Well, after putting up with the pathetic LA 3.9 for four years, I decided enough was enough. I found myself a 1993 Dakota LE rust bucket with a healthy 318 and got to work. The plan was simple: put the magnum 5.2 and 46RH from the 2wd 1993 extended cab into my 1989 short cab/box 4wd. However, I found there wasn't a lot of reliable info when it comes to actually doing this swap in an original first gen, so I decided I'd post up some info for anyone else looking to do this.

Between the two trucks, I had almost everything I needed. I wanted to keep the fuel injection on the 318, so I knew I'd be pioneering a little bit with the wiring.

1. Engine - The magnum 318 long block from the donor was a direct bolt-in swap with my LA 3.9 motor mounts. I used the all the magnum accessories (alternator, A/C compressor, power steering, etc.) to keep the serpentine belt set up, which gave me more room. There still isn't much room between the radiator and the water pump pulley, but it fits. Needless to say, I had to remove the stock clutch fan.

2. Transmission - My old 42RH (A500) was having issues, so the 46RH (A518) was the only option for me. The 46RH out of the 93 was a 2wd, so I had to swap overdrive units with my 42RH in order to attach my 4wd transfer case. This wasn't hard to do. It is a direct swap. No disassembling of the internals was necessary. Just un-bolt, slide the OD off, then slip the new one on and you're good to go. I used the same cross-member from the 42RH to mount the 46RH. My 89 trans cooler lines were close, but I had to do some serious bending to get them to fit out of the way. Unfortunately, I broke the 93 dipstick while pulling the engine and trans, so I had to bend my 89's to make it fit without leaking.

3. Fuel system - Since I wanted to keep the fuel injection, I had to swap out the entire fuel system to the 93. This included changing the fuel tank (the 15 and 22 gallon tanks are externally the same size), filter, and pump. My old lines were bad so I ran new high pressure plastic lines from the tank up to the fuel rail.

4. Computer (PCM) and wiring - This was by far the most difficult part of the entire swap. Obviously, I had to use the 93 OBD I computer to keep the fuel injection on the 318. I also used the 93 power distribution center/fuse box in addition to my original relay center/fuse panel to power everything. There is a lot of splicing to be done between the old wiring harness and the new one. Get some wiring diagrams for this part. You will definitely need them!

5. Cooling - Both radiators are essentially the same. I used the 93 radiator because the top port on my 89 radiator came out right at the magnum A/C compressor, making it impossible to attach a hose. If you keep your LA accessories this shouldn't be a problem. For fans, you will have to ditch the clutch fan. There is just no room. I'm still exploring my options between electric and low profile flex fans.

6. Exhaust - The 318 I bought luckily came with some chrome shorty headers. I had to use the 93 y-pipe to fit to them without leaking. Since the 93 pipe was a larger 3" OD, I had to use reducers and flex pipe to mate with my 89's custom system.

7. Misc - I spliced my old cruise control components to the 93 computer and swapped cables on the unit to fit the new throttle body. Throttle cables will need to be swapped. If you want to keep your A/C, you will need to use the hoses that fit whichever compressor you choose to use. Condensers are the same.

The end result: HOLY SMOKES! There is so much more power, it's unbelievable! Admitted, there were times halfway through this swap where I had just about had it, but it's definitely worth the trouble in the end. It sounds a lot better than the v6 through my system too, especially with those headers.

There's a few kinks I'm still working out, but it's almost all finished. I'm sure there are things I'm forgetting, so I'll update this list as needed. Let me know if I forgot something important. Hopefully this info can help anybody else with an original first gen achieve some real Mopar power.

 

Why was there a lot of wire cutting and splicing? Are the wiring harnesses that much different between the TBI trucks and the MPI trucks that a lot of the plugs were different?

 

There is a big difference in wiring harnesses. For example, my 89 had 2 connectors on the computer, the 93 only has 1. Between the 8 new injectors, gauges, sensors, cruise control, and PDC, there were plenty of wires to be spliced.

 

All you would have to do is take out all the wires from the 89 and take all the wires from the 93 and put them in its place. cos one all the wires are gone in the engine bay all you have to do is string the new wires from the 93 and your good too go. the only thing is adapting the throttle cable. I have a 1991 and I took the throttle body motor crap out and replaced it with a 1992 318 fuel injected motor and just used all the computer and wires from the 92

 

Cool. Nice write up. Now where are the PICTURES!

I will put link this post in the FAQ2.

 

Although it wasn't as simple as that for me (I had all sorts of electrical gremlins when trying to use just the one harness, and some connectors were completely different), I probably could have done the wiring better, but since it works as is, I'm not going to complain. Not to mention, there were way more extra wires coming off the 93 harness.

I'll post up some pics after I deal with the extra "spaghetti" coming from the wiring harness lol.

 

all that matters is that you got it too work in your truck. Glad you have it up and running and with alot more power than you did....congrats

 

Mirado, hope you're still around, I got a question or two man!

Your swap was very similar to mine. I'm midway into swapping a '92 Magnum into my 89 Dak 4x4 (was a V6). I'm also going the full Magnum fuel injection route with engine bay harness, fuel pump & tank swap, etc.

Right now my 5.2 is sitting in the 89 V6 mounts, in the truck, and the PS bracket is hitting the steering gear box. How close is your bracket and steering box? I'm thinking I grabbed a pump/bracket from a non-Dakota vehicle, and maybe they're not all the same. If you could check your clearance in that area & tell me what you see I'd sure appreciate it.

edit- I just noticed this post is dated from Sept 2012 not 2013. Didn't mean to create a zombie post...