New owners guide

[Foxhound]

Hello there folks, I just bought a 1984 Datsun/Nissan 720 KC 4x4 (non-cali emissions, 5spd manual) and thought it would be a good idea to lightly document the process for myself and anyone else who buys one of these bad boys. I'm new to this engine and older cars in general, but I would say my mechanical ability is intermediate and I have a passionate mind for problem solving and understanding how things work. This vehicle is slightly older than me if anyone cares. I'm also new to this forum and this is my first post. So far, browsing around here has been a great resource for useful info. I've learned a lot from datzenmike and others, thank you, and felt inspired to somewhat compile some of the basic things I've seen mentioned as well as go through the buying process and basic things to look for and maintain with this model/engine/transmission.

 

I'll admit there was very little that would have stopped me from buying this truck. I traveled 2+ hours to see it. It was exactly what I was looking for and it ran, drove, shifted fine. The body/frame was in good condition, original paint, very little rust. Interior was very nice. My original inspection wasn't as thorough as I would've liked it to be. Anxiety often gets the best of me in situations like this and I overlook or forget things in the moment. Don't be like me. You have the money, you're in control. Be thorough, have a checklist. For example, rather than looking inside the coolant reservoir, I just looked from the outside. Upon getting it back home and really inspecting it, what I thought was coolant was just a dried up line of crust. Slapped myself for that one. I know better too, but in the moment when you're chatting with a complete stranger and trying to inspect things, it's easy to lose focus.

 

The truck: 180,400 miles. z24 engine with a FS5W71B transmission. 6 owners 😅 (I know one of you's is on this forum!)...so she has her quirks. For starters some mice had gotten in the engine bay and chewed up some wires, mostly on the passenger side of the engine bay. Most wires had been replaced/repaired a little janky (speaker wires to fuel pump as an example). I suspect these wires may have something to do with why the tachometer and oil pressure gauge aren't working. The seller also disclosed that the front seal for the crankshaft was leaking. Upon further inspection at home, I think the leak is actually from a small crack where the oil pump bolts into the timing cover (possibly over-torqued), very close to the seal. I'm not going to worry about this leak for the moment and just keep a close eye on it because I really don't want to take the timing cover off just yet. I will put a new seal in tho just in case. My main goal is to refresh all the fluids, and replace some basic parts so this can be a reliable work truck until I can dig deeper into the engine. I seriously considered getting down to the head gasket, but I don't think I have the time for that right now, we'll see. The truck is also dieseling (running after the truck is turned off for those unfamiliar with the term like I was). The seller said he thinks the timing needs to be adjusted which I planned on doing.

 

The drive back was smooth. I've never owned a manual, but I've had enough practice to feel comfortable driving one. Only stalled once, but made the mistake of downshifting to 2nd while trying to upshift to 4th. I was so focused on NOT shifting into reverse by accident. What's done is done, hopefully it didn't stress anything out too much. It engine braked for a couple seconds before I pushed the clutch back down and put it back into 3rd. No weird sounds. Everything seemed fine after. The only other things I noted on the drive was it seemed to be running hot even though the temp gauge never got above halfway and it lacked a little power uphill, but what do I know. I got it to 70mph on the highway. I didn't want to push it further.

 

So far I've pulled off the hood, air filter housing, distributor cap and wires, battery, valve cover, and the radiator/hoses. Nothing crazy yet, this is about as much disassembly as I want to do right now.  I mainly wanted to check out the timing chain and set the valve lash when I put things back together. Also to check and re-torque the headbolts as has been mentioned here many times because it's the leading cause of head gasket failure in the z24. I forgot to check compression warm before disassembly, so I just checked it cold on the exhaust side for now because why not. Front to back - 170psi, 170psi, 165psi, 165psi. The sparkplug on the intake side for cylinder 3 was suspiciously difficult to crack loose. Sparkplugs are also bosch which I'll be changing to the NGK BPR6ES (intake side) and BPR5ES (exhaust side) as per recommendation here. The timing chain felt loose at first on the driver side, but turning the crankshaft a bit clockwise tightened it up. I'm not sure how much slack I should have here. There are slight scuff marks on the outside of the chain. I know these are interference engines and I want to be extra cautious with things involved in timing. The guides look good, nothings broken or chipped looking from above. Is there a way to check that the tensioner is functioning correctly without taking off the cover?

 

The oil I drained was very old and grey looking, the oil filter was a FRAM, tisk tisk. I want to change the oil pressure sender too, but it is proving to be a pain in the arse. I suspect it's the original from 84. I thought I could just unscrew it by hand like the oil filter, but the casing spins separate from the threads. The nut behind the casing is in such a tight space beneath the intake manifold, it's hard to get any leverage. So far the only engineering that's rubbed me wrong. Really don't want to take off the intake to get it loose. I could use some recommendations on oil. The seller was using straight 30 semi-synthetic. I didn't question him on it. He seemed like a mechanically inclined older fellow. He owned the vehicle for 3 years and put 4000 miles on it. Probably changed the oil when he got it and didn't touch it. Mostly used it as a winter driving vehicle. A little worrying to me to use straight 30 in the winter, but again, what do I know. Don't question the elders.

 

Same story with the coolant, very old and dark. There is a "new" water pump and fan clutch installed. Someone used RTV red to "help" seal it when they did the gasket. Not comforting. I've only heard of using red for exhaust. Last thing I want is excess rtv pieces clogging up coolant passages. Definitely flushing with distilled water (not sure if I should use any flushing products, probably not). The thermostat looks pretty old, putting in a new one. Radiator cap gasket was in rough shape too, a new cap is cheap enough. Going to change the temp sensor as well. I suspect its beneath the carb? There was some other electrical sensor(?) beneath the thermostat with only one green wire connected to it. Not sure which is what. I'll be refilling with Zerex coolant for asian cars unless there's a better alternative.

 

I'm also fairly new to carburetors. I'm not going to rebuild or mess with this one (stock) yet until I have a better understanding of them. I see there are two electrical connections going to it, one blue wire for the choke I'm assuming and one looks like some kind of airflow sensor (black and yellow wire)? I'm under the impression there is no ECU. Is there any other type of computer or programmable thing I should know about? I've been looking into the Weber K646 32/36 after some research, but I won't be changing until I decide if I want it to be able to pass smog or not, probably not.

 

I haven't drained the oil for the transmission or differentials yet, but they are on my list. For the tranny: YELLOW-SAFE GL-4 80w90 seems to be the go to. And for the differentials GL-5 80w90. I've heard the main thing to look out for in these transmissions is the counter shaft bearings. Any tips for looking into that would be helpful.

 

Well that's about where I'm at right now. I've also ordered an original repair manual specifically for this year and model. I'll post updates and pics as I go. Happy to be part of this niche little community. Cheers and thanks again

 

Some pics: https://imgur.com/a/WBVkbd3

https://imgur.com/a/kX90PS6

https://imgur.com/a/3GiJvVE

 

 

 

 

[datzenmike]

Sounds good.

[bottomwatcher]

Nice looking truck! You have done your research. That was a lot to take in which was good and detailed. When you do come back to ask questions try to do it one question or one system at a time. Things can get confusing here pretty quick. The only thing I saw missing was to swap in a fresh fuel filter on the priority list. Good luck and keep us posted on progress.