1987 4x4 3.9L swap - Dakota Durango Forum
Gen I Dakotas 1986-1990 Dakota-Specific Questions

 
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post #1 of 14 Old 01-29-2019, 01:10 PM Thread Starter
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1987 4x4 3.9L swap

I have a 1987 4x4 Dakota with a 3.9L that I am looking to swap to a V8. I have done quite a bit of reasearch the last few years and have find lots of different information. I am looking for the best engine to swap it with. What year, size and everything else I need to know to put a V8 in my truck. Also looking to find out what modifications need to be done. From what I know, almost anything I do is going to require me to change the motor mounts. I would like to know the easiest way this can be done as I am not a fabricator by any means. Thanks for the help.
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post #2 of 14 Old 01-29-2019, 06:24 PM
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If you're not a fabricator, the best way would be to sell the 87, buy a 91+ 4x4 with the V8, and rock the V8.

That's also the easiest.

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post #3 of 14 Old 01-29-2019, 10:24 PM Thread Starter
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The truck has sentimental value and I do not plan on selling it
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post #4 of 14 Old 01-29-2019, 10:41 PM
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OK.

The Magnum 5.2/5.9 blocks will bolt to the motor mounts.

However, they are a bit longer than the engine bay. This is why the 1991+ trucks are bubbled out in the front.

You could swap the 1991+ grill, bumper, hood, core support onto your 1987 (fenders back are the same), but there's other consideration.

The Magnums are EFI; your 1987 is carburated. The cleanest method would be to find a 1996, or barring that, a 1995-1992 donor for a 5.2, and swap transmission, engine, wiring, all electronics in the engine bay from it to your truck.

You will still have SOME fabrication even with that; but it won't be major welding or anything like that.

(If you pull from a same-wheel-base donor, the driveshaft should also swap across; plan on getting one made to help make it easier to find a donor.)

Before you tackle anything like that, though, buy a factory service manual for your year Dakota, and one for one of the Magnum years (I'd grab the 1996 personally).

Why 1996? That was the first year for OBDII; that was the year they swapped from the SBEC to the JTEC; and last but not least, that's the year that it became almost trivial (in the wiring!) to program the ECU to tune the ECU to suit the user. (Trivial in hardware; not so trivial in the wallet, but tunable via plugin adapter beats tunable just barely by replacing parts inside the SBEC ... )

1995 to 1992 were not as easy to tune, due to the burned ROM in the SBECs; but they may be easier to find.

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post #5 of 14 Old 01-30-2019, 12:22 AM
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The 5.2 and 5.9 will fit under your hood. We may not remember that back in the 80s, Chrysler under the leadership of Lee Iacocca teamed up with Carroll Shelby, and Shelby managed to shoehorn the 318 into the 89 Dakota, which sold as the Shelby Dakota that year, and inspired Chrysler to offer the 318 as a factory offering by 91 (The year they stretched out the front end sheet metal, to better fit the V8)

Shelby made the 318 work in the 89 by ditching the engine driven fan and using an electric fan in it's place. The 318 and 360 (5.2 & 5.9) are basically the same engine block so you could use either. With your truck being carbureted , you can keep things very simple and run a carbureted V8 or use an aftermarket EFI system, such as a Megasquirt, Howes, or equivalent.

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post #6 of 14 Old 01-30-2019, 03:56 AM
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One thing that's not always mentioned is that Shelby also used custom motor mounts that shifted the motor back a couple of inches.

I didn't mention that because 87Dakota4x4 said he wasn't a fabricator; and that calls for fabrication.

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post #7 of 14 Old 01-30-2019, 12:34 PM Thread Starter
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I like the idea of putting a carbed engine back in. What would be the ideal year to replace with a carbed 318/360 and would I have to replace the front clip with that. Or do you think an electric fan and wiring would be easier than replace the clip?
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post #8 of 14 Old 01-30-2019, 08:31 PM
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Quote:
Originally Posted by 87Dakota4x4 View Post
I like the idea of putting a carbed engine back in. What would be the ideal year to replace with a carbed 318/360 and would I have to replace the front clip with that. Or do you think an electric fan and wiring would be easier than replace the clip?
Carb a Magnum, and do the 91+ front clip, best of both.

Be aware that you'll have to do some wiring work. Also, you'll need to have a distributor to do the vacuum and centrifugal advance. I'd still use pointless igntion (maybe a MSD box or something similar).

Magnums were introduced in the 5.2L/318cid in the 1992 model year; 5.9/360 were intro'ed for 1993 model year.

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post #9 of 14 Old 01-30-2019, 10:11 PM
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Quote:
Originally Posted by RalphP View Post
One thing that's not always mentioned is that Shelby also used custom motor mounts that shifted the motor back a couple of inches.

I didn't mention that because 87Dakota4x4 said he wasn't a fabricator; and that calls for fabrication.

