4.0 swap vs. chevy tbi conversion

4.0 swap vs. chevy tbi conversion

EODmike

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1983 CJ-7 modified, 1985 CJ-7 Renegade stock
Im new to the site and am wondering what are your opinions on a fuel injection swap for the AMC 258 i6 / 4.2l , 4.0 swap or Chevy 4.3 TBI? Trying to figure out which way I want to go with this and which will be cheaper. Any info would be great.
 
I haven't done anything like this myself, but I once read a jeep build blog by a guy who did the gm 4.3 swap into a yj I beleive. It was a very involved process. Enough to turn me off to it.
 
Do the 4.0 if you look'n for cheap and easy. The mfi is better than tbi anyway.
 
First off, none will be cheap :D.

If your AMC 258 i6 / 4.2l is a solid motor then upgrading it would most likely be the least pain in the back pocket and the simplest of the projects without a doubt.
Even if your motor needed a rebuild I would still lean that way myself but ask 10 guy's and your probably gona get as many dif answers.
Rebuilding your AMC 258 i6 / 4.2l with 4.0 head and intake system would be a better setup than a pure 4.0 swap for torque .
As said the GM swap would be a bigger project and maybe not as good an end product IMO.
I guess it also depends on how it would be used?
 
Thanks for the info guys, looks like I will try to track down all the parts for the 4.0 swap I need when I get home from Afghanistan. It sounds like a good winter project. Thanks again for the input.
 
Go to Jeepstrokers.com and read till your eyes burn out. You will have every answer you need after that.
 
Alright, i have another request for opinions. How hard is it to swap a chevy efi v8 in to a cj and is it worth it? My rig is mildly built with 37's and sees all different kinds of wheeling, basically what ever i can get into. Im not looking to go crazy with my jeep just yet. Should I do the 4.0 swap or a chevy v8?
 
It depends on what you want to start breaking. Lots more power and torque so you will be finding other week points in your driveline. You will need new motor mounts, Transmission adapter, full exhaust, radiator, possible shroud, modified wire harness, possible need for a new Transmission if you have a :dung: one, possible new drive shafts if you replace the tranny, fuel pump and electrics, fuel lines maybe, and alot of little nickel and dimer parts.
 
Alright, i have another request for opinions. How hard is it to swap a chevy efi v8 in to a cj and is it worth it? My rig is mildly built with 37's and sees all different kinds of wheeling, basically what ever i can get into. Im not looking to go crazy with my jeep just yet. Should I do the 4.0 swap or a chevy v8?

This isnt the easiest question to answer for sure. If your rig is "mildly built" with 37s you should elaborate on that. The Chevy is going to be more exspensive for the initial buy in price. Your going to want to go with the chevy Transmission as well cause anything that came behind a AMC 258 i6 / 4.2l ( besides a T-18 ) wont handle it. Thats just the tip of the iceberg when we get into driveshafts,wiring harnesses,motor mounts ,clearance issues,exhaust,fuel pump, adapters... Thats just off the top of my bulbous bald head. :D

The 4.0 swap would be a bit easier but require alot of the same mods. If you have the money and the skills to pull it off Id go a V-8 Chevy for the "mud" and have the rest of the driveline rock solid to boot.

Then we go back to your original post wich asks "wich would be cheaper ?" Either way isnt going to be cheap. Heres a link for the 4.0 Aw4 swap. Good guy that will answer some questions for you as well.

Postal going 4.0/AW4 - Jeep CJ-8 Scrambler Forums
 
I cant use a new HEI distributor if I am going to be doing the 4.0 swap can I?

Are you talking about swapping the head or motor ?

If you are talking about swapping the entire 4.0L motor, you use the stock Distributor, as well the harness, ecm, everything.

If you are just swapping the head on your AMC 258 i6 / 4.2l to a 4.0L then you would use an HEI distributor. Dont have to, but would be wise to get the power your paying for.

Oh, and thank you for your service :notworthy:
 
I am going to do the head swap when I get back from this deployment. Just trying to get all the info I can now so when I get home I can jump right in. Thanks for all the help guys, I really appreciate it.
 
I am going to do the head swap when I get back from this deployment. Just trying to get all the info I can now so when I get home I can jump right in. Thanks for all the help guys, I really appreciate it.

