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1985 4x4 KC from Sweden


Knugcab

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I heard somewhere that the pistons in the SD engines don't like boost....but I don't know.

The fender flares are from RP Glasfiber in Sweden (in my hometown actually), http://rpglasfiber.com/

I guess I have to trim both the flares and the fenders....but haven't started on that work yet.

The tires are 31".

I don't know if it is lifted, I think it rides higher than pictures of stock 4x4 720s I have seen, and more wheelgap even though the tires are larger, but I have no idea, 720s are getting rarer than hens teeth in Sweden now, and very few of them are 4x4 so I haven't seen one in person in many years to compare with....

 

Since the cab mounts are rusted to pieces and the rubber starting to be worn, I will look into the possibilities of a minor bodylift too later.....

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I have an SD25 engine, and I believe that all SD25 engines came with turbo pistons, at least that is what a guy that did a LOT of research on this subject told me.

So far I have read a lot about turbocharging the SD series engines, I have read a lot of threads about it, I have never read a thread that had a happy ending except mine, all of them have had major issues, or would not build any boost from having to big of a turbocharger in my opinion, I bought the engine I have in my 720 now from a guy that said it ran great, well it didn't run great, it ran way too hot(EGTs), and it really didn't have any power on the hiway(above 50mph), it took me a few years, but I finally figured it out, it runs great and it goes fast for one of these diesel engines.

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I have the inline injection pump that has the vacuum operated throttle, it's a real pain to turbocharge that type injection pump, you have the VE type pump, that one should be easy to turbocharge.

I have not driven this a lot, but the guy that had this before me daily drove it, but as I said, it ran too hot, but he drove it like a grandpa, I seriously doubt he had it over 55mph unless it was going down hill, but I cannot drive 55mph, so I had to redo it all so I could drive it, I have run it up to 3000rpms in 5th gear with 3.30 gears in the rear with stock type 14 inch tires, I don't know how fast I was going because the speedo is way off, I suspect I was somewhere between 90 and a 100mph, my EGTs were not an issue, and I was up around 15psi boost.

I heard somewhere that the pistons in the SD engines don't like boost....but I don't know.

The fender flares are from RP Glasfiber in Sweden (in my hometown actually), http://rpglasfiber.com/

I guess I have to trim both the flares and the fenders....but haven't started on that work yet.

The tires are 31".

I don't know if it is lifted, I think it rides higher than pictures of stock 4x4 720s I have seen, and more wheelgap even though the tires are larger, but I have no idea, 720s are getting rarer than hens teeth in Sweden now, and very few of them are 4x4 so I haven't seen one in person in many years to compare with....

 

Since the cab mounts are rusted to pieces and the rubber starting to be worn, I will look into the possibilities of a minor bodylift too later.....

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It's kinda hard to explain if you don't know how the inline injection pumps work on the diesel trucks we got over here in the USA, but I will try to explain.

The inline injection pump we have are run by a vacuum throttle, there is no throttle cable going to the injection pump, there are vacuum lines that go to the injection pump from the carb looking thing that I call a throttle body, this throttle body has a venturi in it that is connected to one of the vacuum lines, the other one is a vent that goes to the intake tube that goes to the air filter, so the line connected to the venturi creates vacuum when the butterfly in the throttle body is closed(when you let off the pedal), this vacuum pulls the injection pump rack to the idle position as the spring inside the injection pump wants to be in the floored position, the vacuum pulls it to the idle position when the engine is running, now when you push on the pedal the venturi loses vacuum and the rack moves to a richer position, at the same time the engine is getting more air and more fuel also, so it revs up/makes power, if you floor the pedal the venturi loses all vacuum and the rack floors itself, and when you let off the pedal it creates vacuum fast and the rack gets pulled back to the idle position, this is how are inline injection pumps work, it works fine unless a vacuum line cracks, then not so good.
 
