CJ7 add on Fuel injection system

[AuProspector]

I installed the MPFI on my 1978 CJ& back in 2001. It took me 3 days but had to run fuel lines on my vehicle. It is the best mod that I've done so far. I've got over 140,000 miles on it so far. I only had the 1 bbl Carter so there was a big difference in performance after the mod. I also installed a Borla header since I needed and exhaust system with an O2 sensor. I'm now looking at the 4.0 head swap since just last week the No. 6 cylinder's valves start leaking giving me a miss and less power at low rpm.
I can't speak of the throttle body FI since I've had no experience with it.
Good luck on your project.

 

[j0114]

Ive got a Jeep CJ Rebuilders manual 72-86, It goes into detail where they installed a multi port mopar fuel injection on a AMC 258 i6 / 4.2l engine.
For some of the other posts it seemed I had to go with a 4.0 head to use the multi port injection,

Have I misunderstood some where,
would someone give me a link to the junkyard multi port swap,

I really don't want to swap my engine head as It is so new but If the 4.0 is the better route I could sell my AMC 258 i6 / 4.2l

thx for everyone being understanding with all my questions.

Iv e touched on this before but my jeep mechanic skills aren't the best but Im not a newb,
I have done many other jobs with imports several years ago with hondas engine - Transmission - axle swaps
So I Have had experience with engine work and i have put engine swaps in Suzuki samurais including 1.6 16 valve fuel injection from a 1.3 carb model.
So i think i can handle the job especially with the books and manuals I got

 

[Sasquach]

The 4.0 head goes hand and hand with the MPI system in my opinion, sure you could install the MPI on the AMC 258 i6 / 4.2l head but you would not be realizing the full potential. A 4.0 and AMC 258 i6 / 4.2l head side by side on the workbench tells it all, Better intake port design-bigger intake ports-smaller combustion chamber-intake port shape at manifold to accomodate injector.
I too had just had my AMC 258 i6 / 4.2l head machined prior to the Mopar/4.0 head upgrade but now think it was the right decision to go foreward and never look back.
This system transforms your AMC 258 i6 / 4.2l motor as advertised and I was surprised at the outcome on mine. Things more often than not are overated but this does not fall into that catagory. Only downside(Mopar) in my veiw is the cost but you do have the junkyard option, see thisguyyouknow's junkyard MPI system.

 

[Rescue Diver]

I'm pretty sure the multiport FI intake from a 4.0 will not even physically fit on a AMC 258 i6 / 4.2l head. The 4.0 head has the intake ports raised much higher than the AMC 258 i6 / 4.2l head, so I doubt the intake and exhaust manifolds would clear each other if you tried putting them together on a AMC 258 i6 / 4.2l (AMC 258 i6 / 4.2l ) head. The 4.0 head also has some notches machined into the top corners of the intake ports to make room for the injectors while the AMC 258 i6 / 4.2l head doesn't have them.

Maybe it'll still fit but I seriously doubt it. I would verify before buying the parts.

Either way, the 4.0 head is so much better than the AMC 258 i6 / 4.2l head, that not doing this swap while you're doing everything else just doesn't make sense. You'll gain a lot more performance and fuel economy from the 4.0 head swap than you will from the fuel injection anyway.

I had only 5,000 miles on a freshly rebuilt AMC 258 i6 / 4.2l head when I did the swap, so you wouldn't be the first to have wasted money getting the dinosaur head rebuilt and then replacing it with a 4.0 head.

I recovered some of my losses by selling my old AMC 258 i6 / 4.2l head on craigslist after the swap.

 

[Sasquach]

The Mopar system does fit both heads, I think the diff between the two heads in terms of the intake bolt pattern is the locating pins and the Mopar manifold has drillings for either location.
That said, do I recomend the AMC 258 i6 / 4.2l head? Read my above post

 

[Rescue Diver]

The Mopar system does fit both heads, I think the diff between the two heads in terms of the intake bolt pattern is the locating pins and the Mopar manifold has drillings for either location.
That said, do I recomend the AMC 258 i6 / 4.2l head? Read my above post

Does the stock 4.0 system also have both drillings for the locating pins, or just the retrofit kit?

Also, what exhaust manifold would he need to use on the AMC 258 i6 / 4.2l head if he were to keep it? The AMC 258 i6 / 4.2l has square exhaust ports, and the 4.0 exhaust manifold that's made to work with the 4.0 intake is made to fit round ports.

That begs the question of whether the 4.0 MPFI intake manifold would even clear a stock AMC 258 i6 / 4.2l exhaust manifold with them so close together on a AMC 258 i6 / 4.2l head with the lower intake ports.

I'd really be interested to hear from someone that has added MPFI to a AMC 258 i6 / 4.2l head.

 

[Rescue Diver]

Whether the parts will all work together or not on a AMC 258 i6 / 4.2l head, you'll be much happier with the outcome if you do the 4.0 head swap. You'll go from a 110 hp engine that gets crappy mileage to a 200 hp motor that gets much better gas mileage. It's a no brainer for the cost of an easy to find 4.0 head.

Plus, you could do what I did and sell your old AMC 258 i6 / 4.2l parts to get back some of the money. There's always a buyer out there if you're patient.

 

[j0114]

For the condition of my jeep I took advantage of the economy in my opinion, When I bought it no one was buying toy or extra vehicles so I got it alot cheaper than it would have been before or now,
so it will not hurt as bad since I didnt put the new motor in,

A few questions,
I currently am running the AMC 258 i6 / 4.2l with weber carb, and borla headers and full borla exhaust,

If I go with the 4.0 head I know the mopar MPI kit will take the carb out but will I have to replace my exhaust system as well,
the above post made me think that.

