Zed Head

TLTR - might be that that damper doesn't go with that degree marker. You have an early damper with a later degree marker/pointer. I'm not sure that zero is in the same place. Besides the fact that it looks like an old damper. And, on top of that, some of the early dampers were marked for a driver side pointer. If it was mine I would use piston position to verify zero. Since you have everything apart and in front of you. I can't find a decent picture of a 240Z marker out on the internet for some reason. I think I made AI mad and it's blocking me. I did find one old one though, linked below (site is in it!, and me!). It looks like the pointer used for zero with the notched damper pulley is right under the bolt head where with the later marker (yours) the bolt head is at 5 degrees. Don't know, just saying it's worth confirming. The guy in the thread also had a displaced damper apparently. Didn't get a final response.

No offende intended to site's rise to the top of an AI search. You just have to click the source links!

I think that "positive" crankcase ventilation came later. Where the system was designed to move air through the crankcase. They just called it "closed ventilation" before then. Meaning that the crankcase was connected to the air intake system instead of open to air. Anyway, wherever the exit from the crankcase ends up there will be oily gases at times. The pressure comes from blowby past the rings. Maximum pressure would be at high RPM, high load. So you'd want to estimate how much blowby you might expect. If you plug the big port then all of it has to pass through the small port in the valve cover. (p.s. core plug)

That's what he said...

Terrapin's diagram looks right. The label that says CARB is for that plugged port. As I understand things non-USA cars still used carburetors. Maybe there's a hose for them. Edit - and PURGE goes to full time intake vacuum. The larger hose with a nipple on the top of the intake manifold. The yellow dot goes to the ported vacuum port on the bottom of the throttle body. Which has a T that also goes to the vacuum advance canister on the distributor. Yours might be correct but people get them mixed up sometimes. Ported vacuum for the canister and the distributor. https://bringatrailer.com/listing/1975-datsun-280z-22-17/

Is this meta or ironic?

Don't know if this will help. L = bLue, BL = Black w/blue stripe, RW = Red w/white stripe, WB = White with black stripe. Notice that the blue wire is just passed through the ballast resistor directly to coil negative, using the stud as a terminal post. They could have just run it directly to coil negative. After blue leaves the diagram it heads off to the ignition module by the fuse box, and the tachometer. With the HEI conversion you wouldn't need the blue wire back to the cabin (module and tach) to make the engine run. But it is needed for the tachometer to work. You don't really need the ballast resistor anymore. You can find your power wires by turning the key on and measuring voltage, and by turnng the key to Start and measuring voltage. Those two should go to coil positive. The wirng diagrams can be confusing because sometimes they show connections that are just there for convenience. It helps to think about what needs power, and when it is supplied. I think though that Nissan also used one of the terminals as a connection post for AC clutch power. One of those "why is this wire here?" things. Might help to expand your picture and show what those green and white wires are connected to. What you're looking for might be buried in the harness. Those wires are not factree.

Not sure what this means (ball locker?) but the rust looks like a bad sign. There are needle bearings under the gears that would be sensitive to rust and crud floating around in the oil, maybe even rusted themselves. The hubs are splined so you could argue that the rust there doesn't really mater. The question is, what about the other parts? Are you tearing it all the way down for a rebuild?

Many people get caught by the Sorry looking dashpot nipple.

Should also say that it might be early to be buying an ECU. There are many possible reasons for the engine to die suddenly. Any loss of electrical power to certain components could cause it. I knew somebody with an 80's BMW that would do that. It was a fuse in the trunk that would get hot and lose connection. Took him forever to figure it out.

The chart is from a Nissan Technical Bulletin. It's in the Resource section, linked below. The differences between the ECU's is covered pretty deeply in that thread. Pretty sure that I commented about how I had tried a range of years (all of them, I think) of ECU's in my car and they all worked just fine. I was a parts collector, back when parts were abundant, and used my car as a testing unit. Probably worth remembering that the main point of EFI in the 70's was emissions reduction. Seems reasonable (to me) to assume that the minor changes were for emissions. Also worth remembering that some of the things that Nissan put in the FSM's and wiring diagrams didn't actually exist in the cars. https://www.classiczcars.com/files/file/16-ntb94-097-nissan-ecu-guide/ Here's a link to the thread again. (Those embedded links are easy to miss - hate 'em). https://www.classiczcars.com/forums/topic/60678-what-are-the-facts-about-280z-ecu-compatibility-and-differences/

Intermittent electrical problems are really hard to diagnose. I was testing a spare 1978 ECU and it did what you describe. Died, started right up, died again a half mile after, wouldn't start again. Had an ignition module that worked fine until it over about 3,000 RPM. Then the tachometer got weird, reading high and needle jumping around, and the engine ran poorly. Turned off the engine, restarted, and it was back to normal. All you can do is collect the clues and make your best guess.

