Zed Head

That's a good point Cliff. I glossed over the fact that the TPS was connected before but is not now. Having the TPS disconnected would be like having the throttle pedal partially open. No idle enrichment and no full throttle enrichment. According to the FSM. Not clear what "bypassed " means though, above. Another switch that might be disconnected is the AFM plug. Not uncommon for it to fall off as you're trying to get the AFM plugged in and back in its hole. Really at this point it would be a good idea to go through the electrical tests in the EFI Guide Book. Lots of other stuff that could be unplugged and affecting things. Coolant temperature sensor, for example. Electrical tests here. Good practice with the meter. Nissan has some weird formatting in the FSM.

Try to find the glue blob marks and put it back exactly where it was. The only reason to adjust the AFM is to fix the last guy's adjustment. I assume by calibrating with weights you mean the atlanticz procedure? http://www.atlanticz.ca/zclub/techtips/afm/index.html

I've never had my ignition timing off by much but I do know that when it is advanced idle RPM goes up and when it is reduced idle RPM goes down. I did have a situation though on my first car where timing was so reduced that the engine would barely run. Beside that though, ignition timing that is off by a lot can cause engine damage. Reduced timing can cause overheating and advanced timing can cause detonation. So it's very important to have it correct. As far as your specific problem just keep in mind that, generally, the engine will rev as high as it can for the amount of air that is supplied. A thought that just came to mind is that maybe the AFM vane is stuck or sticky, blocking air flow. You can pop the black cover off of the side of the AFM and watch the counterweight move as air flow rate changes. It should move easily. You can also affect the fuel-air ratio by moving the counterweight which will move the vane. The farther open the vane the more fuel the ECU supplies. The cover is easily pried off it is only held on by a tight fit and maybe a few drops of sealant. And, don't overlook the not uncommon mistake of leaving a rag or paper towel somewhere that it's not supposed to be.

No offense, but NO, not even close. Actually, that is close, the starting point, but not close enough. You need to finish with a timing light. Here's a video showing how to set ignition timing. It's very important. This one covers the basics without a bunch of fluff.

You're saying that the problem is fixed now? Did you order the wrong product or did the wrong nuts get put in your package?

Using a timing light to see that the mark on the damper pulley is correct in relation to the marker on the front cover. Sometimes timing can be so far off that the engine just won't run right. This thing... Picture from here.

p.s. once the engine is running things like the coil and relays and fuel pressure become less significant. Ignition timing is important though. Have you confirmed that?

Since letting a little more air in through the AFM doesn't increase idle RPM that seems like a sign that you might have a big vacuum leak in the intake system. The engine needs a lot more air through the AFM to add more fuel. Unmetered air leaning things out so that the engine can't run. Do you have all of the PCV hoses properly connected and sealed? A picture of the engine would tell more than a picture of the car. Looks like fun. Also possible that you're not adjusting the correct screw.

CO mentioned valving. I looked around and found a mention of residual pressure valves. That could be a reason. I think that the topic has come up in past discussions, I had forgotten about it. You can hold pressure on drum brakes because there are return springs. You wouldn't want that on the front. Makes me realize that it could be a possible cause of dragging brakes, mixed-up lines. Makes you wonder though if the quality level of a reman master cylinder is really up to the level of controlling residual pressure. Another neat test bench factor to consider. Or just do F and R. "tandem master cylinder" is the search term to use. http://www.britishv8.org/Articles/Tandem-Master-Cylinders.htm "Another issue when selecting a tandem master cylinder is whether it comes with one or more internal residual pressure valves. On an OEM master cylinder designed for a car with rear drum brakes there will sometimes be a residual pressure valve in the rear brake circuit to maintain a small amount of pressure at the wheel cylinder seals. The amount of residual pressure varies from one design to another but typically is between 6 and 25psi. Disc brake calipers may or may not need a residual pressure valve depending on their design. A 2psi residual pressure valve is often recommended for aftermarket disc brake calipers."

