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1985 nissan 720 rwd california daily.


Toxicrain

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Within reason a too large carb will work well enough on a smaller engine. A smaller carb will always work well.

 

The 32/36 is rated at 300 CFM the 38/38 at 360 CFM (although RedLine did say 400 CFM)

 

The L20B at redline (7,000) uses and needs 241 CFM

The Z24 at redline (6,250) uses and needs 263 CFM So right off the bat the Webers are both larger than needed.

 

Why are the CFMs so close? because the L20B can safely rev higher. But in the real world, a stock L20B will run not much over 5,500 before power drops off. A Z24 is about 4,500 (on a good day) so neither are going to reach their potential maximum needs, least of all the Z24. This is not to say the Z24 won't rev to redline, only that you would have to put a brick on the gas and sit down and wait.

 

This is much closer to what you will experience in the real world....

 

L20B @ 5,500 = 190 CFM

Z24 @ 4,500 = 190 CFM

 

Again, the demand for CFM is far far below what even the 32/36 carb can supply. (300 CFM)

 

So lets say you modify the Z24 heavily and it pulls all the way to 6,250 RPMs. You still need only 263 CFM and a 32/36 will do. Yes a 38/38 will work on a Z24 but you don't need it. It's a V6 or small V8 carb and why a popular swap into 4.3 liter Jeeps.

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My issue was getting a 32/36 to idle on only the idle circuit. With the speed screw in 2 turns (to deal with altitude, and a realistic amount of vacuum after 200,000 miles) idle rpms would vary significantly. Higher rpms would increase vacuum and draw fuel from the main circuit after the throttle was resting on it's stop screw, but, other driving conditions would have the opposite effect.

 

The drilled hole allowed me to set the speed screw back to 1.5 turns and get the a/f guage to the sweet spot with out so much closing of the mix screw.

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You only need to rejet for altitude.  A kit Weber is basically set for a factory motor, slightly above sea level.  When you get to 7,000' there is significantly less air in the same amount of space that it consumes.

 

Although you can go with a smaller primary idle jet, or simply turn in the mix screw, you can't turn the speed screw in beyond specification to get the, basically, same amount of fuel that the motor needs to idle on.  Drilling a 1mm hole corrects this.  Larger air correctors and definitely smaller main jets allow less fuel per amount of opened throttle for the rest of the throttle range. 

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  • 4 weeks later...

So im looking at the beltech spindle drop kit with 3" drop blocks and the notes say spindles wont work with 14" rims? Will they work if i have 2" spacers on it and will it fix my full lock rubbing issue against the cab or make it worse?

Running 205 70 14 right now looking to go to 195 55 or similar in the future

 

 

Also wondering if my parts truck with the z22 motor, will the fs5w71B transmission bolt up to my z24 that currently has the L3N71B trans right now? is there any extra things i should get? if it is compatible I might consider the swap in the future or at least save the trans for something else.

 

the parts truck is a KC with 4x4 and my 85 is single cab RWD im not sure if that will make a difference?

 

 

Success! Finally located a used alternator and volts are steady 14.00 at idle and 2k rpms. Now to get a new muffler because the stock one rusted out.

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  • 1 month later...

just an update been about a month now and the truck is running great! daily driven it 50-70 miles a day in various weather and have driven it in 90+ degree weather and I dint have my fuel cut, boil, vapor lock or any bogging issue that I had before the carter pump and holley fpr install. gauge always stays at a steady 3psi. Just want to thank you guys for the help in this thread and now I can save up money again instead of it all going to gas.. ($300 a month in gas better than $500 when driving the dads tundra  :sick: ) damn prices keep going up too $3.79/g from 3.07 back in January...

 

Looking into things I have been adjusting my throttle cable trying to find the best cable springiness and what not..

I have noticed that on deceleration now I get backfire. now my exhaust is setup with nothing past the eBay cat that the PO put in. Stock headers. I took the muffler / tail pipe off because it was rusted out.

I have tried to set the throttle cable forward more to reduce the back fire but if i set it too far forward then when i put the truck into drive the idle shoots up and ill be going 15mph without touching the throttle and when coming off the highway or to a stop I wont have any engine deceleration which then I gotta use brakes more..have to brake harder to stop etc..

