Zed Head

Still can't tell if the rotor electrode is pointing at the terminal your finger is on. It might also be that you need to turn the distributor. Get the cap in your hands and see if you think that the spark will jump to the #1 terminal when the timing mark is at 10 degrees. Or have a friend turn the distributor back and forth slowly while you crank the engine.

(Edited to avoid exploding heads...) But, using the normal procedure is best, because then everyone else will understand it. w3wilkes post is the one you want, but you need to set your timing mark at zero on the damper pulley and confirm that you're on the compression stroke, then make sure that the rotor under the cap is pointing at the #1 terminal. Making sure the rotor is pointed at #1 is very important. It tells you if the oil pump shaft and distributor is installed correctly, like Mike described.

Show the distributor cap with #1 plug terminal identified, and confirm that the firing order is correct.

You need to show the wires to the distributor to know if the firing order you used is wrong or not.

About 5:30.

Looks like I'm about to get some makeup meme...

Couldn't really tell from that diagram which is positive and which is negative. Why would negative or positive matter if it's just sensing power? (Edit - actually I don't really understand how that device works. Maybe it's "sensing" sparks? Current flow? Whatever it is, the positive side might work the same. @SteveJ @Captain Obvious ) If you have another load on the negative terminal of the coil that could screw up your tach signal. I'd disconnect that before you get too far along and see if it starts working. I don't know if the condenser will help you with that scheme. If it fixes the tach problem try using the positive side of the coil for the power signal. Edit - actually don't try this. It might be a direct short, depending on how the device works.

Is it an inertia switch? It looks like it supplies power to the coil also. Have you disconnected/unplugged the factory ignition module? While you're down there you can also test continuity back to the coil negative. It's a branched circuit, one to the ignition module, one to the tachometer, one to the ECU. The condenser/capacitor on the blue wire is easy to setup. That's what worked on mine, with a GM HEI module. Any condenser from an alternator will work. The wire to the capacitor goes the coil negative, the capacitor can be mounted on the ground point on the manifold, nearby. It's a cheap quick test if you have one laying around. Won't hurt anything.

By "tach sense" wire you mean the blue wire that heads back past the ignition module, right? What is this "fuel safety relay", and how is it connected/wired? That would be new to the system. The tachometer seems sensitive to the signal on that wire. You could disconnect it for a test and see what happens.

AFM.

Here's the guts.

It was just him and I and I had to leave. He was alone...

Did your family do all of the service or did you take it to a shop or dealership for service? Does anyone in your family own a Subaru?

Pickup trucks used the 4.11. 240Z's did not come with a 4.11. Nissan might have went with the recessed plug for looks. They even built a special shield just to cover a bolt head in the back on later cars. On a truck an ugly square head is not such a big deal. But, Whitehead is just using the same R180 picture for all of his R180 listings. So, who knows what's what there. https://whiteheadperformance.com/product/nissan-oem-3-54-r180-diff-differential-used-datsun-240z-260z-280z-280zx-510/ https://whiteheadperformance.com/product/nissan-oem-3-70-r180-diff-differential-used-datsun-240z-260z-280z-280zx-510/ https://whiteheadperformance.com/product/nissan-oem-3-90-r180-diff-differential-used-datsun-240z-260z-280z-280zx/ https://whiteheadperformance.com/product/nissan-oem-4-11-r180-diff-differential-used-datsun-240z-260z-280z-280zx/ 78 280Z with bolt head shield. Whithead's label implies it's just a stock photo he picked up somewhere.

What procedure are you using to adjust rocker arm clearance (lash)? If it ran fine before then your work must have done something to change something. Are you rotating the engine and camshaft as you measure and set lash to be sure that each lobe is on the base circle? Seems like a very loose rocker arm is the most likely possibility for that kind of noise and the work you did, considering that it "ran fine" before. Don't really see any other moving parts in the engine that you touched that could cause it.

That noise still sounds pretty solid. Like objects with large mass. I'm changing my guess to rod bearing. Or not. Can't really tell. Your videos are at idle. What happens if you rev the engine?

Search "280Z tachometer" and you'll find pictures of the plug out of its socket. Might give you the confidence to pull harder. My tachometer used to stick when the weather got warm. The capacitive discharge ignition systems are well-known for causing tachometer problems. MSD, Crane, etc. Might be worth your while to reconnect the old ignition module and see if the problem goes away.

Here's your historian. @Carl Beck

Somebody stuck a fill plug in the drain hole, probably because the socket type drain plug is a pain to remove. Browse through these listings, below, and you'll find a few pictures of the original setup. I don't think that Nissan did any "one-off" plug arrangements. You should post the replacements that are not of this type just so that people can see them. Might be an aftermarket guy offering an improvement. https://bringatrailer.com/datsun/240z/?q=240z

One of the great ironies of the situation, and one of the reasons that I believe in the vaccines, is that any pharma company that released a vaccine that damaged people would get destroyed in the stock market. The spotlight is so bright that they would not be able to BS their way out of it.

The point was that FDA approval is not worth much. I think that overall we got got lucky that there are good individuals in these various bureaucracies that know how to work within them to get good things done. But eventually the bureaucracies will get so corrupted that nobody can get anything done. It's already happening in branches of government. Let's hope that some rebuilding happens after this close call. And be thankful for the people that pushed the working vaccines through. If you believe the reporting, they actually work, with no side effects. I feel fine.

The Black Box. Probably would have had to get a "Q" clearance. Q used to mean just a certain level of security clearance. I assume that "Q", whoever Q is/are, has/had a Q clearance, hence the moniker "Q". Anyway, you missed out on the whole Boeing culture in the PNW. Work hard, get laid off, collect unemployment knowing that the cycle will repeat. I had some friends in the Boeing world. No offense Racer I don't know if you're an engineer or not. But there really is a "Boeing way of life" out here.

The FDA is not really what people think it is. It suffers from serious "mission drift". It needs a major overhaul. https://www.reuters.com/article/us-health-coronavirus-vaccines-fda-exclu/exclusive-top-adviser-steps-aside-from-fda-covid-19-vaccine-reviews-over-potential-conflict-idUSKCN26E3IW https://ethics.harvard.edu/blog/risky-drugs-why-fda-cannot-be-trusted

Some work with a meter and a battery, should do the job. Measure resistance and direction. A fun project.