I just got a 720 king cab today runs like a dream. The only major things i habe found right now is the truck bed has some rust holes. Also it idles at really high RPMs every now and then it will be normal at around 1000, but most of the time its at 2500-3000 RPMs does anyone know the cause or if i am able to adjust anything to make it idle better. Also about the truck bed i looked and the majority of rust is on the wheel well panel on drivers side and back side oanel on drivers side would it be easier for me to fined a better truck bed from a salvage yard or does someone sell the panels at all. (i know the latter is a long shot)

Your idle issue may be a vacuum leak. Check all your vacuum lines and fittings; also check the carb and intake gaskets for leakage there. What year is your truck?

As for rust, there aren't any patch-panels that I known of for 720s, but there arethe occasional eBay listing for beds or panels from junkyards and such.
Welcome to the forums!

Cheers,
Peter

Its an 82 sorry i should habe mentioned that.

Definitely appears to be a vacuum leak then. I also own an '82 and had the exact same problems. I tested it by spraying brake-cleaner around the base of the carb, any changes in idle is evidence of a leak around that gasket. I have a Weber installed on mine and simply filing the surface of the intake and the adapter plate fixed my issues. Yours could be as simple as a cracked vacuum line though. If I were you, I'd look into removing all the unnecessary vacuum and emissions lines/equipment; depending on where you live, these smog-parts won't matter and you can also boost your engine performance and tuneability at the same time. Regarding the patch panels, another guess might be a local junkyard or pick-n-pull. Where are you located? I might have a few suggestions.

Cheers,
Peter

Im in OKlaoma City

Ah, not far at all! I'm just over in Lubbock, Texas. I will post a couple options in OKC that have older Nissan/Datsun pickups.

http://www.lkqpickyourpart.com/location ... 5/recents/
https://plus.google.com/108460487729481 ... bout?hl=en
http://riversidesalvageokc.com/about-au ... k-salvage/

Otherwise, let me know what other parts you need, I'll be running up to Oklahoma City later in the month and I could possibly bring some with me.

Cheers,
Peter

What thats awesome my wife is from lubbock will you be driving your datsun? As far as parts my wife put me on a budjet so right now im just wanting to get it as reliable as i can. This thing already runs like a beast except for this idle thing and the exhaust starts smoking a bit.

petercscherer wrote:Definitely appears to be a vacuum leak then. I also own an '82 and had the exact same problems. I tested it by spraying brake-cleaner around the base of the carb, any changes in idle is evidence of a leak around that gasket. I have a Weber installed on mine and simply filing the surface of the intake and the adapter plate fixed my issues. Yours could be as simple as a cracked vacuum line though. If I were you, I'd look into removing all the unnecessary vacuum and emissions lines/equipment; depending on where you live, these smog-parts won't matter and you can also boost your engine performance and tuneability at the same time. Regarding the patch panels, another guess might be a local junkyard or pick-n-pull. Where are you located? I might have a few suggestions.

Cheers,
Peter

What hoses am i able to take off. I also might be moving to Texas next year and i know they do emissions tests if that changes anything?

I will be up there in either my 720 or my 240z, haven't decided yet.

Regarding the vacuum lines, you can safely remove and cap-off everything except for the two vacuum advances off the carb/base.

As you can see in the photo, it really cleans everything up. My carb is a Weber, but the vacuum-advance lines are in the same locations on the factory Hitachi. Just those two remain, everything else can be removed.

In regards to Texas registration and emissions, all that they require is an annual inspection done by any lube-center or repair shop. They test all the lights, and then take it on a brief test drive around the block, if all that checks out, then the inspection sticker is issued. Super easy! So pulling these parts off are not going to void any testing other than if you live in California. I've also removed all EGR valves and exhaust re-breathers, but those require a bit more labor and don't really help too much.

Cheers,
Peter

Awesome im going to try this tomorrow or monday. How did you cap everything off?


I hope you drive your 720 would like to see it.

You can see the plugs in the manifold where some fittings were capped, I also used simple vacuum caps that you can purchase from any parts store. I'll see if I can find some before an after pics of what I removed.
~Peter

Alrighty, I'm not the supreme expert on explaining this process, but here's a few pics of what can be removed.


The "tower" in the front is part of the fuel-shut-off (an emissions/safety device from the 80's), it can be removed if you also pull the vacuum pump behind the carb. They are all part of the same system.

Everything that is circled was removed when I went through the engine. Those three caps on the carburetor were already that way when I got the truck and may actually be originally done at the factory.

