Newbie with a 74 620

[meatmuffin]

I just "inherited" a 1974 Datsun 620 with an automatic (meh) transmission.

I don't have pics right now (I'm going to pick it up this weekend) but had a few questions to get me off the ground.

 

Disclosure: I don't have a ton of experience with cars. I can identify major parts by name but I'm coming from a beginner's standpoint. That's a lot of the reason I decided to take on this car is because I figured it would be a good way to learn. I don't "need" it to get around town (this is the first time I've had a car in two years) but I would like to get it into safe, functional condition.

 

The previous owner (dipshit cousin who owed me money) did a decent job maintaining the engine, fluids, etc. All the hoses look relatively new, fluids are clean, etc. However, it has problems:

 

- It runs smoothly but idles rough and threatens to stall when I'm at a long light. It sounds/feels like it's not getting enough fuel. I'm pretty sure this is a carb issue - it has the original carburetor. Pretty much everything I've seen says swap it for a Weber carb. Is this a doable project for a newb with the tools, time, and space?

 

- There is a small oil leak on the passenger side of the engine. It looks like it's that oil pressure switch (sensor?) problem. The engine is clean so I could see the origin point and it's not a consistent leak, just an ounce or two on the floor when it's parked. The swap out seems pretty straightforward but by doing it myself am I risking totally effing it up?

 

- Rust! This is where I am really confused. We're in the Southwest, it's been parked here it's whole life. The rust is pretty much isolated to rockers and floor pan but, unfortunately, the only spots on the floor pan that are rusted through are around the cab mounts. That being said, the frame is rust free which is surprising. There's also a bunch of bondo or some other crap that either my cousin or the owner prior to him (I'm #3) glopped onto the mount where it meets the pan.

 

The only reason I agreed to take the car in lieu of payment with this issue is because otherwise the frame and body are pretty much rust free. It's just these four points. I also have experience with metalworking (I work for a sculpture artist) so the idea of welding a patch panel doesn't freak me out. From underneath the mount looks okay, where it meets the frame is solid, but the bushings all around are going to have to be replaced anyways.
That being said - what the hell do I do about the bondo? Thankfully it's just the one mount that got coated in that crap but the bolts are already rusted to hell, I'm worried about being able to get them off to replace. Could I, while the cab is supported, just cut out the section of floor pan surrounding the mount and get to the bolt from underneath? Since I'm going to have to patch anyways? Any advice from someone whose done this repair before?

 

- The wiring is a mess. I have no idea what is going on with it and the dash is super trashed. While this is mostly inconvenient and ugly, there are some real wiring issues that I need to deal with before I try to drive - the brake lights and turn signals don't work. Because the PO did such a hack job and decided to brilliantly paint the coated wired black (I can scrape it off to find the original color but really? Who does that?) I can't tell what is what from where or why. I've been thumbing through the service manual for the year/model but it's not really a "layman's" guide to wiring. Would a Haynes manual be worth it or is there a better resource out there?

 

LASTLY - I want to take this car to a mechanic before doing any of this because I have no idea what I'm doing. The thing is, I feel sort of ridiculous owning a car like this without a real working knowledge of cars (the most advanced thing I've done is change my own brakes and a caliper once, because I was way too poor to pay someone else to do it). The car needs an oil change anyways and I figure it's a good intro, I've just had terrible experiences with mechanics in the past. They always treat me like I'm an idiot (note: I'm a chick) and try to rip me off, or are condescending when I challenge them on their bullshit. I got this car specifically because it's a skill I want to learn. Also because it's badass. Do you have any advice on finding a non-judgmental mechanic who would be willing to give me advice?

 

I'll get pics up as soon as I get it down to my house.

[datzenmike]

Learn to do stuff yourself. For a few hours you pay a mechanic you can get most of the tools you will need for most fixing projects. Learn as you go and buy tools as needed. Most mechanics today have no experience on carbs and a 40 year old truck so why pay them to learn????? The Haynes manual for the 620 is super good for the wiring diagrams. Not bad for the rest. About $20. The '72 620 FSM factory service manual, is the bible and covers completely all facets of your year of truck. About $80 probably a lot less on E Bay.

 

The oil sender is about $8 at any auto parts store.Make sure you get one for a Nissan because this is the only part on a metric truck that has British Pipe Threads on it. Just loosen and unscrew the old one and screw in the new one.

 

As to the carb don't throw out yet. Not without making a few adjustments and checks. At least get it running better while you wait for a new weber, And by new I mean a NEW one from Weber that is a direct replacement for your year L18 truck.

 

Check the valve adjustment or clearance. You need a couple of wrenches and a feeler gauge. You just saved yourself an hour of mechanics rate.

 

Borrow a timing light and check set the advance

 

Now set the carb idle mixture and idle speed

 

In this order. Now it will get you around better.

[meatmuffin]

I definitely want to do the work myself, the parts are all so cheap it feels like throwing money out the window to get a mechanic to do anything. I'm just learning and need to have patience I guess. Thankfully I have access to a lot of general tools so I can probably save some money there, at least to start. 

 

I downloaded a copy of the '74 Factory Service Manual - is there an advantage to the '72 one? 

 

Is it possible to do a front disk brake conversion on these suckers? I vaguely remember reading something about it being a total pain because of the kingpin. This is something I would save for later on in the project, I just want to keep it in mind going forward. 

 

As for the crappy/rusty mounts go - there's no big gaping hole around them but it is pocked with little (dime size or less) ones. The bushings are totally weathered through (I'm guessing this is why the cab is ~ 1in lower than the bed level atm). I wanted to take her to the mountains to go camping next weekend. Assuming that the lights and engine are in good working order by then would I be risking any serious damage to the frame or body as long as I stick to the highway? It seems sound enough to handle it but I've heard horror stories. 

 

Thanks for the help! I'm excited to embark on this endeavor. 

[ggzilla]

The 1972 manual will have wiring diagrams and engine specs for the 1972, which is quite different. Buy one at Amazon.com.

[MikeRL411]

Oil sender adapter is Autometer 2269, just so you don't waste a half hour while the parts counter gains a piece of esoteric knowledge while you wait.

[ggzilla]

Why buy an adapter? It is not needed when replacing the sender.

 

Nissan part number 25240-89910 SWITCH ASSY-OIL PRESSURE $17 USD

 

$3 at RockAuto

Beck/Arnley 201-0262

[meatmuffin]

The manual I got from here:

 

http://www.davidcmurphy.com/olddat/620tech.htm

[datzenmike]

Your '74 saw a lot of changes than those years before. First and only year with L18 motor. First year with the new 4 speed transmission. All emissions equipment and wiring is year specific. Get the '74 manual if possible.

 

Type "front disc brake into 620" into our search engine upper right of every page and start reading. There are members here who make kits.

[meatmuffin]

Yeah I noticed a lot happened between 73 and 75 for the 620, any idea why they decided to run the L18 engine for just the one year?

[datzenmike]

More power than the L16 and the L20B wasn't ready for the truck. N America loves bigger everything.