OK, so the guy I bought the engine from left everything in the stock configuration and put the turbocharger in front of the throttle body, now this creates the problem of the venturi being pressurized all the time if the turbocharger is spun up, it creates a lot of pressure between the turbocharger and the throttle body when you let off the pedal, now he put a blow off valve in between the turbocharger and the throttle body, it did let off enough pressure for the venturi to create enough vacuum to pull the rack back to idle along with all the air being cut off it would settle down to an idle, but the moment I would press on the pedal the pressure in between the turbocharger and throttle body would build and the rack would move to the floored position or very close to it, and the only reason it would not rev up is because it could not get enough air, so the fuel would still burn completely as it didn't blow black smoke out the tail pipe, but it did run really hot.
Now the guy tried using a small hose clamp on the vacuum line between the throttle body and the injection rack diaphragm so control this over rich issue, but it didn't work, the engine ran weird, it surged all the time when trying to go 30/40mph, and when I tried driving on the freeway the EGTs(exhaust gas temperature) would rise to 1400 degrees or more, 1400 degrees is melt down time, it's not if it will melt down, but when will it melt down, so I parked it for a while(year), and then I tried using a inline injection pump for a boat or water pump, but I could not get that one to run right either, so I gave up and put the original injection pump back on it and I moved the throttle body in front of the turbocharger, that created new issues that I worked thru till I finally figured it out.
Since you have a VE type pump I am not going to describe how I did it, as that would likely take even longer to explain and you don't have the inline injection pump so you don't need to know, it runs around 800/900 degrees on the hiway doing 70+mph, yours would likely run about the same, the inner-cooler only made a 100 degrees difference, so if I do make another turbodiesel engine for my other truck, I likely will not use an inner-cooler. 
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AH, so the problems came after turbocharging it, I see.

I was just wondering since the EGT seems to be high (though I haven't checked it, but the tip of the exhaust is getting very hot after just a short while, especially for a diesel), I have some starting troubles, and the top speed is, as you said, around 50 mph, though I guess that may be what you could expect from a truck like this?

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AH, so the problems came after turbocharging it, I see.

I was just wondering since the EGT seems to be high (though I haven't checked it, but the tip of the exhaust is getting very hot after just a short while, especially for a diesel), I have some starting troubles, and the top speed is, as you said, around 50 mph, though I guess that may be what you could expect from a truck like this?

 

Yes the EGT heat issues were caused by the turbo, it got way too hot way too fast, but you need to keep in mind that I have another Datsun diesel truck, one day I decided to put a EGT gauge in it also to see what kind of heat a normal non-turbocharged SD25 diesel engine puts out, to my surprise they get very hot also when one floors them.

This is how it worked for me, when I first got the turbocharged engine and installed it in my 720 dually, while trying to enter the hiway the EGTs would get up to 1400+ degrees before I even got up to 55mph, most the time I had to let off before I even got up to freeway speed, since I changed it I will see up to 1200 degrees entering the freeway and it will hover around 800/900 degrees at freeways speeds on level ground at 70/80mph, it will still climb to 1400 degrees on a hill if I push it to keep my speed at 70/80mph.

Now when I drive my Datsun 521 kingcab SD25 diesel I also see high EGT temps, around town it stays under 1000 degrees, most the time it's at 600 degrees, but on the freeway it hovers around 700 degrees on level ground, keep in mind that I drive fast(70/80mph), the faster I go the hotter it gets, anyway between Portland OR and Vancouver WA there is a bridge, it's about a mile uphill grade, not overly steep but up hill, riding a bike up that grade was exhausting, by the time I get to the top I am beat, most of my friends that I ride with cannot do it, they stop and rest, anyway when driving my non-turbocharged Datsun 521 kingcab diesel up that grade, my EGTs climb slowly up towards 1400 degrees, it only gets to 1400 degrees if I floor it trying to keep up 70/80mph, if I let off and go up it at 55/60mph I don't even get close to 1400 degrees, it only gets hot when I start flooring it, but the way I drive it runs very warm on roads that have lots of hills, to go 70/80mph I have to have the pedal 3/4s of the way down all the time, it runs around 1200 degrees all the time, and when I get to a hill 1400 degrees happens fast.

