New to the forum, beginner working on vehicles -- just bought a 1985 KC 4x4

[Zach]

Hey everyone, been browsing the forums for a couple weeks now. I bought a 720 with the hopes of bringing it back to life.

 

It's a solid truck, a little tired from age but I think with a little work it can be a solid daily driver.

 

Biggest things to take care of are...

 

- Carburetor, it idles poorly...I have a Weber in the shed ready to be installed

 

- Driveshaft (?) U joints were in rough shape, I changed them out but the truck still vibrates above about 35mph. I'm getting the driveshaft balanced. Picking up & reinstalling today, will see if the vibration goes away, hopefully that gets rid of it

 

- Rust in the floor pan on driver and passenger side, right around the cab mounts. Luckily it hasn't spread too much. I lifted the carpet and it was soaked. Got it drying right now, sprayed some rust converter on the floor for a temporary fix. I will have to cut the body mount bolts out, they're so corroded that the bolt has fused to the nut. Tried pb blaster and an impact gun, but the bolt head was so rusty that one try with the impact gun rounded the bolt head.

 

- It had factory A/C, but someone removed the compressor, so going to put a new one in

 

- Gonna flush and change all the fluids

 

 

Other than that, it feels solid. No rust on the frame, mostly just in the floors (hasn't spread too much which is nice) and in the bed. I'm going to spray in one of those Raptor bedliners after removing the rust.

 

So far I've been working on the driveshaft and tearing apart the interior to clean up, assess, and get rid of the rust on all the bolts / replace any that are too corroded.

 

I'll be around, all my questions I've had so far have led me back to this forum, so I'm excited to participate. Seems like there are some knowledgeable folks here.

 

[Zach]

Oh, regarding the cab mounts, is there a good source for replacements? I found some on eBay that are supposedly OEM equivalent -- link -- not sure if they're good quality, anyone have experience? Was also going to look into some universal ones from Energy Suspension, but the OEM front cab mount looks like a more unique shape, so not sure about that route either.

 

Since the cab mount bolts are so corroded, is anyone able to share what size bolts attach the cab to the frame? I'll need to replace mine.

[datzenmike]

 TTT

[powderfinger]

Great looking truck, exact same color as mine. Mine is also an ST. I'll try to post up a pick in this thread. Good luck with the vibration, I am in the middle of that nightmare right now. I took my driveshaft out, replaced the universal joints. Didn't fix it. Tried a second driveshaft I had, didn't fix it. Got the original driveshaft balanced from a reputable shop, didn't fix it. The entire time I was thinking that it simply had to be the driveshaft because of how it felt. Tried a third driveshaft, that I also had laying around lol, that mostly fixed it. It's at least drivable now but still has just enough of a buzz above 50-55mph that everything in the rearview mirror is fuzzy from the mirror vibrating which is annoying.

[powderfinger]

I have exactly what you need! Too bad I am not closer to you. I have a spare blue 4x4 with very low miles and a banged up passenger side. The floor pans look just like they did when it came out of the factory, except for one small hole that i was told was a hunting "accident" lol. I was planning to strip everything off of it that I want to keep as spares and ditch the rest of the truck. Engine and trans is already out. Frame is perfect as well. The truck only has 60k miles on it. 

[powderfinger]

Also sorry for so many replies, be careful trying to buy a compressor. It is difficult to find a factory replacement. If you order one you will likely receive one for a D21 truck. The site will say its for a 720 but they never are. Maybe you will have some luck finding one at a scrap yard or from someone on here that you can have rebuilt.

 

It's either that option or retrofitting a D21 compressor in which you will need some of the lines as well.

[datzenmike]

The rearmost drive shaft is a splined slip joint. Doesn't take much wear for it to get sloppy.

 

Vibration...

Damaged tire. Swap front to back see if any change.

Bent damaged rim.

Wheel weight fell off.

Broken leaf spring

Broken or loose U bolts.

Brake drum broken

Excessive drive shaft angles between transfer case and differential

Balance weights fell off drive shaft.

Engine, transmission or transfer case mounting bolts loose.

[powderfinger]

I would think you can tell if it's a tire or a potential driveshaft issue by the frequency of the vibration. That's how I figured mine main vibration had to be one of the driveshafts. The speed of the vibration was just too high to be a tire. Here is my truck before I took the led light off the bumper.

 

 

[datzenmike]

Exactly. The differential slows the wheels by a factor of almost 4 times. 

[Zach]

I actually figured out my vibration issue, it did turn out to be my driveshaft + u joints.

 

Had a lot of play in the u joints, replaced them, still had vibration, took it off again and had it balanced... now it's all sorted. Super smooth!

 

Currently working my way through Weber installation in between other life stuff. Got my old carb off, was trying to figure out which vac lines I need to keep with the new carb. Seems like I can remove all the old vac lines and just keep the one from the distributor? And it seems like I'll want that line to go into the carb? This is based on research so not entirely sure, but seems like that's the consensus. LMK if wrong. 

