Captain Obvious

I'm no expert on the chronology of what Datsun did when, but I have high confidence that your car originally had four-screw round tops installed from the factory. I don't believe the three-screw round tops came out until the 72 "model year", and the Datsun parts manual supports that belief... Four-screws until 8/71 and three-screws from 9/71 until they went to the flat tops in 73. So, that said, I think the four-screw carbs would be the original version for your car. Ztherapy's question about the intake manifold is also something to look at... What number is on your manifold? An E46 is 4 screw, E88 is 3 screw." There should be a part number cast into your intake manifold runner. If that number is E46, then it would have originally been paired with 4-screw round tops. And if that number is an E88, then it would have originally been paired with 3-screw round tops. Of course, at this time, who knows what kind of mix-n-match of parts is on it at this point. Bottom line? For originality, I think you should be running four-screw round tops. But the pair you have pictured have drains on the bowls (which I think is not original). Do the bowls on the installed 3-screw carbs have bowl drains? They should, but if they don't then someone probably swapped the bowls from one pair to the other?

Black oval head Phillips.

That style (without the Phillips feature) was used through at least September 1970. VIN around 10000. I can attest to that with personal experience.

I do not believe that one in the auction is correct for an early car. My (limited) experience indicates that the original did not have a phillps feature in the center. I suspect that one on ebay was originally used in the hood bumper location, not the gas pedal stop. That said, it struck me as very Un-Japanese to use different parts in those two applications, so I wouldn't be surprised to learn that somewhere along the way they standardized on the same part in all three spots. But I believe on early cars the two hood bumpers had the Phillips feature, while the gas pedal stop did not.

Yes. Different shape, but yes:

I was there for ZCON, but CO is a little far for an off-duty house call. 🙂 So you're bailing on the injector thing and ordering a different set that has a better past reputation? I'm currently interested in hearing and investigating injector issues as I'm planing to mess with them here in the not too distant future. With some of my favorite humans:

I'm just having a hard time believing that all six of your brand new injectors are dead on arrival. That's why I'm searching for a different answer. Where are you located?

I'm thinking that maybe, yes? I wouldn't be surprised to learn that new injectors with a different internal valving system are quieter than the old original pintle style. The more motion there is inside the injector, the more things will wear. Minimizing the motion would minimize wear. Maybe the new ones are actually opening, but just really quiet. You can test to see if they are opening using a can of carb cleaner and a straw.... Connect the injector to a power source (I've heard that a nine-volt battery works and runs less chance of damaging the injector) and then while there is power on the injector, you can spray a blast of carb cleaner through the injector. If it's open, it'll come out the other end. If not open, it wont. Note: Wear safety glasses.

Are you sure the new ones aren't clicking? Maybe it's a faint click that is hard to hear? Can you try connecting some of the new injectors directly to the battery with jumper leads and see if they click that way? Don't leave it connected for too long because it might not be good for the injector. But you should be able to touch the leads to the battery for a quick test without hurting anything.

I remember that thread from the other forum: https://www.zcar.com/threads/1983-280zx-with-weird-injector-problem.427586/ I watched that thread as it developed, but never got involved. I'm not sure I agree with their conclusions, but I certainly cannot disagree with their results. In that thread, they noticed that if they disconnected one (or sometimes maybe two?) injectors, the remaining injectors would fire. Did you have that same result? Or do yours never work?

If it's all three back injectors, it might be an ECU issue. The ECU controls the injectors in two groups... 1-3 and 4-6. Might be a problem with the circuit that drives 4 through 6?

Those look good. Nice job!

The reservoirs being over filled is a red herring. No effect on how the pedal feels. Let's hope it was air in the system that you got out!!

The FSM says mil-prf-10924 grease, which a quick look on the web indicates it's a Lithium complex base grease. It should apparently comply with the following: "a. Work a sample of the test grease on a motorized grease worker for 100,000 double strokes (approximately 28 hours) in accordance with the procedure described in ASTM D217 for prolonged worked penetration. b. Immediately after the grease has been subjected to 100,000 double strokes, bring the grease worker and the sample to 25 ±0.5C in accordance with the procedure described in ASTM D217 for prolonged worked penetration." So whatever you use, make sure it can handle enough strokes and produces appropriate penetration. Reference : https://chemsol.com/wp-content/uploads/2013/10/MIL-PRF-10924.pdf

I'm sure no chemist, but I think almost all solvents work better when warmer. So warm solvent would pretty much always work better than cold solvent? I'd be a little careful with stuff around aluminum though. Last time I cleaned up a set, I used hot water and Dawn dish soap in an ultrasonic and a stiff plastic bristle brush. I don't know how much the US brought to the party... Most of the cleaning effect may have come from the hot water and soap and the brush.

I'm sure this would be available from generic sources and I'll measure an original pilot when I get a chance. Are you thinking you want to use that roller option? If so, I'd advise against it. Might just be my conservative nature, but I see more downside than up. In the meantime, I do have this from sometime past:

The way the shoes expand is the adjuster lever arm grabs a tooth on the geared wheel when you pull up on the hand brake. But when you release the hand brake, the lever slips across the geared wheel without turning it (because of the shape of the teeth on the wheel). Keep yanking the brake lever up and then releasing, the shoes keep expanding one tooth at a time. UNTIL.... Once you reach the point that the shoes are spread far enough that the lever travel is so short that it does not catch a tooth when you pull up on the handle. At that point, the wheel will not turn any more until the shoes have worn enough that the lever travel will grab a tooth. That's the mechanism that keeps the shoes from wedging themselves in place.

Here's some reading that might help. https://www.classiczcars.com/forums/topic/21910-76-datsun-280z-throttle-sticking/page/2/ https://www.classiczcars.com/forums/topic/45152-sticky-throttle-body-hanging-idle/ https://www.classiczcars.com/forums/topic/57126-sticky-throttle-body-fix-delrin-bushings/

If you can blip the throttle and the idle returns to where it belongs, then the issue has nothing to do with the BCDD. That kind of hanging idle is a mechanical issue either with the linkage, or with the throttle body itself. I had that problem with my 77 and after lots of investigation and changes, the only thing that fixed it was to switch to a completely different throttle body. I ended up adapting a Sentra throttle body and adding a cable linkage. Bunch of work, but it's smooth as silk now. And I'm near Philly. Lancaster is about an hour and a half from me. Depends on the traffic (which is often terrible for some unexplained reason!)

Yeah, the BCDD can be troublesome. First thing to try would be to confirm that's the issue. If it's not all messed up inside, you can hopefully adjust to solve the problem.

The hanging RPM's might be because of the BCDD, but it has nothing to do with that vacuum line. In fact, that vacuum connection has nothing to do with the BCDD. It LOOKS like it has something to do with the BCDD because of it's close proximity, but inside, it makes absolutely no connection to the inner workings of the BCDD at all. There are two vacuum ports on the underside of the throttle body: One of them is a ported vacuum source that supplies vacuum advance to the distributor under light load conditions. The other is a ported vacuum source used to actuate the EGR system under light load conditions. If you aren't using the EGR system, you can cap off that ported vacuum nipple, but it won't (shouldn't?) do anything to change your hanging RPMs. But if it's hanging open, you should cap it off.

Haha!

Well then, I suggest that maybe you've never actually experienced a damper that is working correctly. Either that, or I've got delicate soft fingers while you've got rugged manly-man lumberjack hands. 😀