v6 4.3 swap

[jlicea1]

I have a 1985 Nissan 720 love this truck but dont really use it I have a 94 chevy van and am really thinking about swapping drive train and make a fun drag truck. Any one done anything similar to this

[datsun 160J SSS]

It will drop right in  I have a 73 620 with a 97 vortec 4.3 v6  Googel mounts and headers these are still made for the Datsun to chevy swap .

[jlicea1]

This is great news I thought it would be really difficult to drop. Did you have to get shorter drive shafts and if diff could handle extra torque if I upgrade the 4.3 engkn

[dat77sun]

i have a 4.3 in my 82 720 4x4, look at my build for details

[opie931246]

I am also wanting to swap a 4.3 into my 720 4x4. What do I need to do to make this work? 

[datzenmike]

Lots of research. and then some more. The 4.3 will be EFI so a higher pressure fuel pump is needed. Better cooling than the 720's rad will do. Dual or single exhaust??? You'll need a 4.3 transmission. Custom engine mounts, will the oil pan clear? will the starter clear?

[opie931246]

Thanks for info! I figured the fuel system would need to be changed. Going to run single exhaust. The starter and oil pan should clear from what I can tell. From what I've read on other sites I can still use my 5speed trans with this swap. And will look into the engine mounts. I'm assuming I'll have to wire in the computer too and run electric fans/ water pump due to size restrictions. Any other tips would be awesome thanks.

[bottomwatcher]

Your 5 speed probably wouldn't last a week!

[datzenmike]

6 hours ago, datzenmike said:

 You'll need a 4.3 transmission.

 

It's understood (to me anyway) that it will be much easier to mate a GM 5 speed to this engine than trying to find or make an adaptor for the weaker 720 5 speed. The 71B does NOT mate to a GM product.

[Charlie69]

You forgot custom drive shaft.

[opie931246]

Got the new tranny and drive shaft has already been built. Thanks for the info guys. 

[DrvnDrvr]

I've always thought that it would be easier to put a 720 cab and bed on the stronger S-10 frame and drivetrain with the 4.3 Vortec engine than jam the Vortec into a 720.

[Patthedog]

I have a 83 Nissan 720 4x4 to best of my knowledge it’s factory as can be . Bought it off a guy had let it sit in the woods 7 years said the clutch was bad . Long story short the clutch and transmission was garbage and 3800 dollars later I had a rebuilt / new transmission and new clutch. Also had AC retrofitted for an extra 900 bucks . Truck had 160,000 when I bought it has 170,000 now have driven it across state lines and am pretty tired of the 2.4 gutless wonder under the hood . I’m making 23 Mpg with a camper shell on and I loose speed going up hills in 5th so I’m considering a 97 4.3 vortec myself and converting the intake over to the Affordable fuel injection factory TBI application. I’m aware of the fuel system that would need replumbed and needing a new custom drive shaft from a GM 4l60e to my divorced transfer case but I keep seeing there is a kit to put a gm motor in these trucks and can’t find it to save my life . I’m seriously thinking a 4.3 would get close to same MPG double the power and allow me a automatic with overdrive and possibly colder AC as they didn’t change my compressor when they retrofitted this one . 

[datzenmike]

23 is excellent mileage on a camper and the 4.3 automatic won't give that. The 5 speed is only for highway cruise and is intended to be down shifted for passing or climbing hills.... or windy days. In comparison the Z24 will seem gutless but this is what gives you the mileage and it will last forever.

[620slodat]

I have a 1997 (currently parked and uninsured because of lack of funds) and 1998 Astro vans with the 4.3 Vortec (6 of the 8 cylinders in a 5.7 V8) and 4L60E automatics in them. I don't know what rear end gears they have, but I run 225/75/15 tires (both vans drive and act the same). I have towed a single axle 17 ft. travel trailer, and a 21 ft double axle travel trailer over Santiam Pass with the 97. The 4.3 is Vortec is a very strong motor, and has a very long life if taken care of. Currently over 285K miles on the 98, and the motor is still running strong. But, in my experience the 4.3 Vortec will not be a good gas mileage motor. I get in the neighborhood of 15 MPG driven around here locally. I have gotten up to just over 19 on a long run (very heavily loaded down) on I-5.

Edited January 7, 2019 by 620slodat

[Stoffregen Motorsports]

On 1/6/2019 at 5:52 AM, Patthedog said:

 I’m considering a 97 4.3 vortec myself and converting the intake over to the Affordable fuel injection factory TBI application.

