Question about engines

[Jeepmedic46]

I currently have a 4.0 in my 2000 Jeep Cherokee. I was wondering if I could rip out the computer and put in a carbureted 4.2 like I had in my YJ. In Massachusetts I only have to pass safety not emissions.

 

[Billiebob]

Someone who thinks like me. I loved the 4.2 in my YJ.
I doubt the computer will be an issue but you will need a different fuel pump and the bell housing or clutch or transmission might not mate up.

 

[MidOH]

The 4.0 is better anyways. Don't waste your time.

Grab an extra ECM and the key sensors.

 

[tjZ06]

Why not build a stroker out of the 4.0 and put a much better EFI on like something from Holley?

 

[Shakes355]

If you've got money burning a hole in your pocket and the time, sure. You do you, any way you gotta scratch the itch.

For someone with limited time and budget, I wouldn't say its advisable. Cherokees are a dime a dozen and its exponentially cheaper to fix what you got or swap your suspension and other expensive goodies over to a better running rig.

I went a similar route with a different rig and learned my lesson. Spent a lot of time, energy and money for a setup that was, in the end, no better in any way that functionally mattered.

 

[Jeepmedic46]

Why not build a stroker out of the 4.0 and put a much better EFI on like something from Holley?

I haven’t seen anything from Holley on the rail system.

 

[mmssierra]

I have ridden in a CJ5 with a built 4.2 and it felt like a V8. So I get it.

With that said,, here is an article/video on Powernation about building 4.0 to produce 242hp. They use a cam, new head, and fuel injection from Fast. Rebuilding a 4.0L Jeep Straight Six to 242HP

 

[rgallant]

I have ask why, not a jeep guy. Is that under powered, I would not think you would gain much

 

[Murphy Slaw]

I'm a fan of the 5.7 Hemi...

 

[Billiebob]

A carburetor has a certain feel to how it develops torque which is better than any EFI system. Most aftermarket EFIs are all about horsepower but torque is more valuable in a Jeep if you are wheeling and want to tread lightly. Plus a carb starts better in extreme cold.

 

[MidOH]

Not once it gums up on our new stellar BS green gas.

I haven't seen any Jeep setup that out performed the 4.0's stock fuel injection. Learn that system, it's one of the easiest fuel injection systems out there to keep running well. It'll take care of you, if you take care of it.

If you want to dump money, get a stroked long block and some bigger injectors.

 

[tjZ06]

I haven’t seen anything from Holley on the rail system.

Not sure I know what you mean by "on the rail system." But I mean a more universal EFI setup from Holley like their "sniper" line: Sniper EFI - Holley Performance Products You can run a carb-style intake on the 4.0 with one of these self-contained units. You'll still potentially need to do fuel-system work if the stock fuel pump for the factory EFI can't provide enough flow/PSI... but I suspect it'd be fine if you're not adding a ton of power.

Of course, you're still a fair amount of money into a stroker rebuild, the new EFI etc. Really, with so many parts out there to support it, why not just consider a junkyard 5.3 "LS" swap? When the 4.7 in my WJ ate some valve-seats I would have loved to just go 5.3, but it's not as straight forward in a WJ (requires cutting and sectioning the unibody, and people don't make swap headers/engine mounts/etc. like they do for an XJ) plus I live in CA. :(

It's really hard to beat a basic 5.3 with a mild cam (even just a factory '02-04 LS6 cam) for power, weight, reliability, sound etc.

-TJ

 

[Jeepmedic46]

I was thinking of the rail system over the spark plugs. I apologize for the mix up.

 

[Dilldog]

EFI is better than a carb in every way, more reliable, less maintenance, more accurate fuel metering, cleaner burning, better throttle response and the engine itself will last longer as a result of less fuel dilution of oil and less washing of the cylinder walls. Those are facts, you are taking a significant step backwards by ditching a well operating fuel injection system. Having owned and driven 4.2 and 4.0 Jeeps I honestly don't know why you wouldn't stick with the 4.0. And yes I have experience tuning and building carbed engines. Honestly the only reason to run a carb is if you are trying to stay period correct for a project, or to just get something going, as building a carbed set up is cheaper and easier.
To Add, I should say that TBI really isn't much better than a carb. My comments are specific to port fuel injection systems with one injector by cylinder.

 

[Jeepmedic46]

EFI is better than a carb in every way, more reliable, less maintenance, more accurate fuel metering, cleaner burning, better throttle response and the engine itself will last longer as a result of less fuel dilution of oil and less washing of the cylinder walls. Those are facts, you are taking a significant step backwards by ditching a well operating fuel injection system. Having owned and driven 4.2 and 4.0 Jeeps I honestly don't know why you wouldn't stick with the 4.0. And yes I have experience tuning and building carbed engines. Honestly the only reason to run a carb is if you are trying to stay period correct for a project, or to just get something going, as building a carbed set up is cheaper and easier.