I looked in to cavitation a little farther and also came up with aeration. This would be caused by a leak in the suction side of the pump. The pump is above the level of the oil so you need a solid column of oil in the pickup tube to keep the pump full. If there's a leak in the tube or at the pump's suction side it will pull air in along with the oil. So, you could have an obstruction or you might have an air leak. Not sure but you might be able to rig something up at the oil pump inlet to see if the tube is pulling air along with the oil. I don't have a mental image of what would be involved there. Pretty interesting stuff. https://www.machinerylubrication.com/Read/30768/cavitation-or-aeration https://www.machinerylubrication.com/Read/28767/gear-pump-cavitation

Might help to have an illustration of the oil path to ponder. Pressure is caused by resistance to flow. Flow starts at the oil pump. You said that you installed a new oil pump, but who knows about its quality. The oil pump has a relief valve that could reduce pressure. The oil filter area has a relief valve but flow will still be resisted by the main bearings and the restrictor at the supply to the head. So that bypass doesn't really matter. Hard to know how much oil could pass through that restrictor to the spray bar. I think that I saw it in one of your pictures. And, apparently, some engines have another supply passage to the head at the front. It's not shown in the illustration but I have a vague memory of reading about it. A thought that just occured - the fact that pressure reduces at higher RPM might be caused by cavitation. Which could be caused by a restriction in the supply to the pump. So, it kind of circles back around to the pickup tube. Maybe you got a gasket on backward or something. The pump just moves volume. Pressure is caused by restriction.

Actually, the hydraulics of the system mean that both ends get the same volume for the same amount of stroke. Might just be that the F and the R are there so that the mechanic knows where to put the reservoir.

It would be fun maybe to set up a bench testing unit to move fluid in and out of some sort of device. Maybe some graduated cylinders so you could see the rate of flow. I wonder if there is some sort of service bulletin out there with some words about the switching of the reservoirs. Maybe something in Wick Humble's book or one of the others. I don't have my books handy. Nissan's FSM's usually have short explanations for the functions of the various components. This is all I find for the 1972 master cylinder.

It's in the thing...

Here's a red one that made it to $35,000 in November of 2020, but did not sell. Not sure the market is better now. https://bringatrailer.com/listing/1971-datsun-240z-253/ https://bringatrailer.com/listing/1971-datsun-240z-159/

I'm not sure it matters though for function. It's just a bigger reservoir.

Here's the drawing from the 1972 FSM. It shows the big reservoir up front and shows the lines through the warning switch. No drawing number though. This from the very same chapter. Seems reasonable to guess that it's an old picture from 1971.. BUT, I opened up what is supposed to be the 1971 FSM and it shows this.

Is this the current problem? Or is it still doing this? Can you summarize what you're trying to fix now?

Don't forget valve lash. It's the very first thing mentioned in the tune-up chapter. Very important.

It might be the typical "lean" problem with the EFI systems. You can add resistance to the coolant temperature sensor circuit and fix it. Link below. It could also be clogged injectors. When I got my car it had been sitting for a while. The injectors were unbalanced, some were under-squirting by quite a bit. http://atlanticz.ca/zclub/techtips/tempsensorpot/index.html

Your picture is the warning switch right? Anyway, looks like fun.

The 75-77 models have a screw panel for the connections. 78 is the only one with the plug connector. I think that all of the plug connector Z ignition modules are the same. The eBay price is stiff competition though, compared to what they used to go for. The picture looks right. Wonder where the warehouse of old new ignition modules was, that these Spark people found.

I had another thought about the brake check warning lamp switch. It could allow a transfer but I don't know why it would be one way. My first post was on target I think. The seals push one way and let fluid slip past the other way. Easy to check. Good luck.

The ignition module is by the fuse box. They're expensive. I found an eBay ad with a picture but I have no idea where these guys would get new modules. Also don't know if the electronics still age when not used. Don't get carried away. Only posting this for the picture and for anyone else who might need one and want to take a gamble. Seems too cheap to be true. Put "NEW - OUT OF BOX Ignition Control Module For 1978 Datsun 280z 2.8L S30" in the eBay search box. https://www.ebay.com/

Seems like the front seal is installed backward, or one of the middle seals. It's pushing fluid from the front of the cylinder to the back on the return stroke. Easier to imagine with a picture.