Zed Head

So you're worried about maybe using the wrong washer in the pump? The video looked good to me. The pressure is higher, stays up when the engine gets warm, and there's good flow to the cam shaft. I'd leave it and move on to the next issue. I think that every Z owner worries about their oil pressure. Although, and this might be for someone who's been deeper in to their lubrication system, I notice some bubbles coming from the cam shaft when you stopped cranking. I don't know where you could suck air in to the system except maybe at the gasket surface. Or the pickup tube in the oil pan. That would "suck" if it was there. Not sure how you'd diagnose that. You might try cranking again with the valve cover off and confirming that the bubbles are constant and not just residual air in the system. If you don't get bubbles, assume it's fine and just use it. It might not be worth worrying about though, just an observation.

https://www.atlanticz.ca/zclub/techtips/wiringdiagrams/75_280z_wiring.pdf

The wire colors and the plug shape are shown in the wiring diagram. The 76 color diagram might be a good starting point. Otherwise it's in the back of the 1975 FSM. https://www.classiczcars.com/files/category/1-wiring-diagrams/

I don't see that confirmed in the written description or the UK forum discussion, the words that are available from this CZCC thread. Beside that, the ownership history is still undefined. Overall, it's still a very thin story about a 260Z shell and some parts.

I'm going to guess that this is the "Fourways" mentioned in the other forum posts, linked below. I'd fill out the whole history, while it can be done. A single BSR crew member comment, from somebody's memory, just doesn't seem enough. Who is Fourways, and who has owned the shell since they bought it? Who installed the engine and all of the parts? Stuff like that. . https://fourways-engineering.co.uk/

Good luck to the OP, but I'm just trying understand how it can be worth $15,000 (~). Fun to talk about it. He needs the paperwork that supports the rumo(u)rs.

"cause Fourways probably installed them 30+ years ago. I read, then thought. And don't overlook the utility of the word "essentially".

I wonder if the doors are "shells" too. They don't seem to have any paint or hardware attached. The car might actually be worth more in parts. Quarters, fenders, floor pans, doors, struts/hubs, brake parts, fuel tank, etc., all essentially new. RB25DET, transmission. Is there a diff under there? Too bad there's no glass. Swirl pot/surge tank. Used to keep the fuel pump from going dry on the corners. Usually left hand turns on the Z's.

Bob Sharp has incredible powers...

There are four seals in the MC. Two to pressurize the front and back systems, one to keep them separated, and one to hold all of the fluid in the cylinder. Seems like your separator seal is not separating. Not sure of the actual dynamics but that seems reasonable, to me. Looking at the drawing it seems that fluid is pumping back and forth to various places with each pedal press. In your case it might be that the port to the front reservoir is clogged and fluid is getting forced past the separator seal (had to take a guess). Short would be - your MC is bad. Best guess. I found that some of the hydraulic parts I bought at the parts store had machining grit in the bores. Best to take them apart and clean them before installing.

The shift lever shows that it might actually have an engine bolted in place. I think that's a shift lever...

Edit - I didn't scroll down far enough to see the itemized list. It's a weird one. He says "The shell was bought with the intention to produce a fast road car " but doesn't say who bought it. Is that a conversion or just an engine sitting there? Like all of the other parts. I see a pile of parts. Interesting story. Seems like the asking price is more for the story. Not sure but I think I see the typical dirty fluid in the clutch and brake reservoirs. It has used tires on it, but missing one. It's a puzzle but there must be more clues there. Looks like a typical "complete tear down/restoration/dream", not finished. Excerpt - "As far as I am aware the shell has never been registered as a road going car either in the United States or the United Kingdom. There are thoughts that this shell may have been taken off the production line prior to assembly in order to supply the Bob Sharp Racing team for the American IMSA/SCCA championships or possibly to be used as a pace car - however there is no hard evidence available to support either of these theories. However, whatever the truth is in my opinion (and mine alone), judging from the condition it is unlikely that this shell was ever built into a complete or even an incomplete production car but others of course may disagree..."

It looks like the top of an air-cooled cylinder head. Aluminum, with fins, and a bunch of wires connected. Can't miss it. Or maybe this. They changed somewhere between 74 and 76.

50/50 antifreeze and water. Use one of those water injection systems the drag racers use. It really is tempting... https://www.summitracing.com/parts/hly-557-101?seid=srese1&gclid=CjwKCAjwh7H7BRBBEiwAPXjadu2x8WWIYmNEJcfSjgO7aXMBz-vIwfortTbyQiXSMhVZpvUwMmeDsBoCjpIQAvD_BwE

Usually. Actually it stands for Previous Owner. The ignition module is down by the fuse box in the cabin. Passenger side (right side). You might have to dig in to that ignition switch. Who knows what you'll find, considering what's in the engine bay.

See if it gets 12 volts when you turn the key to Start. The early 280Z's have yellow wires that go to the brake check warning lamp and other places. Do you see a voltage regulator? Might be that somebody wired in an internally regulated alternator. Looks like you're at the start of finally learning what a PO did to your wiring. Condolences for the pain that's in front of you now. If you have an MSD ignition it might be that your original electronic ignition module has been bypassed. And, maybe, the PO decided to wire in a relay for the coil also. It's looking like somebody just hacked in the wires needed to make it run.

Could you post a picture of that relay? A PO must have installed it for a reason. Might be that they were trying to fix the problem you're having now. Are you sure the car did not start life as an automatic?

Actually that bypasses ALL of the car's wiring. All you need for that are the battery cables.

The point about the links was not continuity through the links, but connection with the terminals. Continuity through the wires that are connected to the links. You check that by measuring voltage, not continuity. A 1975 280Z should not have a relay between the solenoid and the wire from the ignition switch. Unless the car started as an automatic. But, even if it does, the test would be to measure voltage at the relay activation wire when you turn the key to Start. No offense, but when you have a meter you don't need to do a bunch of cleaning. You just use the meter to tell you if the connections are good. Cleaning without using the meter doesn't tell you anything. You didn't use the words meter or measure once in your post. Not good. EFI is all about the meter.

Whenever I think of carbon buildup I get an image of the backside of the valves in my head. That's where you get a lot of flow disruption due to carbon buildup. Most of the stuff in the combustion chamber will blow out during an "Italian tuneup", I think. Search "carbon valve buildup" and there's a bunch out there. Here's one. The backs of the valves get a good washing in our port injection engines at high RPM open throttle. Gasoline is a good solvent. https://team.valvoline.com/diy/truth-behind-carbon-buildup On your oil burning - I found that when I had my old engine in the car that it would burn a lot of oil if I really went out and used the engine. I was testing synchros and transmission fluids and transmissions for a while and would burn a lot of oil as I raced on to the on-ramps and over the country roads. I also found that the engine ran better after a good beating, so I would give it a "tuneup" now and then just so that it would idle better around town. It was fun, a good reason to flog it. After I swapped engines, the new one didn't need that anymore and didn't burn more oil during a beating either. So if your new driving style is lower RPM highway stuff you might see better oil mileage.

Did you check all six cylinders? The booster port is offset to the back. I wonder if all six got the same wash. Picture from here - https://www.autopartone.com/products/79-80-datsun-280zx-oem-2-8l-intake-manifold

Read all of the things that have been recommended. There a bunch you didn't even acknowledge. Do those that you can do. Come back with results. You could hot wire the coil but without injector power it won't run. It's probably a dirty fusible link connection like SteveJ said. Common.

That's a good one. Other signs would be - does the brake light in the dash come on when the key is turned on, do the lights work, do the accessories like the radio and heater fan work. The screwdriver on the solenoid works because that's a direct to battery connection.