 

Anyways. Just wondering if that backfire will destroy my engine or not overtime. I only let it happen when i'm almost at a stop and its only when my foot is completely off the pedal. when im coming off a highway or something ill left foot brake and keep my throttle inched before full deceleration to stop it from popping  ..

 

I dont think its back firing into the intake as I have had that issue before and It is definitely a different sound. Hopefully its not shooting flames under the bed when its popping because I do run my truck slightly rich to compensate for driving at 80 so I dont get any bogging when trying to floor it at those rpm's 

 

Eventually ill go to a muffler shop and get something installed but the truck isnt obnoxiously loud and cops havnt pulled me over for it yet so ill let it be for now and work on my 89' camaro.

 

me being a teenager I kinda do like the pop sound :D and hopefully when the exhaust is completed it will be louder cuz im just trying to have fun with this truck now since I can only drive it until Aug 2019 (rip smog with weber carb)

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Enjoy the pops!!! As long as you have some amount of pipe on there there is basically no danger of bad stuff. I like the exhaust I have on my 2wd (you can hear it on you tube if you want). Mine pops only sometimes or when I want it too, it's the perfect balance. If your not doing emissions just run a long tube glasspack and some pipe, then it won't rust and is cheap. Would recommend at least a welded muffler/glasspack I don't like press together but each his own.

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Enjoy the pops!!! As long as you have some amount of pipe on there there is basically no danger of bad stuff. I like the exhaust I have on my 2wd (you can hear it on you tube if you want). Mine pops only sometimes or when I want it too, it's the perfect balance. If your not doing emissions just run a long tube glasspack and some pipe, then it won't rust and is cheap. Would recommend at least a welded muffler/glasspack I don't like press together but each his own.

cool man thanks for the info I just didnt wanna break something and yea your truck sounds poppin  :thumbup:

 

yea no more emissions for this truck lol ... i might just get some new headers as the stock ones lookin crusty and Ill be able to do egr delete easier and from there I can just 2 inch all the way back or somethin cool..

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Set the throttle cable so that when warmed up and idling (750-850) there is almost no slack in the cable. It should just be loose enough to allow it to return to idle. Then leave it.

 

 

The exhaust back fire is a result of ditching the stock set up for a weber and removing the muffler which lowers the sound. The stock carburetor has several devices to reduce eliminate the backfire... BCDD, anti backfire valve and fuel shutoff on deceleration. You'll just have to live with it.

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Set the throttle cable so that when warmed up and idling (750-850) there is almost no slack in the cable. It should just be loose enough to allow it to return to idle. Then leave it.

 

 

The exhaust back fire is a result of ditching the stock set up for a weber and removing the muffler which lowers the sound. The stock carburetor has several devices to reduce eliminate the backfire... BCDD, anti backfire valve and fuel shutoff on deceleration. You'll just have to live with it.

Yea i got the throttle cable pretty dialed now before it was so tight that when i tried to choke down after it heated up it wouldnt or i would have to fling the pedal hard and snap it back to idle down and it took me about 2 minutes to "retard" the cable so it had enough slack to idle down.

 

It would help if my tach was working..

I took out cluster and fixed my trip odometer but when i plugged it all back in tach refused to work.. didnt work before about half the time but it worked when i bought the truck... doesnt really affect me I feel confident in what the rpms are based on sound and from when the tach was actually working..

 

I enjoy it just dont want it to shit on me at 4k rpms deceleration which then i left foot brake and keep the throttle before apex to acceleraton i guess only way to describe it.. i only let it backfire when in 2nd gear cruising through town to get some heads turning :D

 

just wanted to make sure it doesnt effect the longevity of the motor.

 

I set my idle by having it warmed up. Ac full on and brights on and to the lowest point before the whole truck shakes from motor bog. Guessing its about 600-700 because when i set it higher the anti dieseling solenoid fails and the motor diesels when i shut it off at 800-1k rpms i think.. unless weber deletes that too haha

 

Oh i also did get a new thermostat (old one was stuck open) and now my temps are reading a little more higher but it might be slight cold but i think its ok because i got the lower temp TS (160??) Over the (180) and i think its ok because when climbing hills the ts will open sooner and prevent overheating. And at highway speed.

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  • 2 months later...

