Captain Obvious

First off, hopefully you already know this, but I want to make sure you understand that I wasn't chastising or anything with the wording. I was just trying to standardize on the language with what is in the FSM, etc. Sometimes with things (like the altitude corrector), the function is also the name and can help with troubleshooting. So no prejudice intended, and hopefully none taken. So I'm no expert on the BCDD device, but I do know they made several different varieties over the years that all did the same thing (which is limit the intake manifold vacuum at a certain level and not let it decrease below that level). Think of it as your air compressor outlet pressure regulator. Same concept. In 75 (and I think 76) they used that sideways lock screw to hold things in place, and in 77 and 78 they went to an external lock nut instead. Also in 78, they offered two different versions, one for CA and one for everyone else. The CA version was pretty much the same as they had been selling all along, but now starting in 78 the version to NON-CA cars was a simpler version that no longer included the altitude corrector. I guess they decided that other states didn't have enough altitude changes to warrant the compensator anymore. Point is... There might be some small variations between one and another depending on the year of manufacture. If both the units you have use the sideways lock screw, then they are both from 75 or 76 and should probably be pretty much identical inside (including the springs). Can you take a pic with the device disassembled and the parts laid out roughly in the position of assembly?

Matt, The two thin flexible rubber "gaskets" are actually called "diaphragms" and they are a little specialized. You can't just replace them with any simple rubber, so I would treat the originals gingerly. Just wipe as much of the oil off and reuse them. The third gasket (where the BCDD mates to the throttle body) I think is just regular gasket material and can be replaced with a home made version, but the other two cannot. The "adjuster coil" is actually a hermetically sealed air chamber that acts as a little barometer and compensates for changes in atmospheric pressure. Datsun called it the "altitude corrector", and it's meant to account for changes in pressure due to altitude. As for assembly, everything should be put together dry. In fact, there shouldn't be any oil anywhere in the BCDD, but as mentioned earlier, the oil gets there accidently (and probably unavoidably) through the PCV system. I don't think you can prevent all of it. Clean everything off, dry it out, put it back together, and hope for the best?

Wow, those are some fatties!! I've never seen anything like that before! Boiled peanuts are definitely a regional thing. I like them, but you never ever ever never find them this far North. People look at you with a complete blank lack of comprehension or disbelief. Sometimes even disgust. Every time I travel to far enough South, I eat some. My travelling companions think I'm nuts, but that's no surprise. So... A rock solid frozen bag packed in a little box made out of a couple layers of Styrofoam wall insulation would probably survive two days in the mail, wouldn't it? Build a little cubic foot hollow box out of the stuff?

Cool. I think the recommended way to handle it is to set the idle speed where you want it when the engine is warm, and then just deal with nursing the low idle until it warms up. That's how everyone did it in the "Ol' Days". Don't you remember the good old days when you just didn't even try to leave your driveway until you had sat there for a minute feathering the gas pedal to keep it running as it warmed up a little?

Is that a LED shop light you're using in that last pic? That's a really weird effect. Those multiple hard edged shadows give me a headache! Help meeeeee.... Please hellllp meeee!!

Right. All the cars have some way to purposely hold the throttle open a little more when the engine is cold. One way or another. On the 280's it's done with the AAR. On the 240's and 260's it's done with the cam on the choke linkage that pushes the throttle open a little bit. If you don't employ some technique like one of those, your idle will be lower cold than warm.

I would assume that all depends on where you set the temperature. I'm thinking I would want the temperature of the fan switch some token amount higher than the thermostat temp. If the system can operate in equilibrium without the fan running, then you are getting enough heat rejection from just natural airflow through the radiator. But if the temperature of the engine starts to creep above the thermostat temp, then it means the system has gone out of control and you have exceeded the heat dissipating capacity of the radiator (under the current conditions). And at that point, you need more flow. Either more water, or more air. If you are already maxed out on water flow (thermostat is all the way open), then you need more air. Turn the fan on.

Nice work! I've traced most of my carb problems to one of two things... Ham fisted previous owners screwing stuff up or sitting with gas in them for long periods of times. Or both! I've found that surgically clean and actually assembled correctly goes a long way to fixing a lot of issues! Go figure!! About that flat head screw... What are the chances that someone tried to create a ported vacuum source? Is that screw hole close to the butterfly?

Oh, and I forgot something... The oil weight in the carbs should have nothing to do with idle speed. Lean spot in transition off idle? Yes. But steady state idle speed? No.