RwP
I mentioned it because they existed and though rare these days, not totally impossible to find. There were also a few kits, though some were discontinued, and I also heard you can use the factory V6 mounts, and the V8 will be in the right place.

I'm no fabricator either, but if theres a will, theres always a way. In my case, I didn't let my lack of fab skills keep me from installing a Cummins in my Dakota. I simply hired one, and the cost wasn't too terrible.

Ed

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post #10 of 14 Old 01-31-2019, 12:19 PM
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Quote:
Originally Posted by RXT View Post
I mentioned it because they existed and though rare these days, not totally impossible to find. There were also a few kits, though some were discontinued, and I also heard you can use the factory V6 mounts, and the V8 will be in the right place.
I'd hate for a Shelby to be parted out just for the motor mounts.

As to the "factory V6 mounts and the V8 will be in the right place" - no, not on the flat faced 1st gens.

Oh, you can drop a V8 in there; and even with the serp belt, you have something like 1/2" clearance between a stock radiator and the front of the water pump pulley on a serp belt V8. (V-belt V8s end up right at the radiator).

So, no, if someone says "I'm not a fabricator" and also asks for "the cheapest and easiest", that's just flat out. Paying someone to fabricate ratchets the price up (as it should! The person fabricating deserves to be paid for it!)

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post #11 of 14 Old 01-31-2019, 01:08 PM Thread Starter
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I plan on doing the work myself, maybe some help with wiring. I am able to have parts adjusted at my work but not huge overhauls or completely re-doing any major parts. I like the idea of putting the 91 front end on the truck with a 5.9. Any other problems I would have doing this kind of swap. Also if I were to buy a front end would it be better if I bought an entire 1991 or similar year truck with a 5.9 or would I be better off buying them separately?
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post #12 of 14 Old 01-31-2019, 01:09 PM Thread Starter
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Also what was the last year the 5.9 was carberauted?
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post #13 of 14 Old 01-31-2019, 02:50 PM
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Quote:
Originally Posted by 87Dakota4x4 View Post
Also what was the last year the 5.9 was carberauted?
The last year the 5.9 was carburated from the factory was ... before it had the Magnum mounts.

OTOH, you can buy LA-pattern Magnum heads (EngineQuest CH318B comes immediately to mind) so you can use a LA carb intake. There are also some Magnum pattern carb intakes made.

(Pick the intake, then order the proper EQ heads to suit is my recommendation.)

That will also take using an LA distributor to get vacuum and centrifugal advance going properly; carefully running the new wiring (since none of the old engine wiring will work now!); and at this point, your transmission will be at risk due to the increased power. So upgrade the transmission; whoops, that new 4 speed auto won't bolt to your transfer case, so matching transfer case also.

If you're going to go EFI, then do note that the Dakota never came with the 5.9 in the first generation; HOWEVER - the 5.2 ECU will drive a 5.9 fine. If you want to be really picky, the 1996 was OBDII and several vendors (Ryan Hogan of Flyin' Ryan Performance, FRP.COM and Marty Fletcher, UTAWESOME.COM comes to mind. Also HemiFever, but I have no link for that) can sell you a tuner pod that plugs in and adjust the parameters. The 1996 will come with the RE transmission if automatic; this picks up the overdrive over the 87 3 speed auto, and if the donor is the same wheelbase as your 1987, and both are 4x4, you should be able to transplant the drivetrain.

But at that point, you've just about "sold the 87 and buy a V8 4x4" level, with a lot more work.

And more money.

You really should define what you want to do, and why you want the work done.

(If it truly has sentimental value, why not just rebuild the motor? .030 over on bore, and a fresh rebuild, and you may be surprised how well it runs.)

One last thing to CONSIDER - the Magnum 3.9 had about the same horsepower (just a bit less torque) than the LA 5.2 had. Might want to keep it looking the same, go Magnum V6, and rewire to support the EFI. See https://www.allpar.com/mopar/318.html for some history on the LA and Magnum motors.

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post #14 of 14 Old 01-31-2019, 11:47 PM
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Quote:
Originally Posted by RalphP View Post
So, no, if someone says "I'm not a fabricator" and also asks for "the cheapest and easiest", that's just flat out. Paying someone to fabricate ratchets the price up (as it should! The person fabricating deserves to be paid for it!)

RwP
The reality of any project is, sometimes theres a part of it you can't do yourself. In those situations you may have to farm out the work. Of course, if you could do everything, you could do it cheaper, but if you can't do everything, the next best option is to have someone who can do it for you. If you ain't a fabricator, hiring one doesn't have to be expensive. You may find that you could probably use a regular set of motor mounts and just have them welded onto the frame where the engine is to be located. No fab work required, just welding. And the cost might be cheaper than a set of universal motor mounts.

Ed

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