New 4.2 or new 4.0?

[olymunch]

So I have a guy that will replace my motor with a brand new engine that comes with a 70/10 warranty and rebuild the tranny/transfer case/clutch for around 2k.

Originally I was just going to instal the mopar mpfi kit but the kit being $1200, I thought I should have the engine gone through when this deal was offered to me.

My question is, should I get a new 258 4.2 and install the mpfi with the 4.0 upgrade or is there a newer 4.0 that already has fuel injection that will install right in instead? I'm really trying to get as much power and reliability as possible out of my sx4.

There's nothing wrong with any of my drivetrain, it sat outside for days in below freezing temps and fired right up. I just figured that if I was going to upgrade it I'd go all the way. I can't wait to have a 30yr old brand new car.

[mudkicker715]

4.0l were always fuel injected. all should be a direct bolt in for the 258. some people have noted that the axle mounts may not be threaded. the holes are there its just a matter of tapping them. thr 4.0l's i have seen and built were threaded.

[olymunch]

Ok, as I understand it, people take a 258 4.2 and convert it to a 4.0 to get better all around performance, but an engine that's already a 4.0 would be the same or better then an upgrade?

[captspillane]

A 4.0 is much better than a 4.2 because of the head design. A stock 4.2 was rated at 115 HP and a stock 4.0 was rated at 190 HP. A 4.0 will always start considerably more readily and will get the same or better gas mileage but put out much more power. The other huge advantage is the increased pressure in the fuel rail makes the fuel atomize much better than a low pressure carb jet, but that's just an advantage to TBI and MPI over a carb. You can put an MPI intake on an otherwise stock 4.2 and you'll have an engine with about 160 HP because of the poor head design.

Even better than a 4.0 is a 4.2 short block with a 4.0 head. This gives you longer stroke, slightly smaller pistons, and a slightly bigger overrall displacement. The difference is barely noticeable, but that does translate to as much power as a stock 4.0 but even more torque. By overboring the 4.2 short block during the rebuild you'll have a 4.5L engine.

A Jeep Stroker typically refers to a 4.0L short block with a 4.2L crank, which creates compression issues unless you shave the piston, but benefits from the larger piston size of the 4.0. Keeping the original 4.0 bore size also gives you 4.5L displacement, and overboring it gives you 4.7L or 4.9L displacement.

I prefer the 4.5L made from a 4.2 short block over the 4.5L stroker because you retain the possibility of using the mechanical fuel pump and a carb. The 4.0 eliminates the hole in the casting for the fuel pump.

[GRONK]

I'm a fan of the 4.2 block w/ 4.0 head myself.  I prefer to keep things simple w/ the 2150 carburetor/manual fuel pump.  Save the $1200+ from the injection and add the 2150, HEI distributor, stainless steel headers and still have close to $550 in change left over for other uses.

[olymunch]

So I guess if you had to choose between upgrading a 4.2 to a mpfi 4.0 or just buying and installing a 4.0, then the smart money would be on just installing a new 4.0?

Would I be right by saying that it is less involved/cheaper, keep in mind I'm no mechanic and will be paying someone to do this, to have a new 4.0 installed?

Is the 4.0 still 258ci?

[captspillane]

No, the 4.0 is 242 cubic inches instead of 258 cubic inches. It has larger pistons but a considerably shorter stroke, causing the 0.2L decrease in displacement.

If you have the choice between a 4.2L and a 4.0L crate engine, the 4.0L long block will be slightly better because it will already come with the better head. The best solution is to order the 4.2L short block, without the head, or rebuild your old short block. Then buy a 4.0 head. Your mechanic won't blink an eye at bolting a head onto a short block to make an ideal long block.

[olymunch]

Ok but don't you also need to change more then just the heads if I went the 4.2 route? And won't a crate motor either come with the fuel injection intake or at least be much cheaper to acquire?

[captspillane]

The other difference is that the camshaft has much larger lobes on the stock 4.0 than the stock 4.2. That's a huge difference I forgot earlier. The much larger lobes on the camshaft are needed to actually get all of the available power from the block. The 4.0 also has longer lifters for a slightly larger oil pump volume. Its a negligible advantage and you can just use your 4.2L lifters and pushrods without worry. The 4.2L has shorter lifters and longer pushrods to equal the 4.0L longer lifters and shorter pushrods. Do not use 4.0 pushrods with 4.2 lifters!

Ideally you should put new rings and bearings in your 4.2L short block, a new "RV" crane cam for low RPM power with the MPI, 4.0 lifters and pushrods, and a 4.0 head from a 1992 Jeep Cherokee (best casting). If you don't want to pay for extra work inside the engine, the 4.0L long block is the best off the shelf option with the proper camshaft and head to get the full potential from the MPI kit.

