My 1980 Datsun 720 diesel dually

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Re: My 1980 Datsun 720 diesel dually

#101

Post by wayno » Thu Apr 21, 2016 6:08 pm

Laecaon wrote:So the whole problem with boost is going lean. New diesels make crazy psi. I would check what vw and Mercedes were doing at the time with their indirect injection motors. I wouldn't hesitate at more boost if you have the fuel to keep up. I would focus more on egt than boost at cruising speeds.

I just got back from adjusting it to where it just gets over 12psi, it was hard to find that area, either it wanted to go all the way to 15psi, or it wanted to stop at 6psi.
I believe you are right about driving the EGTs rather than the boost, but I would rather keep it below 15psi if I can for a while, it still has plenty of power below that.
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Re: My 1980 Datsun 720 diesel dually

#102

Post by wayno » Thu Apr 21, 2016 6:32 pm

I am kinda playing with the fuel mixture now with a boost controller, I figured out how to give it more fuel using the boost to help it, and when I let off the pedal the boost goes away, and so does the fuel, no boost, no fuel.
I still have the vacuum issue though, and I just shortened the spring to much and it didn't help, it just don't idle as good, so I stretched the spring a little and now it idles good again, you see if I have a high idle, I have less vacuum when I let off the pedal, if I have a low idle, I have more vacuum when I let off the pedal, when I talk about letting off the pedal I mean that I am cruising down the road in second gear at about 2000rpms and let off the pedal completely I get 5psi of vacuum, if I almost let off the pedal all the way I only have 2psi, it's hard/strange to not let off all the way, but I am learning how to drive it, I don't know what it does in fifth on the hiway right now as I just got it tuned in today, and I have not had it on the hiway today, I will find out tomorrow when I go down town to pay my property taxes and get tags for 2 of the trucks.
Vacuum pulls oil thru the seal of the turbo, the more vacuum the more oil gets pulled thru, I know this because the inside of the intake is coated with oil.
The vacuum valve was coming apart again, the holes were elongated again, so I drilled 4 more holes in the tube and put 4 screws into the PVC, it is just to hot in the engine compartment for PVC, I am going to have to come up with something made out of just metal.
Here is what I did today after work, I put in an oil filter sandwich adapter kit so that I could mount the oil gauge sensor/sender without worrying that it would break off again, this is what I bought on ebay.
http://www.ebay.com/itm/Racing-Sport-JD ... Sl&vxp=mtr
Here it is mounted, it doesn't seem to be leaking, even though it didn't not seal properly the first time I tightened it down, so I started over and got it right the second time.
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It got kinda oily below the filter when I removed it to put the adapter plate in.
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I am hoping this sensor part is done now, it had good oil pressure, it almost pegged the 90psi gauge when cold while idling, but after warmed up it was about 50psi at 750rpms, I can turn it down to about 500rpms if I want, but it makes the truck shake. :lol:
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Re: My 1980 Datsun 720 diesel dually

#103

Post by wayno » Fri Apr 22, 2016 3:26 pm

I have really high oil pressure on this engine, or maybe it is where I have the sensor mounted, but when I started it up this morning, at a 632rpm idle.
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My oil pressure gauge was pegged!!!
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I have never seen an oil pressure gauge pegged before on any engine at any RPM, but maybe it has something to do with where the sensor is mounted, I didn't show this type of pressure before when it was mounted in the oil galley in the block on that extension that broke off, now it basically shows how much pressure is in the oil filter.
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Re: My 1980 Datsun 720 diesel dually

#104

Post by DRIVEN » Fri Apr 22, 2016 4:42 pm

Is there only one oil galley tap in the block? The one where you had it when it broke off?
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Re: My 1980 Datsun 720 diesel dually

#105

Post by wayno » Fri Apr 22, 2016 6:43 pm

DRIVEN wrote:Is there only one oil galley tap in the block? The one where you had it when it broke off?

