Newest Owner of 1986 720!

[Rudok]

Good evening members, I have just re-entered the family of 720's!

I got my first 720 (1985) back when I entered the Marine Corps in 2004 when I got stationed in Yuma, AZ. I kept it for 3 duty stations driving it across the country on 2 different occasions. I ended up gifting it to one of my family members whom did not take nearly as good care of it as I did and it went the way of the junk yard.

Fast forward to my last year in the military and my wife surprises me with this pristine condition all original 1986 with 106,000 miles on it (still has the stock carb).

I decided to join this forum so I can gain as much knowledge and respect for this machine that I probably didn't have for these trucks back when I had my first one.

I would like to keep it in stock configuration just because this thing is in such good shape.

What I have already done to bring it back up to snuff:

-Drained and flushed coolant with distilled water (pulled plug on back of block each time throughout the process)

-Loosened the head bolts and retorqued to 60 ft/lbs one at a time

-Replaced all 8 plugs with oem

-repaired the heat damaged coolant overflow bottle (had a big crack on the inside of it)

-replaced the radiator cap

-replaced air filter

-Changed oil and filter

-purchased replacement PCV but will replace once I do a carb rebuild due to location

-topped off the r-134a (and the ac even works, it was converted to 134 and the compressor replaced already) I will end up replacing the reciever dryer this winter.

 

What else should I be looking to do to keep this beauty going?

Very excited to be back in the seat!

[datzenmike]

OEM plugs were NGK which is probably what you have but worth mentioning. TWO heat ranges: BPR6ES intake and BPR5ES on exhaust.

 

Today's oils have slowly reduced the anti scuff additive ZDDP from over 1,000 ppm to 500-600 ppm starting in the '90s. Newer engines have valve trains that don't need it but I'm not convinced that an almost 40 year old engine can survive without damaging wear on the levels in today's oils. What I recommend is moving down to the diesel oil section and switching to Shell Rotella T4 in 14w40 or 10w30. T4 has a ZDDP level of 1,200ppm. Not to worry if using the weak sauce, it won't wear out your engine before the next oil change. You can switch then. 

 

For oil filters, ANYTHING but those orange ones. NAPA  Gold or WIX are still considered good but stay away from the orange ones.

 

Replace the transmission oil with GL-4 rated 80-90w. Has to be 'yellow metal safe' or compatible with brass synchromesh rings. If it says GL-4 you're good. About 2 liters. You can use GL-4 to top up the steering box also.

 

Replace the differential oil with 80-90w GL-5 oil. One liter

 

Transmission drain bungs have a magnet on them so wipe clean so next oil change (at 30k mile intervals) you can inspect for wear. It's normal to have a black paste with very fine metal particles.

 

Replace the fuel filter and then every 3-5 years.

 

 

[Rudok]

I didn't realize that about todays oils and will definitely make the change to diesel oil on the next oil change. Anything to keep this beauty on the road.

I do stay away from Fram for sure as I have cut open filters in the past and was not impressed by their lack of quality control.

 

I will put the Differential and transfer case fluids as well as the transmission fluid on the list of must do's.

I did the fuel filter tonight, I sure do love how easy things are to work on with these trucks.

 

I adjusted the valve lash tonight also, intake and exhaust at 30 when it was cold. I found that they were around 25 on most and a few were around 35/36 before I corrected them. The stickers are even still there under the hood that tell you what to adjust them too. This truck even still has the under hood heat shield and the wheel well water/debris deflector material intact.

 

I do need to take the carb off and get my hands on a rebuild kit, as it struggles past just under half throttle (it will only get up to about 48mph and is not happy trying to get any faster). Could be secondary jet is clogged, but who knows until I get in there and take it all apart. I found that Oreille's sells the rebuild kit for about $40 and its actually in stock too.

 

On my last 720, I put a Webber 38 on it (should have gone with the smaller one, but I was young... give me a break). I will be staying with the OEM carb for sure. This carb sure does have a bunch of stuff on it that I don't remember being on the Webber... sort of scary, not going to lie...

 

The truck is the California version and has an O2 sensor on the exhaust manifold, so I'm sure there's all kinds of gadgets and gizmos on the carb that make it good enough for the state just to my west. 

 

Wish me luck

 

[Rudok]

I got the Carb out last night and began to disassemble laying everything out in order and taking pictures along the way. I took leave for today and tomorrow so I could have a long weekend to get this and a few other projects done. So  I am expecting to have the carb put back together and reinstalled by this weekend.

