mike10114

So I have been wondering if there is any way to convert a fuel injected motor, (the bare motor, basically the block. and all contained within.) to a carbed motor.

I have been told that I can do this by swapping the Intake manifolds.
And then again I have been told by more trusted mechanics that I can not.

Since there is so much conflict in my hometown about this question I submit it to you Jeep geniuses for an answer.

Due to the fact that I hate computers in rigs and anything related to a computer controlling anything in my rig. I wanted to know if I could do this.
Computers and all of those crap sensors that come with them just break to much and easily.

I don't want to have to abandon my Jeep for a Chevy.... Even though I like both.

89Laredo

Maybe you could use the manifold from a carbed 2.5? I honestly dont see why in 1000 years you would want to go to carb... Hopefully you dont have emissions testing in your area, I doubt you would pass. Its not that hard to keep a fuel injected vehicle running, just keep up on the sensors and maintenance. Unless youre going through 10ft of water it should be fine.. You will lose alot of power and torque.. Anyway, enough of my rant. The only thing I can think of is find a manifold off of a older 2.5l Cherokee with a carb and use that. Is it a manual? If not then you will have problems with the TCU and the trans will pry shift weird, or you will have to disconnect the TCU and manually shift it, you will only have 2nd 3rd 4th and no TC lock..

mike10114

It is a manual.
And the Engine is half way out the door with 250+ miles on it.
I can get my hands on a few fuel injected engines, but no carbed ones.
So I wanted to change a fuel injected to a carb.
But could I swap a 2.5l manifold onto a straight 6? or would I have to find another 2.5l fuel injected.?

mike10114

Nobody knows if this is for sure possible. Because i'm not bothering buying another motor just to have to use fuel injection.

89Laredo

"But could I swap a 2.5l manifold onto a straight 6? or would I have to find another 2.5l fuel injected.?"

I thought you where talking about doing this to a 2.5l? thats what it says in your information...

Anyway, if you where talking about doing this to a 4.0 I THINK they where carbed at one point, so you SHOULD be able to find an old carbed manifold...

Jamie57

Again the question is why?
I used to do tuneups for a living when we used points and condensors. Since we went to computers I'm now doing home renovations for a living.
Why? well it's not because I don't know computers. I build them for a hobby.
It's because they LAST SO $%^(()@)@_I$ LONG! Next to NO maintenaince.
So the MYTH ( yeah thats what it is) that computers break down more often is FALSE.

mike10114

I just don't want anything but me controlling my car. Fuel injection sucks. All the sensors are crap, and the "fact" that they have little to no maintenance is disapproved by this forum here. What is the most common reported fix for 80% + of the problems here. I am a straight mechanical man all the way. And computers are the exact opposite of a machine.

I have a 2.5l but I am able to get a hold a few straight 6's. but they are fuel injected. So I was wondering if this is at all possible.??

89Laredo

x2

Anyway, I wonder if a 4.2l (258 i6) intake would fit.. I think the heads are pretty much the same.

Edit: they will.
From Pirate4x4:
Originally Posted by JonsYJjeep:
As far as a 4.2 intake on a 4.0. I dont think it will work. Because the 4.0 headers wont work on a 4.2 head so I doubt the 4.0 intake will fit. I think they have a few different bolt patterns.
It does fit, and I'm running it. 4.2L block, 4.0HO head, 4.0 (early cherowaggon exhaust mani, and my stock 4.2L carbed intake.

Now, I am only commenting on the head/intake/exhaust compatibility, as far as making it work on your MPI 4.0 engine, no experience here.

Jaffer 06:31 AM 04-18-2006
LOTS of guys have put their 4.2L intake back on after a 4.0L head swap.
There are some port and manifold hold down misalignment issues that need attending to.
If you are an incompetent crybaby who isn't any smarter than a die grinder, then don't try it.

uglyjeepoffroad 06:46 AM 04-18-2006
I am running the same intake (offenhauser dual plane) on my 4.0 head now that I used to run on my 4.2 head. You have to "adjust" the alignment holes a little to make it fit right. Its not hard.

resqme 10:29 AM 04-18-2006
Agree with all, the intake will interchange, the exhaust will not, the distributor will, and you're a meathead for not fixing your EFI.

Metmknice

Put in a 4.2L then, less hassle and should bolt in. They say some XJ's came with 4.2Ls but I have never seen any.

Jamie57

I didn't say No Mainenance. I said NEXT to no maintenance. Big difference.
We aren't talking the HAL 9000 or a Terminator here.
Oh well have fun. Anythings possible if you throw enough money and time at it.
Be sure to bring spare parts with you on the trail. Points and condensors break down too.

4.3L XJ

What the mechanics may have been saying is that it is not legal to do so. Some states if not all have laws about disconnecting pollution control devices.

But on a mechanical note. Just find a 2.5L carburated manifold and put it on with a carb. But after you do that, you will notice a loss of horsepower. The reason is that the fuel injection does not depend on air velocity to keep fuel atomized. The result is an intake manifold that would be the equivalent of a very high performance manifold requiring a very high idle to stay running. But, do what you want.

mike10114

I live in Idaho. None of my vehicles have ever been inspected.... Luckily.

Im not aware of any laws here other than the Cat's one.

But so what you are saying is that being carbed would just require it to breathe much more than it would hooked to all that junk in a fuel injection system.

So a chrome air cleaner that sits right on tope of the carb with no external/Auxiliary junk would feed it enough air... Or did I understand that wrong.

89Laredo

I think you understood it right. Thats why forced induction helps so much in carbed vehicles, it helps keep the fuel moving and atomized...

mike10114

Ok. Thanks guys that did help.
But I'm still sticking with the classic and best Carb.