There are a few of them, but they are all being used, the one where the extension was is for the dash light sensor and there is not enough room to mount the sensor there, the one at the front of the block on that side goes into the injection pump with weird fittings, the one on the other side of the block goes to the Vacuum pump on the back of the alternator to run the booster for the power brakes, normally I would tee that one and use it for the oil sensor gauge, but it already has a tee and that one goes to the turbocharger, I do not want to put another tee over there, so I ended up buying the sandwich adapter, as I don't trust extensions anymore(I am lucky I still have an engine), and it likely will cost a small fortune to have a braided hose made to mount the sensor remotely where the dash light sensor is, and this adapter with the correct fitting cost less than $10.00 to my door, so I went the cheap route, I cannot even find the first one I bought with the wrong fitting anymore. :(
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Re: My 1980 Datsun 720 diesel dually

#106

Post by wayno » Sun May 29, 2016 8:31 pm

I piped the inter-cooler back into the system today, I have not been using it since I changed the whole system, but when I had to drive up an extended grade, the EGTs got a little high, so I decided to see if it would reduce the EGT temps using it.
When I took it on a test drive, something let loose, so I pulled over and looked things over, and could not find the issue, so I tightened everything up(inner-cooler piping), and everything seemed fine again, maybe when I let off the pedal the vacuum created sucked it back together and when I tightened everything up it fixed the issue.
It drove exactly the same, so I was happy about that.
When I took everything apart to pipe the inner-cooler back into the system I found more oil in the tubes, this worries me a little, you see now the inner-cooler is the lowest thing in the system, so now I am worrying that it will fill up with oil, so unless I drill a hole in the inner-cooler, eventually I will have an issue.
My plan is to see if it makes a difference in the EGTs, if it doesn't, I will remove the inner-cooler completely and repair the sheet metal so it looks stock again.
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Re: My 1980 Datsun 720 diesel dually

#107

Post by Laecaon » Sun May 29, 2016 11:46 pm

wat, a turbo with no intercooler....

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Re: My 1980 Datsun 720 diesel dually

#108

Post by wayno » Wed Nov 23, 2016 11:04 pm

I came across this on the Portland Craigslist a while back, a NOS SD25 diesel head core, the guy wanted $300.00 for a new core which I think is a deal being I have seen them for over a $1000.00 in other places.
So I messaged him and asked about it, he told me that he forgot that the head was in Astoria, and asked me if I wanted him to contact me when he came back to Portland next time, I said yes.
He contacted me yesterday and said he was in town with the head and asked if I was still interested, I said yes, we met today at the Vancouver Mall parking lot next to Macys, I called when I got there and his wife answered, she said they were in a silver suburban and at that very moment I was actually looking at the truck the moment she said it, I drove right to them.
As I parked I looked down and seen a used head as I passed by, I got out and introduced myself to Dustin, I looked down and said I thought this was for a new head core and he said yes, he grabbed that head and removed it from the top of a box that was held shut by metal straps, he said that he wanted me to have this head also for the valves, springs, and the rest of the hardware, and he took it over to my work truck flatbed and put it in the back of the truck, then he walked back to the box on the ground and stared at it, he had no clue on how to get it open, but I had some tin snips in the truck and cut the straps, we opened it and the first thing that was apparent was that it had got wet at some point, it looked rusty to me, but it had waxed paper all over it with what also looked like wax on everything.
I bought it for $240.00 because it didn't look like it had any real rust damage, and I thought I could have a couple thousands cut off of it if I had to, this evening I took a razor blade to it and it actually doesn't look to bad, I think some steel wool will clean it up the rest of the way, so I got one head with cracks between two of the valves on two cylinders complete, and a NOS core head that looks like maybe there is no rust damage for $240.00 which is a deal as far as I am concerned.
This guy talked fast and a lot, I could hardly get a word in at all, he talked for an hour out in that cold wind and I was soaking wet from finishing the roof I pressure washed, I asked him twice if he was cold and didn't even get a reaction from him the first time I asked, the guy said he was an aerospace engineer, he bought 5 heads because he needed one and they wanted him to buy 10 of them, and he talked them into 5, they came from Australia.
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Re: My 1980 Datsun 720 diesel dually

#109

Post by DRIVEN » Thu Nov 24, 2016 7:01 am

Unusual score. What is the large pocket/hole in the deck of the rusty head that the new one doesn't have?
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Re: My 1980 Datsun 720 diesel dually

