4.0 EFI swap into 79 J-10

[jraynolds]

Getting ready to swap a 4.0 with EFI into my 79 J-10. The truck currently has a 258 that is wore out (very low compression and rod knock) with a T-18/D20. I'm looking at only swapping out the engine and hooking up the EFI. I have been trolling Craig's and have found quite a few donor vehicles in my price range ($800 or less) but I am not sure which one to pull the trigger on. Here's a couple questions I have.
- What is the best year range to use for a donor?
- Does it matter if the donor is auto or standard? If so, why?
Right now those are my main questions. I have already put a 5.0 EFI conversion in my wife's Mustang so I am familiar with some of the hurdles in converting a carb vehicle to EFI. Maybe you guys can let me know some of the hurdles specific to this project. Thanks in advance!!

[j2sax]

Look for "5 wires to fire" info for getting the EFI going.

IF you are wanting to keep your standard trans, a standard trans vehicle will give you the proper flywheel. Also, the ECM would have the correct idle speed and there is a difference in one of the TB inputs... cannot recall off top of my bald head.

If it were me and this was not a mainly offroading machine, I would stick the whole 4.0 with AX15 in there and that would solve your placement of a CPS issue as well as give a you a great shifting, rugged overdrive. (without the granny gear of course!)

I like the 91-95 as it has the more easily diagnosed and pre-OBDII engine management system. Prior to that is the Renix system, which is not terrible, but not as easily serviced.

Post 95, you have to integrate much more electronics due to the OBDII system, but that is not to say it cannot be done.

I have also seen several people take the 4.0 and just stick a Chevy Throttle Body on it or get a Howell system. The latter is a more pricey options, but make for much simpler install, the "Junkyard TBI" is cheaper but requires more legwork.

[j2sax]

Look for "5 wires to fire" info for getting the EFI going.

IF you are wanting to keep your standard trans, a standard trans vehicle will give you the proper flywheel. Also, the ECM would have the correct idle speed and there is a difference in one of the TB inputs... cannot recall off top of my bald head.

If it were me and this was not a mainly offroading machine, I would stick the whole 4.0 with AX15 in there and that would solve your placement of a CPS issue as well as give a you a great shifting, rugged overdrive. (without the granny gear of course!)

I like the 91-95 as it has the more easily diagnosed and pre-OBDII engine management system. Prior to that is the Renix system, which is not terrible, but not as easily serviced.

Post 95, you have to integrate much more electronics due to the OBDII system, but that is not to say it cannot be done (though I have not done it!).

I have also seen several people take the 4.0 and just stick a Chevy Throttle Body on it or get a Howell system for simplicity's sake. The latter is a more pricey options, but make for much simpler install and is designed for an AMC 6, the "Junkyard TBI" is cheaper but requires more legwork and tuning.

[Carnuck]

I would do '91-95 EFI with XJ 5 speed and either D20 adapter$ or a Dodge NP208 with 1" spacer/clocking ring from Parts Mike. Or you can do the front crank mounted CPS and run the current trans.

The 6 cyl mounts are the same. '91 up for the motor. Newer than '99 have a few issues but the EFI from '91-'95 will still work.

Renix head is different (intake ports mostly, but it's the same as '90 YJ 4.2L head without the EFI "notches" in the ports) but the carb intake can be "massaged" to fit.

I was going to put EFI in my Eagle (I have everything from a '91 XJ that was 5 speed) but, unless there is a miracle cure for vertigo and old age, not going to happen in this lifetime. Black Jack has the HO 4.0L from a '93 Grand Cherokee (along with the one year only ZJ AW4) and it'll be running LPG (I have the "carb" and modded intake along with regulators, lines and tanks from a converted XJ)

I have an HO 4.0L from another '93 Grand Cherokee I'm parting (it's only taken me a year to get it half parted) with AW4/NV242 that's going to go to the Eagle.

And per usual I was distracted and forgot where I was going?

The automatic HO computer needs trans inputs or it will grossly overfuel/starve, act weird. The std one doesn't need it.

[tgreese]

Another option wrt the 4.0L CPS is to machine a hole in your current bell and mount the factory CPS on your bell. Novak will machine the bell for you, if you like. https://www.novak-adapt.com/knowledge/amc_i6.htm

[Carnuck]

You need the matching flywheel with HO EFI notche$ and clutch too if you go that way. The flywheel on the AX-15 is about 1/2 the weight and uses a different starter unless your 6 cyl is '88 or newer. (XJ style instead of Ford style starter)

[jraynolds]

Thanks for the info so far. I do like the idea of a 5sp, but funds are limited and not sure I have the budget to have new drive shafts made in addition to everything else it's going to take for the swap. Now I have a good starting point on what to look for.

[tgreese]

You need the matching flywheel with HO EFI notche$ and clutch too if you go that way. The flywheel on the AX-15 is about 1/2 the weight and uses a different starter unless your 6 cyl is '88 or newer. (XJ style instead of Ford style starter)

So what's involved in making the equivalent CPS setup for the front of the enigne (rather than buying the HESCO parts)? Is it a notched wheel and a VR sensor? Or some other type of sensor?

[Carnuck]

They use a balancer with holes drilled and I forget what the sensor is. I know Renix uses a different one (micro voltage AC)

[brielly]

One thing that hasn't been mentioned yet is that the 4.0 intake will not fit in your engine compartment with the stock brake booster. You will need to switch to hydrobost brakes in order to fit.

I would also suggest 91-95 as the simplest install. If you are stuck on the wiring hesco sells just the harness which makes the install really easy. I did the full mopar kit years ago and you literally had to hook up one wire to switched power, one to the battery and one to ground. The rest of the wires go to the sensors, fuel pump, etc.

Since you have a manual tranny you need the ecm to match. If you can find a complete truck with ax15 I'd swap the whole drivetrain. Just keep in mind the 94 or 95 and later models had the external slave cylinder which is what you want for ease of replacement.

[Carnuck]

I'm hoping to have a '99+ in take soon so I can test the fitment theory of them and stock booster.

[j2sax]

When you say you did the "whole mopar kit" you are talking about the Hesco, not a 4.0 MPFI setup, right? If not, I would be interested to read the details!

[tgreese]

There is a genuine Mopar kit - http://www.jegs.com/p/Mopar-Performa...08371/10002/-1

I had thought that HESCO is just reselling it.

[j2sax]

Hesco Kit

There is a genuine Mopar kit - http://www.jegs.com/p/Mopar-Performa...08371/10002/-1

I had thought that HESCO is just reselling it.

How do you like it and what kind of mileage do you get? Is it on a 4.0 or 4.2? Sorry for the hijack, though it does seem related!

[brielly]

I have the full Mopar kit on a 4.2 same thing hesco sells. Its been great so far, very reliable and added quite a few ponies using the seat of the pants dyno. Gas mileage is around 15 in town 17-18 hwy with 5 speed tranny. Honestly the mpg's were about the same with the carter carb.