Alright just got in the mail my reg for my truck and turns out that it needs smog for some reason even though the last owner did it for me when i put the truck in my name a week after i bought it last year. So my options are selling it as-is. Going to a diff state. Attempt at a stock manifold cover. Or putting orig parts back on?

 

I have old carb and can get fittings and hose. My egr is still on the truck and i still have my vapor/gas canister. I would just need to rebuild carb which im confident I could do. Just worried about failing visual because of the fuel pump or there is one vaccum hose that I never chase down.

 

Any other ideas on how to get by this? I thought requirement was every other year in cali. I was not expecting this and my camaro just broke down on me so im relying on my truck a lot. I know its 2 months out but I need to see how to get through this to continue driving it in the future.

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[/url]">http://20180112_104212_zpscjqkw9va.jpg

 

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I think i finally figured out how to post pictures. hopefully this explains more what Im talking about lol. thanks again for the responses.

What a waste of time and money!

 

Put the stock fuel pump wiring and the steel "Y" pipe back in. Throw all the aftermarket/home made shit away.  The factory pump is a 3.5 psi pump and the steel "Y" creates enough back pressure through a metered orifice on the return line to keep the float bowl full at all speeds and fuel usage.

 

I do not know why you are making installing a Weber so hard and trying to engineer shit from house hold plumbing parts that are not gasoline rated.  This is a great way to burn you, your house, and your truck to the ground.

 

I have been running, working on, and installing Webers since the 70s and I have never seen such a pile of dangerous shit installed on a vehicle.

 

I hope that you are working with a Genuine Weber not a Chinese knock off.

 

Sorry if you can not handle tuff love!

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Alright just got in the mail my reg for my truck and turns out that it needs smog for some reason even though the last owner did it for me when i put the truck in my name a week after i bought it last year. So my options are selling it as-is. Going to a diff state. Attempt at a stock manifold cover. Or putting orig parts back on?

 

I have old carb and can get fittings and hose. My egr is still on the truck and i still have my vapor/gas canister. I would just need to rebuild carb which im confident I could do. Just worried about failing visual because of the fuel pump or there is one vaccum hose that I never chase down.

 

Any other ideas on how to get by this? I thought requirement was every other year in cali. I was not expecting this and my camaro just broke down on me so im relying on my truck a lot. I know its 2 months out but I need to see how to get through this to continue driving it in the future.

 

I feel your pain.... welcome to Kalifornia!

 

I need to do the head on my 720, almost afraid to put any money into the truck because they are desperate to always fail it.

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@charlie69 

 

Yea that was a long process and I only paid for the fuel line as I returned everything else because I work at a hardware store.. anyways I was trying to fix why it would fuel cut after 2 min of idling. thats why I rigged up some stuff just to diagnose .. Its fixed and I did put the stock y on and never used any of that brass plumbing shit in the truck... Turned out to be the mr. gasket fpr that I had replaced twice and I was chasing everything else down when my problem was right there..

 

Im not going back to stock pumps I went through 5 they would run for maybe a month and then click louder and eventually give out. (using holley fpr and fuel rated psi gauge to test up at carb)

 

 

unfortunately the mechanic who installed my weber origanally for me said it was a knockoff but idk how as the P.O. who sold me the truck paid $300 for it and it has genuine weber sticker on carb..

 

I should have just done the weber myself because after he installed it there were so many vaccum leaks that I was chasing down for a solid month. he used cheap rubber caps that would just blow off. I used brass caps on the intake to plug them and thats it.. but I wasnt confident in myself for the swap so thats why I had someone else do it.. now looking at it and seeing what was actually involved I am confident that I could put it back to stock myself with no issues. I just need the orig Hitachi rebuilt and intake fittings because I cracked all of them taking them out.. Im sure I could use brass fittings to make due because its just vacuum.. but im afraid that I wont pass visual and they will be considered "upgraded" because when I was doing smog on my 89 camaro I needed a tube from the exhaust heat shield to the air cleaner and had to buy 3 different exhaust hoses for it to be considered oem..

 

I still have 2 months to come up with something.. im considering just buying another parts truck thats z24 this time and is completely stock oem basic with a transmission problem or something so I can have visual representation and a whole set of parts. 