Its true that the 2150 conversion is much cheaper for simpler and almost as good, which is perfect for most Eagle owners, but some of us will never be pleased with less than the best. There is no equal to the MPI in peformance.

[olymunch]

What is the 2150 referring to?
So it sounds like, and it's what I'm thinking, that a 242 4.0 crate is the best "for the money" option? How would the ecu respond to putting the 242 4.0 with fuel injection in?
My Eagle is a 1981 5-speed and shift on the fly conversion. You have a 6-speed? How fast is that??

[captspillane]

The 2150 is a common motorcraft carb found on 1988 Ford trucks and such. It doesn't restrict the airflow and doesn't have the reliability issues that the original one does. Gronk has a very cost effective kit for sale for converting to the 2150. Most Eagle owners go this route because they do not want to pull their engine or spend much time or money.

The 2006 NSG370 6 speed has different set of shift points, but its not any faster or slower because of the transmission. It benefits from a very low first gear and approximately the same overdrive (I match it to 3.07 gears instead of the perfect 3.54 gears for a T5, and the end product makes 6th feel exactly like the T5 5th). Second gear is very close to first on the T5, so I think of it as a built in middle range. I'm using a NP242 transfer case. I like those much better than the available viscous coupling transfer cases.

Intake manifolds do not come with a long block.

ECU? You will need the entire wiring harness to go with the intake manifold. If you want someone else to install it for you, you're best sticking with the Hesco wiring harness. Its already modified for easy installation, but its considerably more expensive than a used harness. You'll also need their crank sensor on the harmonic dampener kit and their fuel pump.

[GRONK]

Captspillane,  We need to meet sometime and throw down some beers and turn some wrenches......

My suggestion getting back on to original topis is to spens some time poking through the forum.  EVERYTHING you need to know has been posted in great detail many tomes over.  There is more information on this site than in any book you could ever buy.

[olymunch]

Captspillane,  We need to meet sometime and throw down some beers and turn some wrenches......

My suggestion getting back on to original topis is to spens some time poking through the forum.  EVERYTHING you need to know has been posted in great detail many tomes over.  There is more information on this site than in any book you could ever buy.

I absolutely agree with you, this site and eaglepedia are amazing, but I'm a carpenter not a mechanic. I can change parts, diagnose, and trouble shoot but more than half of the lingo and references I just don't understand. I've never done anything as complicated as what I'm going to do and just need very specific questions answered. Again, I'm hiring an actual mechanic to do the work but on one hand I don't want to get 5k deep into a project that I only saved 2.5k for and on the other hand I don't want to get fleeced at the shop. 

[68AMXGOPAC]

OK masterminds ( with all due respect ). My answer to his question , which is a basic question if I am reading it correctly is - he is not taotally mechanically inclined , has to rely on a mechanic , wants reliabilty and simplicity, but some gains in knowledge which he is aquireing by yours and everyones experience and knowledge in comments.
 :)that was long winded but covers my butt,lol.

I would think for him a simple complete 4.0 conversion replacement swap would be the ticket.

I personaly am intriuged by all the options, but on the other hand am allways sitting on the fence as what to do.Point in fact - I have 3 Eagles and a complete 4.0 engine sitting seperate, and still haven't made a choice or tackled the projects. One is Tougeagles Caroiline Conversion car , wich is a great resource , but needs #6 cylinder work.A running 82 SX/4 aka The Money Pit , and an 84 wagon.Let alone my 68 AMX.If I had the cash I would just let someone else tackle it like he is thinking, and just want to drive it.
Yes per say it takes alot of the fun out of the build, and also distances you from  knowing what you actually have under the hood and it's technicality , but for some, a simple solution and a quick turnaround to have a reliable and driveable end result is all they are looking for.As said just my opinion. Good luck no matter what.

[olymunch]

Hey thanks.
Ya that's pretty much it.
 However IF I had the room, I live in an apartment, I might pull it out and weekend warrior that sob and finally know what goes where on the interior of an engine. But I don't, but I do have the foresight to know my own limitations  and still do what it takes to get it done.
I think after all the good info I got today I'll go with the 258 4.2 crate engine and mpfi kit for now. All the outer components are basically new and will be reused and when it's done I'll basically have a new drivetrain. Then later on, hopefully not to later, I'll upgrade the 258 to a 4.0. I think stepping the cost in this way will be the best thing for both my eagle and me;)

The first step is to get it modern/reliable and the second step will be modification.