 Swapping over to a TBI would be taking a step backward. Do you know what EFI is on the motor now? SCPI or MPFI?

 

 

[Patthedog]

The only reason I was considering the TBI injection as to a carbureted 4.3 or the vortec multiport 4.3 is the carbed 4.3 I have never liked runs rich lacks power . The multiport vortec style I would love to have but to adapt that electrical system over to my already cramped 720 would be a nightmare plus that’s a high pressure fuel system to make that even start and frankly I’m not a fan of the plastic intakes on them . However the TBI injected 4.3 that you would find in say a 87 to 93. Chevy S-10 or Astro van or even the full sized Chevy trucks there is a kit made by affordable fuel injection that plugs into all the GM original components on your 4.3 ECM and all and you only have to add 3 wires to your Nissan wire harness a constant power a 12 v keyed power wire and a ground . This gives you fuel injection a 02 sensor and all the other sensors that allow a motor that will start and run correctly no matter the temp outside and not run rich unless you tell it to . So the TBI intake on a 96 vortec with the higher compression heads would be ideal for my particular swap both in simplicity but cost as well  . As for MPG ( and this is prolly wishful thinking ) I’m hoping the weight loss from what the 4.3 was designed to pull and what my Nissan actually weighs will keep me in the 20 mpg range .  I did a similar swap on a 75 El Camino went from a 2 barrel carbureted 5.7 that got 10 mpg on its best day to a tbi 7.4 that actually pulls 15 mpg no matter what and the best I’m figuring was the 7.4 wasn’t even having to try to pull that car as it was designed for so much more . I’m still in the thought processes in this however trying to gather as much info as I can I love my little truck just don’t like the gutless part lol

. 

[Stoffregen Motorsports]

I have used wiring from Affordable and had problems. They didn't seem to know a whole heck of a lot when I had to trouble shoot the problem I had.

[Patthedog]

I have used them twice got one perfect one and one that just never seemed quite right if that makes sense . I know there is another company that makes a kit to use the original vortec multi port injection on a 95+ 4.3 but it looks like a lotta work and ten thousand ways it could go wrong for me lol . Not 100% sure but I think the 94 and up 4.3 multiport set up was taller too and from what I read in other conversations my truck being a 4x4 I would already need a 2” body lift to pull this swap off anyway so a taller plenum might get me in trouble . Super wanting to do this but so many ways I could ruin a good truck if it goes wrong 

[datzenmike]

Doesn't the 4.3 have some kind of electric carb? Much like the ECC used on the 720? Has a solenoid for a main jet that opens and closes constantly to vary the mixture with an O₂ feedback to a control unit. I had a 4.3 from a FWD Cadillac and it was this way. The carburetor is a Quadrajet. 

[Patthedog]

Never looked too hard into the early carbed 4.3 . I know some of the cars had em like the Chevy caprice the Monte Carlo and El caminos  and full sized base model trucks some was carbed then they went to Throttle Body Injectors that some folks called a carb but was actually two big fuel injectors a IAC and a TPS  and a MAP sensor in the form of fuel injection . Cadillac however I’m not sure because they had actually been fuel injected in some models since 79 however I think sometime in 85 and 86 they did have a quadrajet that had a lot of stuff on em that most folks would rip these off at the first sign of problems and put on a older fully adjustable carb . I have a 86 El camino that has the wiring for this carb but that carb is long gone .  

[datzenmike]

Sorry thought it was a chev 4.3

 

It was 2 years('81-'82 I think when they ran a Buick 4.1 V6.. They were so embarrassed the next year they went back to V8s. A 4.1 liter V8. ?

[Stoffregen Motorsports]

Those were bad days for Cadillac. Almost drove them six feet under.

[85 Nissan 720]

On 9/12/2018 at 8:55 AM, datzenmike said:

Lots of research. and then some more. The 4.3 will be EFI so a higher pressure fuel pump is needed. Better cooling than the 720's rad will do. Dual or single exhaust??? You'll need a 4.3 transmission. Custom engine mounts, will the oil pan clear? will the starter clear?

It does not have to be efi I would go carburetor I am going to do it too my 85 720 one of these years hopefully 🙏

[datzenmike]

Also isn't the 4.3 pig heavy and a gas guzzler?