Everything youre going to want to do is very well documented, on this site as well others, but ask away. One word advice, most of the forum search engines wont accept any query less than 4 characters, so you might try using google for your searches.

If you go up to the search box on this site and type in "4.0L head" you get zero returns, do the same thing on google, but add this sites name to the query, and its 8 pages of returns, try this at google "4.0L head jeep-cj.com", all the returns are on this forum, as well you will find other threads on other forums.

good luck, BK.
 
I went with the small block chevy approach in my CJ. The main reason for going that route, was parts availability. I used to wheel my jeep pretty hard in the middle of no where, and breakdowns among the group were inevitable.

It was not uncommon for one of us to put a rock through a oil pan. I challenge any one of you to find me an oil pan for a AMC 258 i6 / 4.2l ,AMC 304 ,360 or Iron duke on the shelf at your local parts store, it just won't happen. Now on the other hand you can walk into just about any parts store, and find a cheap china made "chrome" oil pan for a small block chevy, to at least get ya home from the trail.

Same deal with waterpumps, t-stats, fan clutches, etc.

Also it opens up a huge window of options for trannies as well. I prefer a heavy duty cast iron unit for both strength and durability, in my opinion a manual Transmission will always get you home. I've already limped my Jeep home with a huge hole in the side of my T-4 . You won't do that with an automatic. You can find the tough SM-465 Chevy 4-speed in any junk yard for pocket change, compared to the T-18 .

The motor mount kit for the small block chevy was only a hundred bucks, and is extremely easy to install. The most expensive part with installing the chevy engine was the adapter from Novak to mate the chevy 4 speed to the Dana 300 .

In my opinion it is one of the best swaps you can do in a old CJ. You get gobbs more power, a multitude of engine options, supreme parts availability, multitude of tranny options, you get HEI ignition, run just about any carb of EFI system that fits your budget.

I'll hop off the soapbox now that I added my $.02
 
What small block chevy did you go with for your swap? I would like do go with a small block, was thinking a 5.3L as a jeep is so light that would have good power. I have a 14 bolt rear and Dana 44 front so Im not too worried about breaking axles.
 
I cant use a new HEI distributor if I am going to be doing the 4.0 swap can I?

4.0 head or engine? The 4.0 engine uses a computer controlled advance same as if you go with the MPI fuel system alone.
 
What small block chevy did you go with for your swap? I would like do go with a small block, was thinking a 5.3L as a jeep is so light that would have good power. I have a 14 bolt rear and Dana 44 front so Im not too worried about breaking axles.

I have a freind with a parked CJ5 LTI350 conbo with Dana 44 axles broke front and rear.

Oh and not to sound to negative, it is one BAD sounding CJ.
 
I have a dana 60 siting in my garage, that will find its way under my cj so I am not too worried about axles. Driveshafts will be the week point then, that is if i decide to go with an sbc swap instead of the 4.0 head.
 
What small block chevy did you go with for your swap? I would like do go with a small block, was thinking a 5.3L as a jeep is so light that would have good power. I have a 14 bolt rear and Dana 44 front so Im not too worried about breaking axles.


I used a '88 350, for two reasons, they came with the center bolt heads that in my opinion have much better valve cover sealing, and it's very easy to make it TBI for later when I decide to inject the Jeep. The
Chevy TBI system from 88-95 is dirt simple, super cheap to get, and has plenty of support from the aftermarket if you decide to change things up, like cams and such.

I also have the full floating 14 bolt rear, I don't think you could brake one of them with a lil Jeep lol.
 
I used a '88 350, for two reasons, they came with the center bolt heads that in my opinion have much better valve cover sealing, and it's very easy to make it TBI for later when I decide to inject the Jeep. The
Chevy TBI system from 88-95 is dirt simple, super cheap to get, and has plenty of support from the aftermarket if you decide to change things up, like cams and such.

I also have the full floating 14 bolt rear, I don't think you could brake one of them with a lil Jeep lol.

One part of the 88-95 TBI you forgot to mention, reliability, and I can also add whether its -35 degrees Fahrenheit, or 125 degrees, it will start and run the same. I personally love the platform. Have owned several with an accumulated mileage in excess of 300k miles combined. About the only thing that will take a dump that will leave you stranded on that setup is the fuel pump, just about anything else can fail and you will still drive it home, maybe in limp home mode, but will still be running.
 

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