 speed. It was honestly more fun than the rush of an LS! Maybe a different fun, definitely a different feeling. Driving a V8 powered Scrambler is a rush- the thing is a beast. You feel like the engine is the Jeep and you’re just strapped on for the ride. I’m sure some think “just don’t get into the gas then”- but that’s like having a full 30 round magazine and not doing a mag dump for at least the last 10 rds... that’s just not possible! After driving that CJ-5 I have had a growing yearning for something more consistent with a stock feeing Jeep. It’s hard to explain- a V8 Jeep feels “heavy” even though it’s light- it’s not “nimble” anymore. When I bought Copper it had an Iron Duke and although Highway speeds were a chore, even with 28” tires, rowing through the gears with that little engine just felt good.
Even though Red isn’t finished yet, I’m already envisioning my next project. I’m leaning towards a Jeepster Commando. Or maybe a -7. But either way I’m sticking with a smaller engine, and that has been the source of many mental builds. I also have a 2001 4.0 XJ. It has great power- still feels nimble, and cruises comfortably at speed. But it is a thirsty beast, maybe 14 on a good day. Great engine, still older technology. So what is an ideal modern replacement? A DI 4.3 out of a late model Chev van? Maybe the V6 out of a late Ram pickup? Where does the ideal combination of low maintenance, adequate power, and good economy exist? I’ve even considered diesel, but the only one smooth and quiet enough is that Banks 3.0 and thats just too much coin. I don’t want to derail this thread, but if any of you have ideas, let’s hear them!
 
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Randyzzz said:
Where does the ideal combination of low maintenance, adequate power, and good economy exist? I’ve even considered diesel, but the only one smooth and quiet enough is that Banks 2.8 and thats just too much coin. I don’t want to derail this thread, but if any of you have ideas, let’s hear them!
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Toyota or Honda turbo 4 banger. Dead reliable with almost zero maintenance. Good power and economy. But adaptability kind of sucks.
 
There is no reason a 258 powered Jeep CJ, either carburetor of fuel injected, can not run 70-80mph on the interstate.

As long as the following conditions are met:

1) tires are kept to a reasonable size (I would say 33" or smaller)
2) Gears match tire size (except 2.73 gear ratio and stock tire size, too high of gear IMO even with super small tires)
3) The Jeep is not way over weight (people, gear, bumpers, winches, add on's)
4) Expectations are realistic. You will loose some speed on hills and strong head winds. You can not effortlessly pass like you have 300 HP on tap.

Before the 258 in my red Scrambler cracked a piston skirt, I drove it countless times across this country, all climates/elevations/driving conditions. Stock 258, Mopar MPI, 33" tires, 4.10 gears, T5/AX15 transmission. It has an in cab cage, winch up front, heavy rear tire carrier/bumper, heavier fuel skid plate, rock rails. Not super fat, but heavier then stock. It maintained 75-80 mph no problem, EXCEPT some super steep/long grades in Colorado (Google "Wolf Creek Pass"), and out west one time when I was fighting constant 20-30mph head winds. Sure, I would have to down shift to 4th on some hills/grades, no big deal. Could I "effortlessly" accelerate from 65 to 100 mph? No, of course not. But I never had trouble keeping up with and passing at 70-80mph.

I drove a bone stock 1982 CJ-7 Jamboree from Colorado back to Louisiana. Stock tires, 3.31 gears, T5, bone stock carburetor equipped 258. No problems at all maintaining 70-75mph.

I drove my current "red Scrambler" from Indiana back to Mississippi. At the time, "nuttered 258", T176, 3.31 gears, 32" tires. I drove it back home 70-75mph. The 32" tires are a hair big for 3.31 IMO on some of the longer grades, but it still did OK in the hills. 3.54-3.73 with 32" tires and no over drive would be better IMO.

My green Scrambler has a rebuilt 258 (bored 40 over, mild RV cam), 31" tires, 3.31 gears, and a T5. It will maintain 70-75mph, BUT the 3.31 gears are a hair high IMO. I will probably install 3.54 or3.73 gears in the future. More personal choice, I would rather have a hair too much gear.