I'll be the dissenting voice and say that I believe it is completely normal for the idle speed to increase as the engine warms up. All other things held constant, I think this is normal. I have a 280, which is supposed to have a device called the AAR who's purpose is to raise the idle speed when the engine is cold. I took my AAR off, so I have nothing to raise the idle. With no device to purposely bump up my cold idle, when I first start my car it idles a little low at 500. But then over the first ten minutes of warmup, that idle gradually creeps up to 750-800 as the engine becomes warmer and happier. Engines do not want to idle. And cold engines really do not want to idle. Unless I'm missing something here, I don't see the problem! Seems completely normal to me.

That's a great point. And I would go one step further and say that the sensor should probably be on the engine side of the thermostat. You know... the side with all the other sensors on it?

Sorry, but I'm lost. I don't understand all of the distinctions being made with the terms above. Duals Duals all the way to the back Twice pipes Split pipe I understand that all of these options eventually end up with two tips sticking out the rear of the car, but how many mufflers are used, and where does the separation between the two sides start?

I consider that a more philosophically complicated question. You're essentially saying "Everything in the car is new with zero miles on it except the odometer. With that in mind, should the odometer read the old original mileage, or can that be changed to zero miles as well?" I think the answer is "No, it should not be changed and it should reflect original mileage".

Well from what I heard, this guy's cousin is a pack-rat and has a file folder containing years of annual DOT registration records, annual state safety inspection records, and annual insurance documentation that all show the steady progression of mileage from when he purchased the vehicle until now. He can also answer the following questions completely honestly with his head held high: Q - Is that the original odometer in the vehicle? A - Yes. Q - Not considering any potential discrepancies which may have occurred without your knowledge and before your ownership, is the correct mileage of the vehicle what is shown on the odometer? A - Yes. Q - Are you sure? A - Yes. Q - Are you double dog sure? A - Yes. Q - Do you have documentation to prove it? A - Yes. Haha! I think he should be OK. Here's to hoping the DOT has better things to spend tax dollars on than pursuing that dead end!

Thanks guys. I added some clarifying detail to my original post.

I knew a guy, who knew a guy, who knew a guy, who knew a guy's cousin who temporarily installed a spare speedo in his car because the original was jumpy. The problem turned out to be the routing of the speedo cable and not the gauge itself, but before he put in the replacement, he took it apart and adjusted the odometer to reflect close to the correct mileage. He didn't bother with the 1's or 10's digits, but he changed the others so it was within 100 miles of my actual mileage. And then when he figured out that the speedo was never the problem in the first place, he took out the test unit and put his original back in. From what I heard, it's not too hard, but fiddly with small parts and the like. If you're good working on small delicate things, its not bad. If you're all thumbs and your best tool is a breaker bar or an impact gun, I'd send it to someone else.

Thanks in advance.

No. The only one that goes directly to the fuse box is the same one that goes to the alternator. The one that goes to the multi-function stalk goes to the fusebox after the switch. The two that go to the ignition relay go to the fusebox after the relay. The one that goes to the ignition switch and powers some stuff after the switch does not go to the fusebox at all (which I consider a design flaw). For example, the starter solenoid has no fuse in the line at all. Neither does the ignition module or coil. Now that we have identified the wiring harness year (probably? hopefully?) you can download that year wiring diagram and take a look. Here's a mostly finished color wiring diagram for 78: http://www.classiczcars.com/applications/core/interface/file/attachment.php?id=41454

Can you point me towards any documentation that describes the process? Or youtube videos of parts made using the same process?

Yikes. I can see why you bailed on the project. I sure do wish there was a cheap way to get a whole new skin on the dash.

The only thing missing is one of your dash retaining bolts. There was never anything installed in that "empty spot", It's simply a recessed area for one of the mounting bolts that holds the dash in place. There is supposed to be a bolt in the threaded hole that helps hold the dash. Yours is missing. If I had to guess, they may have used that location on earlier years to attach the hood release and vent control. But then they put in the lower valence panel and I think they changed how the vent and hood release are attached. Anyway, the only thing you are missing is a bolt.

How far into this process did you get? Were you thinking you would make the molds yourself, or were you looking for a company to make it for you?

Matt, I would be surprised if the bearings really needed to be replaced as it's not a high load application. Even so, I think pulling the whole thing apart is a good idea to clean out the gummed up crusty grease and make sure everything is working as intended. As for taking it apart, I'd be glad to give you a hand if you wanted to make the trip to my place. It's not as bad as it sounds.