#110

Post by wayno » Thu Nov 24, 2016 9:58 am

Ok, if you look at the photo you can see the little square hole.
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If you look really close you can see the round piece installed in the photo below.
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Now if you look at the new head you can see the little square hole in the head, this piece above is already installed in the big hole.
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This large hole is the injector pre-chamber, not sure exactly how it all works, but the injector and glow plug are in this chamber, how the fuel gets out of this chamber and into the cylinder is unknown to me as it is just a pocket that is not connected to the intake runner.
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This is the first time I ever seen one of these heads apart like the used rusty one is, this SD25 head has shown me things I didn't know about, I had an SD22 head rebuilt and didn't know about all this removable stuff.
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Re: My 1980 Datsun 720 diesel dually

#111

Post by DRIVEN » Thu Nov 24, 2016 10:19 am

Interesting
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Re: My 1980 Datsun 720 diesel dually

#112

Post by wayno » Thu Nov 24, 2016 12:00 pm

Here is what the injector seat looks like in position, the injector head centers itself in that hole.
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And here is what it looks like with the glow plug in position, I don't understand how the fuel gets into the cylinder, the glow plug is in the way of where that little square hole is if the injector shoots the fuel straight out the square hole.
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I guess I always assumed the diesel fuel/vapor was more or less shot directly into the cylinder via the intake valve/runner like gas fuel injection, but this is a strange way of doing it, I never really gave it much thought before as it ran so I didn't care.
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Re: My 1980 Datsun 720 diesel dually

#113

Post by Laecaon » Thu Nov 24, 2016 1:18 pm

Reason its called indirect injection. VW used this method until the mid 90s. Mercedes did until about 2000. That is your pre combustion chamber.

All new Diesels (in cars) are Direct Injection (directly into the combustion chamber)


http://www.dieselhub.com/tech/idi-vs-di.html

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Re: My 1980 Datsun 720 diesel dually

#114

Post by wayno » Thu Nov 24, 2016 5:58 pm

It works, so I drive it, better mileage than anything else I have except the Mini, but it will not really haul anything.
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Re: My 1980 Datsun 720 diesel dually

#115

Post by wayno » Tue Jan 31, 2017 5:36 pm

I swapped out the shift lever today, I have been using an early one that that more or less is straight up to the shift knob from where the shift lever mounts in the transmission, I put one in from a late Nissan 720(85/86 reg cab/short box), since they have short shafts, the shift lever is tilted back farther, I should have done this a long time ago.
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When I am driving down the freeway at 60+mph in 5th gear, my shift lever would vibrate and make this annoying rattling sound, and I would have to lean forward to rest my hand on the shift knob to stop it from making the noise, this newer lever has rubber(not in photo above) that isolates it from the transmission, I am hoping this rattling stops, if it doesn't my hand can easily reach the lever without having to lean forward now.
Now I have to get used to the new lever, it is way closer and seems lower, it's right next to my thigh in 2nd gear now, feels weird/funny, but I will get used to it.
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Re: My 1980 Datsun 720 diesel dually

#116

Post by wayno » Wed Feb 01, 2017 6:19 pm

I drove it today on the freeway, no more loud shift lever rattling, that was so annoying.
When it is in 1st gear now it feels like 2nd gear, I keep trying to push it forward at signals, eventually I will get used to it. :lol:
It was very windy today at my place, not so bad at the PNP yard in the Orchards area of Vancouver WA, I sure am happy that the neighbor cut them huge decorative Pine trees down, and am happy that they let me have the wood, so now I am warm and not afraid that the trees are going to fall on my house, we have been getting a lot of seriously strong east winds the last few years.
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Re: My 1980 Datsun 720 diesel dually

#117

Post by wayno » Fri Feb 24, 2017 2:01 pm

So I re-did the hood scoop today, I cut off that stupid square one and put another stupid one in it, it is just different.
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I could not get a good photo of the components sticking out of the hood thru the hole.
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It looks better than it did though, but that is my opinion, but one day I need to get around to lowering the turbo so I can put the good stock hood back on, this shit sticking out of the hood sucks.
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I still have to paint it, but it is lightly raining outside, so another day.
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Re: My 1980 Datsun 720 diesel dually