I honestly am learning about all this. My YJ was great with the 4.2 I had a tj with the 4.0 and always felt that the 4.2 had more power. Do you have any recommendations on books to read to help me. Unfortunately I’m doing this late in life. I looked on the Holley site and didn’t see anything for a XJ.

 

[Dilldog]

I honestly am learning about all this. My YJ was great with the 4.2 I had a tj with the 4.0 and always felt that the 4.2 had more power. Do you have any recommendations on books to read to help me. Unfortunately I’m doing this late in life. I looked on the Holley site and didn’t see anything for a XJ.

So heres the deal, the 4.2 is quite a bit different. Their torque curve is substantially different, they make torque at about 1000rpm less if memory serves. This means it will feel more powerful. The 4.0 has a different head design that allows it to deliver more power across a broader rev range. It feels less torquey because it's delivery is more linear and it is a higher revving engine. To get the most out of the 4.0 you need to run it between 3k and 4k rpm, where as the 4.2 is happy between 2k and 3k.
At the end of the day comparing a 4.2 to a 4.0 is comparing apples and oranges. Both grow on trees but are completely different. Just like the 4.0 and 4.2 share block architecture but are very different.
As far as tuning and such I don't have much advise. I never really got into hopping up my Jeep engines as I never regarded the Jeep as a hot rod, just a good beat around utility vehicle.

 

[Smileyshaun]

As much fun as motor swaps are here’s a good rule of thumb . Sit down and figure out what it’s going to cost and how long it should take .... now double your budget and triple the time and you will be close to reality . You can get held up for a couple days just trying to track down a bolt . Even simple swaps can sometimes take forever because of small parts .

 

[KonzaLander]

I loathed the carbureted 4.2 in my YJ. It was plain awful until I did the "nutter bypass", but even after that it never impressed me. Maybe a Weber carb would have made it tolerable. My 4.0 powered Jeeps (TJ, MJ and XJ's) would all easily run circles around that 4.2 YJ.

Check out the www.jeepstrokers.com forum. While it is a site primarily geared towards building a stroker, you can use a lot of the information to build on a non stroked 4.0. I've rebuilt 2 4.0's (03 TJ and 99 XJ) and never felt to need to 'hot rod' the motors. Outside of piston and cam choice I have stayed stock since they are plenty powerful and reliable in stock form. You would probably notice some improvement getting the head rebuilt by a machine shop.

 

[smritte]

EFI is better than a carb in every way, more reliable, less maintenance, more accurate fuel metering, cleaner burning, better throttle response and the engine itself will last longer as a result of less fuel dilution of oil and less washing of the cylinder walls. Those are facts, you are taking a significant step backwards by ditching a well operating fuel injection system. Having owned and driven 4.2 and 4.0 Jeeps I honestly don't know why you wouldn't stick with the 4.0. And yes I have experience tuning and building carbed engines. Honestly the only reason to run a carb is if you are trying to stay period correct for a project, or to just get something going, as building a carbed set up is cheaper and easier.
To Add, I should say that TBI really isn't much better than a carb. My comments are specific to port fuel injection systems with one injector by cylinder.

all of this....^^^
plus fi will also start way better in extreme cold, will run the same at 0 ft or 8000 ft, fuel starvation off road is completely eliminated and drivabilty is vastly improved.
all of my vehicles have been carbed except for the two i have now. would never go back to a carb except as dilldog states, for a period correct build.
my '90 K1500 is tbi, which really is a little above a carb, but deadnuts reliable. 30 yrs, 400 00 kms with one "rebuild" which consists mostly of gaskets and seals and is easier to do than rebuilding a carb.
my '85 K30 was stock intake with a quadrajet, then a edelbrock intake and holley 750, last 18 yrs has been edelbrock port fi, and there is no comparison. with fi, i just reach in and turn the key- fires up and idles perfectly just like a newer vehicle, no throttle pumping, no choke to play with, no stalling out.
same truck, 2 carbed versions, one fi version, you'll never convince me a carb is superior...

YES
If you understand fuel, you would not ever consider a carb, especially off road. Carbs are great as long as you dont mind retuning them for elevation change and air density. OH dont take too steep of a hill or too rough of a road either. Make sure its warmed up enough so the choke comes off too.
Carbs are great if you want simple and something that sort of works.

 

[LostWoods]

I have ridden in a CJ5 with a built 4.2 and it felt like a V8. So I get it.

With that said,, here is an article/video on Powernation about building 4.0 to produce 242hp. They use a cam, new head, and fuel injection from Fast. Rebuilding a 4.0L Jeep Straight Six to 242HP

"Like a V8" in the sense that the 305 in the CJs was that anemic or like an actual V8 because those engines have never really been competitive with the 4.0L for power. Even built, you can do better with the EFI engine.