I'll upload some pictures once I figure out how to do that on this forum.

[Rudok]

sooooooo....

The carb went back in after I took a full day disassembling, taking pictures, and reassembling. I will have to say that the stock carb on this is quite intricate compared to what I remember the weber being.....

All said and done, it runs, but like garbage......

I think I need to get my hands on a service manual that would tell me what I need to do instead of using my level of common sense (which apparently is not adequate for this job). 

Any recommendations on where to get my hands on a Factory Service Manual?  

[720_Jeff]

eBay is probably your best bet.  Right now, there are a couple 1986 manuals, a few 1984's.  You're not going to find one new at the dealer at this point.

[bottomwatcher]

It's  been a while but I think I was able to download one from the Nico forum for free.

[Rudok]

On 9/18/2023 at 12:18 PM, 720_Jeff said:

eBay is probably your best bet.  Right now, there are a couple 1986 manuals, a few 1984's.  You're not going to find one new at the dealer at this point.

I took a look on EBAY and I don't think that I am willing to spend those types of prices just yet, but I will keep an eye out for sure.

[Rudok]

On 9/18/2023 at 12:23 PM, bottomwatcher said:

It's  been a while but I think I was able to download one from the Nico forum for free.

I'll check out that forum and see what I can find for sure. Thanks

[Rudok]

I did end up removing all the emissions stuff all over the place and I will have to say that this thing runs much better.

I fabricated my own EGR blockoff plate on the intake with a new gasket and a piece of scrap steel laying around.

I cut the egr tube from the exhaust manifold and folded it over on itself to seal it off, worked like a charm.

Removed all vacuum lines except the one going to the distributor and the Air conditioning idle "thing" on the back of the carb near the firewall that pulls from the brake booster.

 

I am still a little stumped about how exactly the O2 sensor does anything on this carb. Can someone school me on what is controlled on the carb? Or even under what circumstances it is utilized... Or should I just remove it also and what I would need to do in addition to just removing it. I have read somewhere on this forum that some people have installed a wideband O2 sensor to aid in tuning the idle A/F ratio and proper jetting.

[datzenmike]

Well you have to ask yourself what your mechanic will charge for an hour of work on your truck. It's probably close to twice what a used FSM will cost you. In addition he has probably never worked on one, so you pay him the learn something he gets to keep and you learn nothing. You should be able to eventually find one for $20- $50.

 

The ECC or electronically controlled carburetor has a solenoid for the primary barrel. It opens and closes rapidly and the amount of time open is varied by the ECU with input from several sensors but most especially the O₂ sensor. By adjusting the on/off time of the solenoid the air/fuel can be adjusted to keep near optimum 14:1.

[720_Jeff]

An hour of work, whew!  Labor is pretty damn expensive these days.  Around me, not sure if anyone is less than $180/hr.

 

 

Edited October 3, 2023 by 720_Jeff

[720_Jeff]

42 minutes ago, Rudok said:

I took a look on EBAY and I don't think that I am willing to spend those types of prices just yet, but I will keep an eye out for sure.

 

Here's a steal of a deal, $50

https://www.ebay.com/itm/314781999184

 

Hopefully you buy it, before someone else see's it

Edited October 3, 2023 by 720_Jeff

[datzenmike]

I've never had any Datsun I've owned, worked on by a mechanic. 

[Rudok]

1 hour ago, 720_Jeff said:

 

Here's a steal of a deal, $50

https://www.ebay.com/itm/314781999184

 

Hopefully you buy it, before someone else see's it

very well, I suppose that I should just succumb to peer pressure on this one. 

[Rudok]

2 hours ago, datzenmike said:

Well you have to ask yourself what your mechanic will charge for an hour of work on your truck. It's probably close to twice what a used FSM will cost you. In addition he has probably never worked on one, so you pay him the learn something he gets to keep and you learn nothing. You should be able to eventually find one for $20- $50.

 

The ECC or electronically controlled carburetor has a solenoid for the primary barrel. It opens and closes rapidly and the amount of time open is varied by the ECU with input from several sensors but most especially the O₂ sensor. By adjusting the on/off time of the solenoid the air/fuel can be adjusted to keep near optimum 14:1.

Ooh, is that the barrel that sticks out the side of the carb with 6 screws on it? Thats about the size of a large pill bottle? I think I know what your talking about, it does have some wires going to it.