--I did some research and the mopar kit does fit the AMC 258 i6 / 4.2l for sure. But As stated above is seams smart if I am going to do the MPI kit it would be good to get the full performance etc from the mod.
To those who did the 4.0 head swap, did you go the junkyard route or did you go with a summit or 4wd.com etc. And I would only need the head correct? I would keep the bottom end of my engine I got currently correct?

--I do want more HP out of the Jeep, Im running 33-12.50's and plan to run
33's and my Jeep pulls them fine but It seems I am on the exhaust alot and I had noticed just dropping a few RPMs greatly increased my gas mileage.
I am not selling the Jeep so I do not care to put money into it, I spent a real long time looking before I bought this one and there were a few things like the EFI I would have wanted it to have but its condition and price , I knew I could always add on and I dont think I would ever find a Jeep exactly like I wanted it unless I built it, I am sure most of you agree.


--will someone give me a link to the junkyard 4.0 swap?


-- Whats the going rate on a good used 4.0 head and what should I expect to get for my AMC 258 i6 / 4.2l head if I go this route?

 

[Rescue Diver]

I bought my 1995 4.0 cherokee head from pick-n-pull for $55 with the aluminum valve cover. I paid the local machine shop $140 to do a valve job and seals. I'm running the stock AMC 258 i6 / 4.2l push rods, the head bolts that came with the 4.0, and I did the bio degradable packing peanuts and JB Weld trick to block the extra water jackets. If your bottom end is a 1980-1986, you'll need to get some head bolt spacers to make your 7/16" bolts hold the 4.0 head centered because they use 1/2" bolts, and you'll need to use the AMC 258 i6 / 4.2l torque specs.

If I remember right, I sold my AMC 258 i6 / 4.2l head for $80.

 

[Sasquach]

Does the stock 4.0 system also have both drillings for the locating pins, or just the retrofit kit?

Also, what exhaust manifold would he need to use on the AMC 258 i6 / 4.2l head if he were to keep it? The AMC 258 i6 / 4.2l has square exhaust ports, and the 4.0 exhaust manifold that's made to work with the 4.0 intake is made to fit round ports.

That begs the question of whether the 4.0 MPFI intake manifold would even clear a stock AMC 258 i6 / 4.2l exhaust manifold with them so close together on a AMC 258 i6 / 4.2l head with the lower intake ports.

I'd really be interested to hear from someone that has added MPFI to a AMC 258 i6 / 4.2l head.

The Mopar system is designed as a CARB legal retrofit for the AMC 258 i6 / 4.2l
As for the stock 4.0 intake you would have to most likely modify for the locating pins and even then it may not work, the Mopar intake can be purchased seperately if you had to do the junkyard mod and were keeping your AMC 258 i6 / 4.2l head although the manifold probably cost what a 4.0 head would cost. If a guy is gona junkyard it why not get everything from the donor?

 

[Sasquach]

For the condition of my jeep I took advantage of the economy in my opinion, When I bought it no one was buying toy or extra vehicles so I got it alot cheaper than it would have been before or now,
so it will not hurt as bad since I didnt put the new motor in,

A few questions,
I currently am running the AMC 258 i6 / 4.2l with weber carb, and borla headers and full borla exhaust,

If I go with the 4.0 head I know the mopar MPI kit will take the carb out but will I have to replace my exhaust system as well,
the above post made me think that.

--I did some research and the mopar kit does fit the AMC 258 i6 / 4.2l for sure. But As stated above is seams smart if I am going to do the MPI kit it would be good to get the full performance etc from the mod.
To those who did the 4.0 head swap, did you go the junkyard route or did you go with a summit or 4wd.com etc. And I would only need the head correct? I would keep the bottom end of my engine I got currently correct?

--I do want more HP out of the Jeep, Im running 33-12.50's and plan to run
33's and my Jeep pulls them fine but It seems I am on the exhaust alot and I had noticed just dropping a few RPMs greatly increased my gas mileage.
I am not selling the Jeep so I do not care to put money into it, I spent a real long time looking before I bought this one and there were a few things like the EFI I would have wanted it to have but its condition and price , I knew I could always add on and I dont think I would ever find a Jeep exactly like I wanted it unless I built it, I am sure most of you agree.


--will someone give me a link to the junkyard 4.0 swap?


-- Whats the going rate on a good used 4.0 head and what should I expect to get for my AMC 258 i6 / 4.2l head if I go this route?

I bought my head from clearwater and it came as a "AMC 258 i6 / 4.2l retrofit" with the jackets welded, machine work done and new valves for $400.
you will need a 4.0 valve cover and that's another good reason to swap as the 4.0 has a better gasket set up and so far zero leaks out of mine, you will most likely need to replace your head bolts and or use spacers depending if you have 7/16 or 1/2" head bolts. Mine had the 1/2" bolts but length ended up wrong and this may vary from the different head casting avail. 7120, 0331 etc.
You will need to also get a 4.0 header, mine was from a cherokee and from there you could have a custom front/down pipe made to go back to your existing exhaust system.

 

[81loredo]

This discussion turned quickly to the HESCO kit. Has anyone been happy with the HOWELL kit?

 

[CJ7WAYNE]

I just installed the Howell kits and it went in smooth and fired up the first time. Runs great. I'd recommend it.