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You have definitely been persistant trying to figure out your fuel problem.  It is difficult living in CA and trying to keep older vehicles on the road.  I forget that the smog ispection is so involved there.

 

I agree with you idea to buy a stock parts truck to get yours back to stock for California emissions, much easier. if you need to swap plastic fittings on the manifolds ift is much easier to switch manifolds so you do not break fittings.  Before I pull old vacuum lines from plastic fittings I will spray the end of the hose with WD40, let it sit a while then I will take the end of the vacuum hose, then take my thub and index finger and gently queeze the hose at the end where it has the plastic barb in it.  Then I will twist the hose on the bard and work it off.  If the old vacuum hose is real hard I eill take a razor knife an curefully splith the hose on the barb.

 

When you change the intake manifold it is a good time to chack and or reolace the temp sender ans you have great access to it wiyh the manifold off.

 

Real Webers a have made in Spain on them and Weber is embossed also no stickers.  You probably have a knock off.  I will post pictures tomorrow of the marking on the real Webers.

 

Being in CA you can not run a Weber any way on the streets.  Captain 720 just picked up a 5 speed swap the came out ou my 85 ST king cab.  He also got the engine with it.  It is CA emissions and has the 6 wire feed back carb.  He might be willing to part with the carb and manifold.

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  • 2 months later...

So im going to rebuild the suspension while I put the orginal intake back on that I got from captain (thanks!) so I can do smog and have a nice ride instead of hearing squeaks and reduce steering play. Anyways I went with kyb shocks and I ordered and installed the fronts just fine (KG4605a) however the rears I would figure they would be the type with 2 round holes like my camaro where the bolts go through the side so I ordered (KG5473) off amazon and turns out my shock mount for my rear is like the front with a stud coming out of the top except for the rear it faces down? well the ones I got dont fit so I will return but I cant find the correct one to order? wondering if anyone can help me out on this and send me a link to rear 720 rwd shocks that have the stud rather than the round hole?

Edited by Toxicrain
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I am running the type you ordered on my 66 520 with the 80 720 2wd chassis.  I changed the bottom leaf spring shock bracket plates out with ones from a Datsun 710 goon.  This is because I lowered the truck with 4x4 720 springs but this only dropped it 2".  So when I have the money the 520 will go to the local spring shop and they will make new leaf springs as low as I want.  I will probably go 4 to 5 inches. 

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22 hours ago, DrvnDrvr said:

 

Thank you good sir!! i noticed this one says 2wd rather than the "rwd" i got originally.. 

20 hours ago, Charlie69 said:

I am running the type you ordered on my 66 520 with the 80 720 2wd chassis.  I changed the bottom leaf spring shock bracket plates out with ones from a Datsun 710 goon.  This is because I lowered the truck with 4x4 720 springs but this only dropped it 2".  So when I have the money the 520 will go to the local spring shop and they will make new leaf springs as low as I want.  I will probably go 4 to 5 inches. 

 Yea I want to find a pair of 4x4 leaf springs because they have less suspension travel(stiffer) for when I haul things like the 700lb 5.7l magnum motor I had to deliever. Rode about on the bump stops which are perfectly about a 1/4" away from fender which is nice ive never hit it. 

 

Ideally I want to c-notch and bag all the way around but I need to travel up to sacramento and find a shop willing to do it that I trust. for the moment Im looking to use belltech spindles with torsion bar the rest if needed whenever I find 15" rims or some 17" titans for cheap. and the 4x4 springs with a 2-3" block. I dont want to be completely slammed as I do want to be able to use the truck as a truck still but I will find that happy medium hopefully.

 

Thats all just idealistic if I can ever find those parts here before someone else snags them haha.. i also just did link kit and Im waiting for payday to get tierods and ill be able to do upper and lower ball joints tie rods and that should fix a lot of my steering slop(its about 90' turn before my wheels start to move) alignment after of course.

Edited by Toxicrain
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On the 4x4 leaf springs you have to flip the centering pin.  The 4x4 axles are under the springs and the 2wd is above the springs.

 

Be sure to clamp the spring packs on both sides of the centering pin.  I used welding vise grip clamps but a couple of simple "C" clamps will work fine.  I soaked mine with WD40 and still had to hammer them out using a brass drift.

Edited by Charlie69
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