I would like to do some experimenting with the jets on this carb though, I can say that I have noticed the engine temp is slightly higher than normal when I'm doing 65 on the freeway (and that's as fast as she'll go right now anyways). Might be running a tad lean, and I don't want to play those games when it gets hot out here in AZ. I'm thinking that I can get a few jets and start experimenting. 

It does great around town, but it would be nice to sustain 65 mph what a slight headwind is coming my way, or when I'm going up a little bunny hill in the middle of the desert.....

[datzenmike]

7 hours ago, Rudok said:

Ooh, is that the barrel that sticks out the side of the carb with 6 screws on it? Thats about the size of a large pill bottle? I think I know what your talking about, it does have some wires going to it.

... I can say that I have noticed the engine temp is slightly higher than normal when I'm doing 65 on the freeway (and that's as fast as she'll go right now anyways).

 

    

Try spinning the clutch fan with your finger. It should offer firm resistance and stop moving as soon as you take your finger away. If it continues to spin, even for a few inches it's faulty and will excessively slip at highway speeds.

 

 

7 hours ago, Rudok said:

very well, I suppose that I should just succumb to peer pressure on this one. 

 

Keep in the bathroom and read every morning. Info in... garbage out. The FSM will pay for itself the first time you use it to solve/fix a problem. If you can't fix it at least you'll know what's wrong and can knowledgeably tell the mechanic what you want done, not the other way round. 

[1001001SOS]

I couldnt imagine having one of these trucks and NOT having an FSM available. It's a life saver.

 

[Rudok]

very well, it has been purchased. got it for $40 on Ebay.

 

Ill check out the fan clutch next. I suppose my brain just immediately goes to the carb running a little lean. 

I would like too experiment with different jets, any suggestions on where to get a handful of jets to play with?

The ones currently installed are 170 and 94

[datzenmike]

Don't mess with the jets. 94/170 is correct for the Z24. IF, and I say again... IF it's  running lean it's more likely the jet may have some dirt obstructing flow through it.

 

When ever I have a heating problem (too hot or too cold) I replace the thermostat. They do not last forever and it's a waste of time and bother to remove and boil it in a pot of water with a thermometer. Just replace it. Don't get the $2.99 from WallMart, get a name brand.b

 

Some causes of running hot on the highway...

 

Slipping clutch fan.

Soft lower rad hose collapses from pump suction. Squeeze it, rev it up and look.

Hard water scale build up inside radiator. Lower coolant level and look at internal tubes.

Air flow restricted through radiator, bugs or debris blocking fins, shroud missing.

 

 

[Rudok]

12 hours ago, datzenmike said:

Don't mess with the jets. 94/170 is correct for the Z24. IF, and I say again... IF it's  running lean it's more likely the jet may have some dirt obstructing flow through it.

 

When ever I have a heating problem (too hot or too cold) I replace the thermostat. They do not last forever and it's a waste of time and bother to remove and boil it in a pot of water with a thermometer. Just replace it. Don't get the $2.99 from WallMart, get a name brand.b

 

Some causes of running hot on the highway...

 

Slipping clutch fan.

Soft lower rad hose collapses from pump suction. Squeeze it, rev it up and look.

Hard water scale build up inside radiator. Lower coolant level and look at internal tubes.

Air flow restricted through radiator, bugs or debris blocking fins, shroud missing.

 

 

Ok ill just leave them alone then, I only bring that up because I'm not really able to get over 60 - 65 mph....

Probably should look at the carb itself and make sure that there is nothing wrong with the vacuum operated secondary.

 

I did a flush on the rad when i first got it but I will do the thermostat next and just do another flush with the cooling system in the process. 

I would never have thought about the lower radiator hose collapsing, I will check that out along with the fan clutch when I get a chance.

The coolant lever is GTG though, so that's a win.

[datzenmike]

Radiator hose. Just watch and rev the throttle by hand. You can also squeeze it.

[Sephakrid]

On 9/18/2023 at 9:18 AM, 720_Jeff said:

eBay is probably your best bet.  Right now, there are a couple 1986 manuals, a few 1984's.  You're not going to find one new at the dealer at this point.

I just picked up one of the 1984 manuals. It is significantly more detailed than the Haynes manual I was using before. I think it was 45 bucks including shipping.

[720_Jeff]

That is great!  Hard to beat the factory service manual.