1982 SD25 Build Thread

[SLO720]

Early this year I acquired a 1982 SD22 truck with a locked up motor. The previous owner bought the truck out of Missouri and had it shipped to him, the truck was originally from California and is almost a rust free truck. Minus the doors and wiper motor area. A few month prior I picked up a SD25 motor and decided that was the perfect candidate for this motor. Picked the truck up for $200 and dragged it home. The SD25 I picked up was a 10 hour round trip from where I live and I helped the guy I bought it from pull it out of the original truck (only 58k miles on the truck/motor). The truck is currently waiting paint and body from a friend of mine. I have new front and rear glass seals, will be painted in tractor enamel paint, floorboards will be bed linered as well as the flat bed in the back. Will also be painting the frame, possibly doing a small body lift to clear larger tires, and a spindle brake upgrade in the front to V6 calibers and a beebani kit in the rear for 4 wheel disc. 

[SLO720]

[wayno]

What injection pump you have on your SD25 engine?

Are replacing a SD22 engine for the SD25 or are you pulling a gas engine out of the truck?

[SLO720]

Replacing a cali emission sd22 with a federal SD25. That SAS swapped truck was originally 2wd and the guy never finished it, I bought the motor and transmission from it. swapped it to the slow glow plugs and swapped out the dpc contoller to match the SD25 motor. Also had to change out the FL engine mount as it made the motor set too far forward. The injection pump is a kiki inline pump 

[SLO720]

I did do a couple of "fixes" on the SD25 after I got it the fuel return rail was hodge-podged together parts of it were brazed and then held together in the middle by clamped rubber hoses. The air filter assembly had a hole drilled in it and a rubber hose run to it from brake booster. The alternator was replaced with a gas one and the vacuum pump deleted. I didn't add a diesel alternator back. I swapped it out for a Maxima alternator and mounted a 6.9/7.3 vacuum pump where an A/C compressor would have originally went. 

[SLO720]

[wayno]

I changed my SD22 engine out to a SD25 and I didn't change a thing, the DPC Module don't care what diesel engine you have as long as it is an inline injection pump.

Glow plugs do matter, you have to have the slow type to use in this wiring harness with the components it came with.

I would use a diesel alternator with the vacuum pump on the back because I put the turbocharger where you have that vacuum pump, I will never again drive a Nissan SD25 engine without a turbocharger

[SLO720]

Maybe my module was bad off the SD22 harness but it would turn to start then rotate back to stop when you tried starting it. I have thought about doing a turbo but I planned to do something crazy and it wouldn't be under the hood. I wanted to do something crazy and mount it in the stack I plan to have coming out the flat bed. I know people do rear mount turbos under cars and they're not exactly practical but it'll be something different. I plan to do a full ST interior with electric windows and interior I have already mounted an egt gauge, and am running a splitter for the dummy light and a mechanical gauge. I like having a higher amp alternator it will help later on with a larger stereo and led lights and all I plan to run. Also have the rest of a Nissan fog light kit to install to go with it. I have a set of blue st electric window doors but I need to find a set in black.  I have a lot to do with this never ending project but I love tinkering with it I guess you could say. Are you running a rotary injection pump or inline with a turbo? I've heard of using a td27 pump but idk about that (was in a really old thread I had read). I also have an LD28 to mess with once I get the chance.

[SLO720]

[wayno]

My engines both have the inline injection pump, I do have a rotary type pump, actually the complete assembly, but I figured out how to turbocharge the inline pump before I got around to changing everything out.

Fact is I figured out how to set it up as a draw thru first before figuring how to do it to a blow thru, but the draw thru had issues that didn't allow anyone else to drive it as they could have blown it up, but the blow thru has no issues, just about anyone can drive it normally, but long uphill passes still need the EGTs to be watched, I don't want it to go over 1400 degrees.

I expect you could mount a turbo in back of the cab but you will have to pipe it back to the engine and have it be air tight, I have a inter-cooler in the 720 and that is like a long pipe, but neither of mine need that inter-cooler, neither of my engines run that hot, I just piped the inter-cooler back into the system because it was already installed in the truck so I used it.

 

Keep in mind that both my diesels are SD25 engines, I helped my friend turbocharge his SD22 and I was not impressed, I expected more.

Edited September 11, 2019 by wayno

[SLO720]

Hello again Wayno, sorry for the late reply, I'm definitely interested in learning about how you turbocharged your engines, turbo size etc. I would definitely prefer a blow through set up for my truck and making a rear mount set up air tight shouldn't be too difficult with quality supplies. I'll be happy to have this thing on the road finally even if its ridiculously slow. After I get this one done I need to do a cab swap on my 86 4x4 and work on my 72 k10 (needs rockers and a lot of other stuff lol). Time just isn't one of those things I seem to have a lot of.

[wayno]

This is how I piped it.

 

The hose/line that goes between the waste gate control fitting and the waste gate vacuum controller can just have a "T" and have that line/hose go to a valve in the cab, open the valve and let it leak a little air and you will have more boost, close it and whatever the stock setting is on the waste gate(usually 7psi) is what you will have for boost, I have mine set for 15lbs of boost, but on the freeway I only have 4 to 6psi going 75mph on level ground.

My 521 SD25 turbodiesel has an OEM 1985/86 Subaru XT turbocharger, it is the best, my 720 has a 1998 VW Passat turbocharger, it's not nearly as good/impressive as the Subie turbocharger, I was so lucky I found that turbocharger, I went from 71hp to way over 100hp, but I don't actually know what it is putting out, but it is a pleasure to drive on the freeway now, it is my favorite vehicle to take on a trip.

Edited September 13, 2019 by wayno

[SLO720]

I apologize for not being on in such a long time! Thank you for the information and this will be helpful when I look further into this matter. My SD25 feels gutless but right now its on oversized rollers as Its basically only run to move around the yard. I really hope I can get back on the project over winter. It still has the stock 3.8 ratio rear in it but has 255s on the back lol. I have a set of st wheels that I'll probably put on it soon just so it'll be more motivated to move. Now that's its cooler I'm also starting to see more blue smoke at start up. I think this motor is due for valve stem seals at the least (30 years old and only 58K miles means it sat a lot).

[wayno]

When I start my engine when it is cold outside it also smokes until it is hitting on all 4 cylinders, they all do when it is cold, but it clears right up after it starts idling smoothly.

I am turning 3.30 gears with P205/70R14s in the rear of my 521 kingcab diesel truck and if Nissan made 3.0 gears for my H190 I would be using them as I have the toque to easily get the truck rolling, I can tow other Nissan 720 diesel trucks with them gears.

I will say that the 1985/86 Subaru XT turbocharger I am using on my 521 kingcab is a way better turbo than the 2001 VW Passat turbocharger I have on my 1980 Datsun 720, it still has a shitload of power but drives totally different, I have not tried an aftermarket turbocharger that ebay sellers say is the same and will work on a 1985/86 Subaru XT because I never drive the 720 so I don't see the point.

I have thought about trying a small diesel turbocharger made for a 2.5L diesel engine as they are out there, it would be interesting to see if the 1.9L Subaru XT gas turbo moves the same amount of air as the 2.5L diesel turbocharger.

I am so happy with my 521 kingcab the way it is right now that I don't want to touch it in fear of not having the same truck after touching it, whenever I do anything to it I save everything so I can put it back to the way it was before messing with it, I recently changed from ABS tubing to 7071 tubing and it didn't change the driving characteristics so I was happy as that was an upgrade, the ABS was deforming because of engine compartment heat, the aluminum should not have that issue.

This is my setup on my 521 kingcab.