OK, so your truck is a 1985 Nissan 720 4X4 SD25 diesel, it is a very heavy truck, the SD25 is rated at 71hp, your likely not ever going to be moving very fast on the freeway, and when you come to a hill your likely going to have to drop a gear, if your holding the fuel pedal down near the floor to keep up freeway speed, your going to run hot EGT temps, I do, and your temps are going to be hotter as you are pushing a lot more weight.

I first built my diesel 521 kingcab as a 4X4, but I decided that the SD25 diesel engine could not keep up freeway speeds, so I took it off the 4X4 chassis and put it on a 2wd chassis, I have never regretted doing that, as it barely can take how I drive it now, I would have killed it as a 4X4.

Here is how it sits now.

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This is what it looked like when it was first built.

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Here is the 720 turbodiesel towing the Datsun 521 4X4 diesel before it was a turbodiesel.

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You are going to be fighting high EGT temps all the time when driving on the freeway, I would suggest installing a EGT gauge, at least you will have an idea where you are and then decide how hard you want to push it, I will say this though, before I had a EGT gauge I drove my 521 kingcab diesel from Vancouver WA to Los Angeles CA, there is a hill just before LA that one has to get up, I had the truck floored for half an hour, it got hot, my water temp gauge showed real hot, by the time I got to the top of that hill the engine smelt weird/hot, and it didn't have near the power it had when I started up that hill, the truck would barely do 50mph on level ground when I got to the top, it cooled down going down the other side of that hill and drove normally after it cooled, but I would say I was very lucky that I didn't blow the engine up that night a 1000 miles away from home, I have no idea how hot the EGTs got as I had no EGT gauge at that time, but I bet it was close to smoking the engine, I was so lucky that night.

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  • 3 months later...
  • 3 weeks later...
  • 1 month later...

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Sanding the tailgate...

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Welded the holes for the tailgate handle, it was broken anyway...

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Removed the rear pan, it was so ugly anyway after the chain came loose when I tried to pull out a forklift that was stuck... :D

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Primer....

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...and paint!

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Started working on the flares.... Lots of work left but at least one of them is in place now.
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Parking here was hard to resist.... :D

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  • 2 months later...

First, I apologize for all the dead pictures after Photobucket gone nuts.

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A friend was sending his Escort to the junkyard so I took the seats out of it, I think that they can be mounted lower than the Mazda 626 seats that is in it now. The Mazda seats are mounted as low as possible but that's not enough. :(

Also, they are the same colour as the rest of the interior which of course is a good thing, the Mazda seats are blue.

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Chrome door handles is not right on this army green paint, so I gave them some black paint. Will probably dry more flat than this.
I actually tried "Plasti-dip" (actually some cheap knockoff) this time, I really don't like the hype about it, but since you can never get paint to stick to chrome it feels better if I can take the whole thing off and do it again when it starts to peel....

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Yes....it is too hard to remove mechanically, tried to sandblast some rusty, flaking chrome wheels once but I gave up and left them to professionals for sandblasting, though when I got them back most of the chrome was still in place, and as they said they could not guarantee that paint would stick......but with my small equipment one wheel would have taken the whole day, I think.....

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It's getting dark outside so the mocha colored headlights have to go.
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Cheapest halogen alternatives I could find. "World tech made in Taiwan" does not sound very great but getting four Hellas or something like that was a bit over the budget..... Sure, the lights are cheap but I still needed 4 of them. :(
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I will try Osram Nightbreakers since they have a quite good reputation, though I am still not completely convinced that they deserve it. If something sounds too good to be true, it probably is.
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Well, at least I guess that the light output will improve a bit...
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And even though the truck itself is ugly, it improved the looks a bit too, strange enough.

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