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How to: KA24DE swap into 720


Crytek89

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I just recently bought a 1984 Nissan/Datsun 720. It's a single cab 5 speed 4x4 with 122k miles. The previous owner out in a 32/36 Weber carb so it runs good but its in need of a rebuild. I stumbled uppon this thread and am intrigued by the work @Crytek89 has done swapping in a KA24DE into his 720. While my truck still runs and drives I am pondering the possibilty of accumulating parts based off your list to eventually do this myself once it is no longer my daily driver. That being said I have a few questions for you and others who have done this swap.

 

Regarding the motor I have found there are two options, FWD and RWD; logic would say get a RWD motor but most of the ones I have found are out of S14 or 240sx and are more expensive. Would a FWD motor work? Visually I can't really tell the difference between the FWD and RWD motors.

Next would pertain to the wiring aspect of the fuel injection system. Did you go with a standalone ecu, or did you reuse the KA24DE ecu? I'm sure ill have to get wiring diagrams of my truck as well as whatever vehicle my donor motor comes out of to figure out my wiring.

Next is mounts. I see that @]2eDeYemakes mounts for the 620 pickup that seems to work for this swap but need minor modification? Other than motor mounts, all existing mounts will work?

And finally Im wondering about the oil pan setup. I know it needs to be modified and cut/rewelded. will my truck being a 4x4 change anything? Will it clear the front differential or will I have to go another route?

 

This is not a project I plan on tackling in the immediate future; but would like to start gathering parts now. Any help/info/advice from all you would be great.     

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The S13 or S14 240sx are RWD (rear wheel drive) engines. A FWD (front wheel drive) engine is mounted transversely (or sideways) in the engine bay. The Stanza/Altima have FWD KA engines.

 

The car KA is also much heavier than the Hardbody truck block. The car intake manifolds are nicer than the truck intakes and the car wiring is on a separate harness that is much easier to separate from the car than the truck harness is from the truck.  

 

 

If using ]2eDeYe's engine mounts and the 720 transmission that all you need. If swapping in the stronger 71C transmission already on the KA then you will need a different transmission mount (I think Steve has those also) and the drive shaft will need to be shortened.

 

240zx engines have a large crank girdle and modifying the oil pan for use in the 720 is more work. Even more work if clearing a front differential. A truck KA is similar to the 720 with a 'front sump' so probably easier to mod.

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So then I guess what I'm wondering is this; if I pull the KA24/71C out of a 4x4 D21 I theoretically wouldn't have to do as much screwing around to get it in the truck(mounts are available to be bought)? But then I'd want to think about getting the intake maifold and wiring harness from a car KA24? And then it'd just be figuring out the wiring for the injectors etc.  

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1 hour ago, 906-Runner said:

So then I guess what I'm wondering is this; if I pull the KA24/71C out of a 4x4 D21 I theoretically wouldn't have to do as much screwing around to get it in the truck(mounts are available to be bought)? But then I'd want to think about getting the intake maifold and wiring harness from a car KA24? And then it'd just be figuring out the wiring for the injectors etc.  

 

 

Yes, this is essentially the way to go.

 

I am still not sure why the mounts were modified, but these trucks are old and sometimes used as trucks and may not be as straight as they once were?

I have had one other person have an issue like that with his 720, not near as drastic.
I made him a custom mount to correct the issue when he contacted me about it. 

The wiring is fairly straightforward if you can read a wiring diagram or 3 and you trucks original wiring hasn't been too hacked on.

Currently helping a guy who got a truck that was swapped and had all the wiring unplugged and all the relays on the floor. 

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I think DatsunMike hit the nail on the head with his answer.

 

]2eDeYe, in doing my frame swap I made a video detailing each area of the swap with the cab off (coming soon). On my original frame the mount seemed to be bolted back further than what it should have been. Not sure if the mount was replaced at some point or not though. I'm finding lots of goodies as I get deeper into this project 😂

 

With the new frame, originally SD25 diesel, i had to drill new bottom mount holes, in which case I could have kept your original mounts as-is and adjust my drilled holes accordingly. 

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21 hours ago, 906-Runner said:

Next would pertain to the wiring aspect of the fuel injection system. Did you go with a standalone ecu, or did you reuse the KA24DE ecu? I'm sure ill have to get wiring diagrams of my truck as well as whatever vehicle my donor motor comes out of to figure out my wiring.

 

While there's lots of standalone ECU options available (megasquirt, nistune, haltech, Enthalpy etc..), I went with the stock ECU, mind you there are many different versions and some will benefit you more than others.

 

Each stock ECU will have a number on it, this indicates whether it's OBDI, OBDII, Federal Emissions, Cali-specific, manual or auto.

I went with a Federal Emissions with Auto ECU, and I only did this because the auto ECU has no speed limiter.

Edited by Crytek89
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