My bone stock 1985 Spring Special CJ7 (stock tires, 3.31, T5, stock 258 with 100% all stock computer controlled carburetor/timing, ALL emissions in place (including Cat, pulse air system) will happily cruise at 70mph all day long. With a soft top and soft doors, it gets old real quick, though!!

I sold my 1984 Scrambler, which I also drove cross country multiple times. It had a stock/new TBI 350, 700r4, 33" tires, 4.10 gears. It obviously had more power at interstate speeds, could maintain hills/grades better, and pass easier at high speeds. That being said, that additional power came with a cost of increased fuel consumption and heat. Sure, that set up was probably "better" for long highway trips, but I had no problem selling that vehicle and keeping my 6 cylinder powered Jeeps.

Expectations, gearing, tire size, must all be kept in check. 300 plus horsepower enables you to gloss over a bunch of "sins".
 
BDCCLARK said:
I never understand the whole modern engine theory. I drive a 1996 12 valve cummins truck and generally shift between 2000 and 2500 rpms. I also drive a 1989 and 1985 suburban. One is tbi and the other carbureted. They are both 700r4 trucks, but I feel like I drive them the same as my diesel. I feel like these are modern engines.
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I agree with that, calling something modern can be painting with a broad brush. Laughably I almost consider my 89 TBI 4.3/700r4 "modern". Suppose its mainly drivability of the EFI. But, comparing my 4.3 to my LMM Duramax in highway driving isn't a fair comparison. I suppose most use modern as a simple way of saying abundant power. I had an 89 Suburban with a TBI 350 and it was one of my favorite vehicles. Still miss it 15 years later.

I do agree with Randy as he stated above. I do miss the grunt and exhaust note of the I6. I miss the nostalgia of rowing gears. But I also like to get in and start the engine with my feet on the floor, knock it into drive and head down the road.

My idea of an ideal swap (possibly next version of my 8) would be a 2014+ ecotec 4.3 and a 6L80. 285 hp, 305 tq with the 4.0:1 first gear of the 6l80.
 
I guess by “modern” I’m thinking no distributor or timing to set and associated parts to maintain, definitely no carburetor, minimum 1HP per cubic inch, and capable of 18-20 mpg on the original platform it’s installed in. Turn the key and go.

Ford really seemed to hit on the magic combo with its Ecoboost line. But, in typical Ford fashion, they are anything but compact, and have miles of plumbing.


The GM Ecotec 4.3 with the 6L80E does sound about perfect. I do like a manual, though- I just don’t know if my ankle could handle it long term.
 
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When I was researching engine options, I recall that the 4.2L Jeep engine weighed about the same as an iron block LS with aluminum heads. I believe the drivetrain I am using will weight about the same as the one I removed.

232 I-6, T-5, D300 to L92 (aluminum), NV4500, NP241C.

But the weight bias will move towards the center of the Jeep.
 
ag4ever said:
When I was researching engine options, I recall that the 4.2L Jeep engine weighed about the same as an iron block LS with aluminum heads. I believe the drivetrain I am using will weight about the same as the one I removed.

232 I-6, T-5, D300 to L92 (aluminum), NV4500, NP241C.

But the weight bias will move towards the center of the Jeep.
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So technically it will handle better. 👍🏻
 
spankrjs said:
There is no reason a 258 powered Jeep CJ, either carburetor of fuel injected, can not run 70-80mph on the interstate.

As long as the following conditions are met:

1) tires are kept to a reasonable size (I would say 33" or smaller)
2) Gears match tire size (except 2.73 gear ratio and stock tire size, too high of gear IMO even with super small tires)
3) The Jeep is not way over weight (people, gear, bumpers, winches, add on's)
4) Expectations are realistic. You will loose some speed on hills and strong head winds. You can not effortlessly pass like you have 300 HP on tap.
Click to expand...

I will be running 4.56s with 35s so I'm covered there.

I want the ability to tow a small trailer for camping like a pickup bed trailer with a topper.

I have driven 12 valve cummins trucks for twenty years and I'm a bit biased in that I have zero appreciation for the wind slowing me down.

As much as I would love to have my jeep stay inline 6, I think the answer for my cumulative desires take it past it's ability's.

Chris
 
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