My motor has 320,000km on it. Sometimes it doesn't start. Not sure why, I suspect the crappy emission control vacuum lines etc.It's filthy, and runs rough. There also appears to be some weird yellowish/white gunk in the anti-freeze. Probably not good.

How compatible is a magnum vs LA in an early 1st gen dakota? If I keep the old intake manifold, will the computer match up? The fire order is the same right?
Also, will the computer work fine without all the emission garbage?

Reason I ask is I can get a clean fresh rebuilt magnum long block for cheap. I know the later first gens used magnum blocks. First time swapping a different type of motor in a post 80s vehicle. Searched the web quickly, I know people talk about the v8s being almost identical, but no mention on the v6s.
How do you tell if it's an original motor? Can you use magnum engine components in an LA block?

I supposed I haven't mentioned what kind of truck I have.

It's a 1988 Dodge dakota
- 3.9 V6 LA
- NP2500/a535 5 spd manual transmission
- np231 transfer case 4x4
- Long bed single cab


Thanks!

 

a) The intakes don't swap; bolt patterns are different.

b) If you go Magnum, I'd just find a donor truck and swap the wiring etc. also to get better fuel economy and more power.

c) In addition, there's no exhaust crossover in the Magnum heads, so the EGR won't work and the cold engine warmup won't work properly.

RwP

 

That's fine. Exhaust system was shot since I bought it off some kid who did some weird glass pack configuration.

I suppose since the magnum engine uses a fuel injection system, that would require modification to the fuel system correct? Or would it swap directly?

I was also considering rebuilding the bottom end for the sake of numbers matching. Then going to the scrap yard and procuring the rest. Only difference between the blocks themselves is just the valve train. Ahhh making a mountain out of a mole hill. I think I'll just get magnum long block. Less work.
​

 

Uhh ...

No, there's more difference than "just the valve train".

Yes, a lot of parts swap.

HOWEVER.

Magnum blocks, save for a few of the first few year, won't have the oiling path for the LA valve train. Oops. So you get a minute or so run time if that with LA heads on a Magnum. Unless you redress that.

Yes, I'd get a donor truck and upgrade to the MPFI/SEFI from the TBI the LA had. It's what I thought about doing then decided that due to lack of cash, I was going to just get my LA rebuilt.

(If you meant to put the Magnum heads on the LA block, again, the oiling path is different between the LA and Magnum designs; it can be done, but it's a bit of a fiddly pain.)

I didn't mean the EXHAUST manifold was different; those will swap. I mean, as I said, the INTAKE manifold was different. It won't bolt straight up.

There's a jig you can make to drill the LA pattern into the Magnum heads; but I'd have to say, "Why???" A lot of the difference in power output came from three things - 1) Improved breathing of the head design. 2) Improved breathing in the intake, to match 3) Full electronic fuel injection.

RwP

 

A donor truck would be a dream come true. It's damn near impossible to find a donor truck. Nobody locally selling anything. I am probably going to have to source all the things individually. I will need the following: Tried Car-Part, got replies from scrap yards from across the country about shipping control arms, but they never follow through.

-Intake manifold with injectors
-v6 Magnum EFI ECM (from a first gen dakota, unless a 2nd gen will work?)
-Wiring harness with injector wiring
-Obviously the fuel pump on my tank is only good for carb setup as EFI uses higher pressure, so im going to have to get a fuel pump along with the plumbing (if needed)
-Accessories will bolt to the same block, so I can re-use them. Even though I would prefer a serpentine setup. Second gen dakotas have a serpentine setup, but accessories shouldn't be too different?

I won't be doing any of this for another couple of months. Hopefully something shows up and the scrappers before then.

Could be a fun project

 

If you are going to go to all the trouble of an engine swap, why not drop in a V-8??

 

ive considered that aswell. But the early 1st gens weren't designed for V8s. I believe the engine bay front end had to be redesigned to accommodate them at around 1990. Mine is a 1988. I am not sure what was different, maybe rad support? Or maybe it used a serpentine setup. Used to have a 94 Dakota 318, wish I never got rid of it.

At least with the v6 swap I can get EFI, with everything bolting in the same place, minus the headache of getting the engine and accessories to fit having to modify a bunch of other stuff only because of the compartment design. I like the style of early 1st gen dakotas vs later front end dakotas. But if I do come across an EFI v8 at the scrapper in the same period, I may consider. There is an 89 Dakota LE with a 3.9, but LA block. Has bucket seats I might grab though.

Another reason why I am doing this is that I have to do some minor frame work that requires me to remove the engine anyways to get access. I figured I would look at engine while I was there. Anyways, I yanked the engine today, and drained the oil. I saw coolant pour out of the oil plug, so safe to say the engine might have issues I don't know about aside from a leaking gasket.

Thanks again!

 

Yeah, coolant coming out the oil drain is just never a good sign.....

Is this something you need done quickly? Or do you have something else to drive?? Have you considered just rebuilding the 3.9 you have??