Got it to pass smog, the work begins now... 1986 Nissan 720 project

[A guy named Rick]

Just confirmed vacuum leak at base of carb. Used Redline adapter and have correct gaskets, and tightened down well. So I'm not sure why it's leaking.

Edited July 20, 2021 by A guy named Rick

[datzenmike]

The adapter bolts are problematic. It's more than common for them to vibrate loose and leak, then owner over tightens the bolts, cracks the adapter.... and it leaks.

 

Use some kind of thread locker on the bolts studs.

[captain720]

Use a product like gasgacinch or permatex aviation grade make a gasket on the gasket. Just a small amount is needed.

[Charlie69]

I use blue loctite on all my Weber studs and bolts.

[bottomwatcher]

Make sure the manifold is completely flat where the adapter plate sits. Mine had some casting flashing that didn't bother the stock carb but the adapter plates didn't sit flush.

[A guy named Rick]

So I took it all back off and looked it over. The adapter is pretty flat, I held it up to the light against a straight edge. What happen was there's a metal piece that sits there on the stock carb, under the plastic heater spacer, it kinda goes down into the intake a little too. Well, I left that off.. I put that back in with the gasket that goes under it, then the adapter and gaskets over that. Solved the leak there. The only vacuum leak I have now is from the opposite side now, closest to the motor, and that one is only slight.

 

I'm going to make new gaskets out of some slightly thicker gasket material. I also need to work on a better throttle return spring set up. Pulling to the side isn't doing the trick, I need to have a spring pulling more upwards. Other than that, it runs pretty decent. I only took it around the corner for now. I'll update later this week.

 

Oh yeah, hey Mike, I never could fully get rid of the off idle stumble with the old carb, but now with the weber there isn't any! That felt so good to not have a stutter from idle. I was even worried the weber would do it because it did before when I had it on there, but not this time.

[A guy named Rick]

This is my return spring rigged up currently. Definitely Roadkill style.

 

[Charlie69]

Here is the return spring on my Weber, 86 720.

 

 

[A guy named Rick]

Quite similar, in angle, I need to get a little more upper pull on it because I'm able to still rotate it the tiniest amount that allows the idle to change. You may not be using the linkage that came with the carb huh? A lot of people swap the old linkage to it.

[A guy named Rick]

Got home from work, went for a quick drive, and uh, it sounds like I lot of air being sucked in the carb when it's just the primary going. But man when you let the secondary open it comes alive. You get that angry intake sound people love when they put a cold air intake on. Maybe now I just need to work on jetting? 

 

Mains 140/140

Air correctors 170/160

Emulsion tubes F50

Idle jets 60/55

Pump jet 50

Float jet 2.00

 

Edited July 22, 2021 by A guy named Rick

[captain720]

Consider buying a generic small block throttle linkage return kit and using that, there's a lot of options and you just need an "arm thingy" to mount to the base of your carb. For my small block I also bought a selection of springs for 10 bucks and tried them till I got something I liked

[A guy named Rick]

Some hand crafted gaskets made from rubber-fiber gasket material. Going to throw those on tomorrow with some blue threadlocker on the studs.

 

 

 

 

Edited July 23, 2021 by A guy named Rick

[Charlie69]

Use the thread locker on the allen bolts also.  Anyting going into the intake manifold to mount the carb gets blue thread locker.

[A guy named Rick]

Probably wouldn't be a bad idea for me to go back through the bolts on the intake manifold and put some on those too huh? I didn't use any when I had did the intake gasket.

 

But yes I will use on the allen bolts too.

 

Hopefully when I get it all back together it will run better. Like I was saying, with only the primary open it runs rather sluggish compared to stock, but not rough, just like it feels a little limp. I'm thinking leaning out from vacuum leak. Also I hear the carb sucking air when driving but not a whole lot happening you know? 

Edited July 23, 2021 by A guy named Rick

[datzenmike]

The intake mounting bolts are fine. They never come loose.

[Charlie69]

The exhaust manifold bolts and studs need loctite.

[A guy named Rick]

2 hours ago, Charlie69 said:

The exhaust manifold bolts and studs need loctite.

 

...gives me something more to re-do. Haha

 

Well, I added loctite, added my gaskets, reset to factory settings and then adjusted. They're not kidding when mentioning it "may run like a tractor". I am now idling fine around 1 and 3/4 turns out from lightly seated, indicating i am lean. Before, with the slight vac leak, I was around 2 I believe. I know it was for sure 2 or more, obviously to compensate for the extra air leaking in. Should I jet up to 65 idle, and maybe 145 main? Or leave at 140, idle to 65, and mess with air correctors/emulsion tubes first? 

 

I just realized too that I capped off the T from the vacuum advance to the EGR, and also the line from EGR to the other round vacuum device above it. Thus, breaking the "do one thing at a time" rule. 

Edited July 24, 2021 by A guy named Rick

[Charlie69]

This should help you,

 

[A guy named Rick]

1 hour ago, Charlie69 said:

This should help you,

 

 

 

I saw that diagram earlier. Should I maybe remove the plug for the EGR and use it? I do have the vapor vent line hooked up.

[Charlie69]

I do not have mine plumbed that way but I would try using the EGR port and see how well it works.

 

I have not had any time to work on my trucks for a few months now.  When I do get freed up there is several things I want to try with my Webers and different set ups.

 

I have a 1986 720 king cab that I have had a new Pierce Manifolds Weber DGEV on since 2011 just after I bought the truck.  I have a 1984 720 King Cab that I have a rebuilt Z20 for and it will get a used Weber DGEV installed when the Z20 is in the 84.  I also have my 1966 520 that I have a rebuilt L20B and a rebuilt automatic trans in that will get a new Carbs Unlimited Weber DGEV when I get the exhaust and wiring done.

 

I have run Weber DGEVs on my Datsun/Nissans since the early 70s.

 

Edited July 24, 2021 by Charlie69

[A guy named Rick]

Wow I completely just realized I'm stupid. Under 2 turns means it's too rich. So I need to jet DOWN, not up. Hmm 🤔

[A guy named Rick]

So I didn't know if I should make an advert for a vehicle that's not mine, I found on Craigslist. But someone is selling an '85 4x4 in SoCal supposedly with the fuel injected 2.4 but I was under the impression those weren't until 1986.

 

Anyways, here's the link. https://ventura.craigslist.org/cto/d/simi-valley-85-nissan-4x4/7352672994.html 

[datzenmike]

 

 

The Throttle body Z24i was available April '85 and on and most '86 model years began May of '85 a few in June. So there will be a few '85s with the Z24i but most are '86 model years.

 

The seller is probably going by the build date saying '85. ALL '86 model year 720s were built in '85. It's weird.

[A guy named Rick]

4 hours ago, datzenmike said:

 

 

The Throttle body Z24i was available April '85 and on and most '86 model years began May of '85 a few in June. So there will be a few '85s with the Z24i but most are '86 model years.

 

The seller is probably going by the build date saying '85. ALL '86 model year 720s were built in '85. It's weird.

 

Yeah like mine, built in June of '85. I always tell the parts guy at the auto parts stores it's an '85. Makes it easier.

[datzenmike]

I bet if you said it was an early '86 model year you'd get Hardbody parts.