Anyways, I'll include some other pics from other threads here to show more views of what can be plugged or bypassed.






The following thread was SUPER helpful for me and is also the source of several of the above images.
vacuum-line-removal-t556957.html

Good luck!
~Peter

petercscherer wrote:Alrighty, I'm not the supreme expert on explaining this process, but here's a few pics of what can be removed.


The "tower" in the front is part of the fuel-shut-off (an emissions/safety device from the 80's), it can be removed if you also pull the vacuum pump behind the carb. They are all part of the same system.

Everything that is circled was removed when I went through the engine. Those three caps on the carburetor were already that way when I got the truck and may actually be originally done at the factory.

Anyways, I'll include some other pics from other threads here to show more views of what can be plugged or bypassed.






The following thread was SUPER helpful for me and is also the source of several of the above images.
vacuum-line-removal-t556957.html

Good luck!
~Peter

In the diagram with the blue arrows are you able to use one of the original hoses to make that connection or do i need to get a new one? If i do what diameter is the connection so i know what size hose to get?

I was able to use the existing hoses. You'll notice a lot of excess hose after pulling the un-needed pieces off.
~Peter

Yes awesome ill keep you updated. Im heading over to a buddys today to help me.

Well we had a fun time getting this done, but we got it. We had to pull the hole carb out though because my buddy dropped his philips head bit fell in my carb, but thats all done and she pures like a kitten. Thank you so much for all your help. I appreciate it so much.

No problem, it's a real joy to help out other owners. Glad you're up-and-running! Post some pics when you get a chance!
~Peter

petercscherer wrote:No problem, it's a real joy to help out other owners. Glad you're up-and-running! Post some pics when you get a chance!
~Peter

I will if i can do it from my phone ill figure it out this week

how-to-post-pictures-using-photobucket-t521110.html

^That link will be helpful for uploading images.
~Peter

Peter, great work. Glad to have you aboard!

Well i think something else may be still wrong. I kmow they idle a little high warming up, but i feel like it stays forever. It has been idleing at 1800-2000 then it will drop to 800-1000 after about 20-30 min. Today driving it to work it stayed at the 1800-2000 then when i got to work it jumped up to 2500-3000 and was rough like before. Im checking the one hose today during lunch, but is there anything else i should check?

Did you check the nuts holding the carb to the intake? You also might be having an issue with the electronic choke actuator. These truck SHOULD idle at about 700-900 under normal conditions. It took me quite a bit of tuning the mixture and idle to get mine down to 750RPM. Your issue does still sound like a vacuum leak around the carb-base, since you describe very similar behavior to what I've experienced.

I can check the nuts after work. Now we noticed it is running pretty rich. We cant find the timing marks on the pully, my buddy thinks the timing could be out. I started it during lunch today and checked all our caps and it ran high starting out, then in maybe 10 min dropped to under 1000 RPMs real quick and then 10 min later it just died. As of right now it is idleing right its just running rich.

You'll probably end up leaning it out and then compensating with the fast-idle screw; timing is possible, but it wouldn't explain the change in idle speeds. Z-motors don't have Engine Control Units (ECU) like modern cars do, so once the timing is set, the only thing that changes is the vacuum advance. Running rich at idle is going to increase your idle-RPMs, it will also cause weird behavior once the engine is hot and can even cause vapor-lock in the carb.
~Peter

petercscherer wrote:You'll probably end up leaning it out and then compensating with the fast-idle screw; timing is possible, but it wouldn't explain the change in idle speeds. Z-motors don't have Engine Control Units (ECU) like modern cars do, so once the timing is set, the only thing that changes is the vacuum advance. Running rich at idle is going to increase your idle-RPMs, it will also cause weird behavior once the engine is hot and can even cause vapor-lock in the carb.
~Peter

Ok correct me if im wrong, from what i understand i set the mixture screw half way between dying rich and dying on the other side, and then i set the fast idle screw to compensate to a desirable idle?

Seems about right.

Ok here is what we have done. We moved the choke solenoid to where it was open all the time and it seemed to have idled better. We then started adjusting the mixture and idle speed screw. Now when the truck is cold it idles like a dream once warmed up it idles crazy either real high or real low then dies. I have tried adjusting mixture and idle screw when it gets to temperature, but it seems once i get it to a nice idle or as nice as i can while marmed up a mile down the road it starts idleing crazy again.

Well come to find out i got a sticky float. I should be ordering a weber soon!