I thought you were using an under the cap Pertronix, not a Pertronix branded HEI module. Those modules pass current through one of the mounting hole brass grommets. The thick one I believe, next to the B and C pins. The screw and the mounting area have to have a good ground.

There are two Pertronix Ignitors out there, I think, that will work with the Z distributors. One requires the ballast resistor or it might get damaged, the other has more modern current control. On the TIU, you can make any of them from 1975 to 1978 work if you don't use the second pickup coil in the distributor. I'd find a 78 version if I wanted to be close to original. But, really, I'd use the stock distributor and pickup coil with a GM HEI module. A modern ignition unit that's cheap and widely available. Might have been mentioned in a past post in your thread. Not sure. When you're optimizing your wiring, remember that there are two basic parts of the system - the triggering portion and the coil current portion. The strength of spark depends a lot on the coil current. You need full positive power and a solid path to ground. The path to ground is through the ignition module body, sometimes, which passes through the distributor body in the Pertronix application since it's mounted in the cap. The distributor has to have a good ground path so that the Pertronix module has a good ground. That's actually true for points also. Lots of options. Does it run yet?

I gave some parts from a thrashed 5 speed to @Terrapin Z quite a while ago, I think. If he's organized and labeled them he might be able to find them, if I did actually give them to him. I used the front case for a 240SX 5 speed conversion and kept all of the old parts. Can't stand throwing parts away. They might come in handy some day. If I didn't give them to TerrapinZ then I would have taken them to the metal scrap yard. A long shot.

That was spooky! What's up with the 240Z? Thought we'd be getting a few deep dive looks at how things work or how to make them work.

That's a weird one, especially since the fork position is different among the three. At least you found something. Since the 280Z 5 speeds are basically just the 4 speeds with an added 5th gear it makes sense that the 1-2 and 3-4 rods would be the same. BUT - the PartsManual says otherwise. Doesn't mean that the rods won't swap though. The change might be insignifcant. Edit - actually the part number is for the assembly, which includes the forks, which did change. Odds are in your favor. https://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-control/4-speed/from-sep-71 https://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-control/5-speed

Captain Obvious hasn't been around so I'll see if I can fill in for him: is there any chance that the rebuild guy just got the notches on the opposite/wrong side? 180 off? Each piece on the rods is held on with a roll pin. Part #7. They would be on the side we can't see in your pictures. On the inboard side.

This one doesn't look bad at stock height though. No reserve. https://bringatrailer.com/listing/1978-datsun-280z-22-28/

Stance matters. The 2+2 looks pretty good when lowered. Three way battle went on for a while. https://bringatrailer.com/listing/1977-datsun-280z-22-15/

Who rebuilt the engine? Was it rebuilt 17 years ago and parked or rebuilt after its resurrection? Are you a car dealer, selling on consignment? Looks nice. Good luck.

$20,000!

Might be a standard replacement. Here's what your 73 came with. Borrowed the picture from ZCD. Okay then, looks messy. Good luck.

This might help for ID marks. They're stamped on the back end. Also notice the size of the base circle, the part with no lobe. If it was reground the base circle wil be smaller. Yours kind of looks like a factory original cam. https://www.atlanticz.ca/zclub/techtips/cam/index.htm

I think that cgsheen1 and EuroDat are suggesting that drag, of some kind, is causing the shafts to turn in unison in your video in neutral, when they should be disconnected. But your earlier descriptions describes the engine stalling when it was in gear. That would be some serious drag. I'd still be studying the 4th gear hub and sleeve and synchro ring. If a different gear was stuck you'd get a mismatch between input and output shafts. The shaft speeds are matched. On the other side of the adapter plate 5th gear and reverse are on the same shaft. Reverse is just a whole gear moved to mesh with another gear. Non-synchro. 5th gear has a synchro. In the video you engaged reverse. Overall, everything points to a 4th gear being permanently engaged. As the coupling sleeve moves toward the selected gear it engages the synchro ring. The ring contacts the gear cone and friction causes their speeds to match. When the speeds are matched the sleeve slides over the teeth on the gear, transmitting force. I'll bet that the 4th gear synchro is stuck to the 4th gear synchro cone for some reason. Maybe it's broken. I am just exercising my brain, not an expert. But I do remember working on the puzzle in the past. I'd take a really close look at the interface between the ring and 4th gear. https://www.z-services.eu/en/internals/510-oem-synchronizer-ring-240z-260z-280z-280zx.html