#118

Post by wayno » Sun May 07, 2017 5:49 pm

Ok, so as many of you know I figured out how to turbocharge my 521 that has an inline pump and it runs great as a blow thru, this truck I tried and tried and I could not get it to run properly the way that Larry had it set up as a blow thru, I tried a different type of pump at one point, in the end I made it into a draw thru and fought it till I got it to run decently, but I never felt it was good for a long trip with the vacuum pulling oil thru the seal issue, but I did finally get the power I was looking for.
Well yesterday I looked at this truck and thought I didn't need the lower turbo manifold to see if I could get this truck figured out, so this morning after breakfast I went to work on this one, and it actually didn't take that long.
It is now a blow thru, I didn't need to even use a valve anywhere on it this time as it has an adjustable waste gate, so I put the throttle body back in the stock position, piped everything like the 521 and started it, adjusted the idle a couple times till I had it below 900rpms and I took it for a test drive.
The EGTs run a little warmer than the 521(couple hundred) and I did seen slightly over a 1000 degrees, but otherwise it ran as expected, actually better than expected, Larry had the pump turned up so it is getting more fuel all the way around, I said this before, this engine has grunt/torque, it puts me firmly in the seat when accelerating, it's a good thing I put all the tools I was using in the truck before I left as I needed them, I seen 20psi boost more than once on the hiway when I put my foot in it, the second time it blew the intake piping apart at one of the connections, so I pulled over and put it all back together, I then adjusted the waste gate to 15psi and continued on.
This truck has way more power at lower RPMs and it will kick the 521s ass everywhere except maybe at fast hiway speeds, when I try to drive 75/80mph in this 720 I keep maxing out the boost at 15psi and I really don't like it, at the same speed the 521 is at 5/6psi boost and it will go faster which I am comfortable with, but 15psi plus boost just cruising down the freeway on level ground bugs me, it likely has something to do with the intake vane being larger.
Now I like having the 15psi boost when getting on the freeway, but it's not there all the time when accelerating, I let off and shift gears and such.
In the end/big picture, it was a complete success, it acted like the 521 and didn't have super hot EGTs, I am happy with the results, it did exactly what I was hoping for, it drove normally like the 521 and doesn't have vacuum issues anymore, so this is a repeatable setup and it doesn't need control valves to adjust to get it to run properly except for the waste gate which would have to be tinkered with on any turbo conversion.
My 720 is so much heavier than the 521, yet this 720 will leave my 521 behind off the line, but on the freeway is yet to be determined, turning that pump up does make a difference, although I don't know exactly how it was done other than a diesel injection shop did the modification.
I could hardly believe I seen 20psi boost, I thought I had it adjusted lower than that, as a matter of fact I am sure I had it adjusted lower than that, everything I do to this engine lately makes it run better and better.
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Re: My 1980 Datsun 720 diesel dually

#119

Post by wayno » Thu Dec 07, 2017 8:07 pm

I decided to do a major conversion to the 521 work truck, so I needed another truck to use as the work truck while I do the conversion to the 521.
I decided to make the 720 dually into a temporary work truck, I pulled the dually box off the truck.
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I then put the flatbed with the Tommy Gate onto this truck and got the rear lights working today, I will take more photos during daylight hours.
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It took a few days to do what I have done so far, not working on it full time as I still have work cleaning out gutters and such, once the weather goes bad people will quit calling and I will then start the work truck conversion, I still need to wire a trailer plug so I can tow the trailer, I likely will not wire the electric brakes unless it is scary to stop.
I still have to change out the wheels as the dually rims on this truck are held on by adapters and I do not trust the adapters to haul weight, but I already have what I need and I have the tires to mount on them, will do that in the next few days also.
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Re: My 1980 Datsun 720 diesel dually

#120

Post by DRIVEN » Thu Dec 07, 2017 9:29 pm

I like it.
When the only tool you have is a hammer every problem starts to look like a hippy.

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