 

@powderfingerthanks for all the tips, I'll keep an eye on which compressor I end up with. I wish the old one were still in the truck so I could have it rebuilt.

 

Also I'd pay you if you were willing to remove the floor pans on yours and ship 'em to me. How are the seals on your king cab side windows (smaller ones)? If you're parting out and those are decent, mine are dry rotted and I can't find any replacements right now.

[powderfinger]

10 minutes ago, Zach said:

How are the seals on your king cab side windows (smaller ones)?

 

You will likely never find a set of these used in good condition. All of mine are pretty bad. VintageRubber now has a listing on their website for new ones but it currently says out of stock so not sure if they are planning to make more or not. I contacted them a year ago asking if they would make some. Didn't figure they would be $170 though lol.

 

https://vintagerubber.com/datsun-720-king-cab-side-window-seal-kit/

 

As far as cutting the floors out, sorry but I just don't have the time to do that.

Edited March 8, 2023 by powderfinger

[Zach]

No prob, figured as much, but thought I'd ask.

 

Yeah, I've seen that same listing, I emailed them but haven't heard anything back so may have to go another route.

[datzenmike]

You could run directly between carburetor port (the front most one) and the distributor vacuum advance. There is a  hose to the  TVV (thermal vacuum valve) but all that does is not allow vacuum advance to work until engine is warmed up. Ignore it.

 

One other thing you want to keep operating is the charcoal canister. It can also be piped off the vacuum advance. The canister stores evaporated fumes from the gas tank when engine is off. The vacuum line (when engine is running) operates the purge function and allows the intake to suction out these fumes and burn them. If disconnected there may be a gas fume smell. Cost nothing in performance to keep this operational.

[bigleagueteague]

What’s up Zach. I’m also a relatively new 720 owner. I just started up my own thread a few days back - BLT’s butter yellow ‘84.

My floor pans are also totally thrashed around the body mounts. Time to learn how to weld!

[Zach]

@bigleagueteagueyours looks great! I love that color.

[Zach]

Still working on carb installation, was wondering -- looks like the butterflies at the top don't fully open using the throttle lever, is that normal? They'll open all the way if i push on them with my hand, but the throttle lever at WOT leaves them about 3/4 of the way open.

 

Is opening them fully controlled by vacuum or temp or something? Or should the throttle lever fully open up the Weber 32/36?

[NC85ST]

54 minutes ago, Zach said:

looks like the butterflies at the top don't fully open using the throttle lever

Do you mean the choke? It opens as the engine warms up, unless you have a manual choke.

[Zach]

Oh! Okay, I see. I wasn't sure which ones were the choke. I'm trying to learn all this stuff as I go. Makes sense.

[iceman510]

 

On 3/8/2023 at 8:57 AM, powderfinger said:

Also sorry for so many replies, be careful trying to buy a compressor. It is difficult to find a factory replacement. If you order one you will likely receive one for a D21 truck. The site will say its for a 720 but they never are. Maybe you will have some luck finding one at a scrap yard or from someone on here that you can have rebuilt.

 

 

I have a compressor from an '81 2WD if it is interchangeable.  You may have it cheap if interested.  It is of course R12 originally, so factor that into your planning.

[Thomas Perkins]

Rock Auto has the compressor,but you need to change the hoses.My system was gutted and replaced.I use the same compressor as Rock Auto sells.

Edited March 11, 2023 by Thomas Perkins

[Zach]

Thanks @Thomas Perkins, was looking at the Rock Auto one.

 

I'm trying to fix a water leak, it's getting into the cab on the driver and passenger sides. I took the windshield cowl off and cleaned out a bunch of leaves and debris with a vacuum and an air compressor, but water is still finding it's way into the cab.

 

Is it possible that I need to remove the fenders? Where are the drain holes for the cowl found? Here are some pics of the leak:

 

 

 

 

Any other advice or experience with this type of leak?

 

[powderfinger]

Are you sure it's not coming in from around the windshield? It's pretty common on these. Could be under the cowl as well, that is also common.

[bottomwatcher]

I have the same leak. Hard to see near impossible to fix. I would pour some thickened epoxy in there only for the rust to continue and leak again. Pulling the fenders still doesn't give access. My plan is before my next paint job is to remove fenders and cut some access windows to fix once and for all then weld the windows back up. They do actually make plastic speaker grills that fit where your cardboard ones go. At least they don't rot and turn to mush.

[powderfinger]

15 hours ago, bottomwatcher said:

They do actually make plastic speaker grills that fit where your cardboard ones go. At least they don't rot and turn to mush.

Yep, the plastic ones can be found on the 86 models.

[Zach]

@powderfinger, @bottomwatcher -- are those grilles only a junkyard find, or is there somewhere online that sells them, too?