Zed Head

Yikes! https://bringatrailer.com/listing/1977-datsun-280z-109/

Rotating the distributor body will not affect the points gap. I talked about when the points should be open in Post #11. The points open and close each time the distributor cam lobes go by as described in the video I posted. They open and close about 15,000 times per minute at 5,000 RPM. Rotating the distributor body changes the time that the points open for each cylinder, in relation to the piston position as it moves up and down in the cylinder. Rotating the distributor body is called "setting the timing". The shaft with the lobes stays attached to the camshaft but the points move in relation to the distributor cam lobes because they are attached to the distributor body. Rotate the distributor body as you watch the points and lobes.

Another.

This video might help. I copied from the "point" where he talks about the rotating shaft. Watch this video and others from the sidebar.

The stuff in Post #11 will answer the question about the oil pump. If you do the things and the rotor is pointing the wrong way then you'll know the oil pump is off. Still might not need to change anything. Just get the timing mark and the points opening and the rotor alligned with #1, then put the rest of the wires in. But #11 answers many questions. Do #11 (make sure the cam lobes are up), take pictures, come back. Worst case is the lock down screw won't have a hole to thread in to. Then it can be decided whether or not to reset the oil pump. Progress is slow but it is happening.

I wrote a bunch of stuff but will just say instead that idle and pressure tests in the driveway might not be replicating the loss conditions of driving. Loads and temperatures are different.

For where you're at right now I would do the above. Whenever you try to start the engine and nothing happens you suck raw fuel in to the cylinders. Do the above, pull a spark plug and make sure it's not soaked with gasoline, then try to start it with starting fluid if the plugs are dry. When you spray the fluid in to the carburetors make sure the carbs are open so that the starting fluid can get in to the intake manifolds and cylinders. Also consider the choke.

To put the second part above in to useful terms - Rotate the engine until the timing mark is at 10 degrees on the damper pulley, on the compression stroke. Then loosen the distributor clamp and rotate the distributor until the points are just about to open. Make sure that the rotor is pointing at the #1 position of the distributor cap. Clamp it down and try to start.

Yes. It's common to rotate the distributor while trying to start an engine with new parts, to get the ignition timing close enough to start. Unfortunately it's usually done by people with experience who understand ignition timing. Another thing that's often done is to watch the points as you slowly rotate the engine by hand to see where the timing mark on the damper pulley is when the points open. Spark happens when the points open. Rotate the distributor so that the points open at about 10 degress advance, and make sure that the rotor is pointing at the #1 cylinder electrode. This will get the igntion timing close enough to where the engine should start and run. Then you can set the timing correctly using a timing light after the engine is running. Spark plug wire order is 1-5-3-6-2-4, in counterclockwise rotation.

The original high miles engine in my car used to leak coolant from the right rear area of the head/block interface. It only leaked when cold and sealed up after the engine warmed up. Took me a while to figure out since there was no steam or odor from hot coolant boiling away. I noticed some staining from where it flowed after escaping. It was a bad headgasket but the bad part was only a coolant sealing area. The port to the heater core is back there also.

Where are you spraying the spray and what is it? Is it real starting fluid? Have you measured cylinder pressures? Compression. Have you pulled a spark plug and examined it? Maybe you flooded it.

You said old rebuild in your first post. Were you expecting better? Sounds like an old used 280Z engine. These engines will continue to run well even as they burn lots of oil. What are you trying to determine? I'd pull the valve cover and check the timing chain for wear (notch and groove), the oil spray bar for damage (if it has one), and the rocker arms and cam lobes for wear. While you're there check and adjust valve lash.

There were only two compression ratios for the NA L28's. 8.3 and 8.8. A stock N42 block should have either an N42 or N47 head. That would give the 8.3 CR. Your pressure numbers seem low but the adapters or length of the hose to the gauge can affect the ratio. More adapter or hose looks like more combustion chamber volume. What do you mean by "air flow meter at the intake"? Are you doing your measurements with the intake manifold removed?

Curious - are you getting new rocker arms? Word is if they have any wear you should get them resurfaced. The old wear won't match the new cam. New cam needs new wear pad. Again, just regurgitating...

Funny, looking at an actual rocker arm it seems almost reasonable to just use the base circle change directly. Because the contact pad is almost over the valve stem. And there is some room on each end of the wear pattern for error. Seems like you could take your 1.55 mm number and just fudge it based on the existing wear pattern, adding a little bit for the relatively small distance the lash pad is extended from the rubbing pad. OR you could just stick a 1.55 mm shim under the 300f base circle and take a measurement at the lash pad. Since it's getting bigger. Replicate the L490. One question for you would be whether or not the valve tips on your current setup have been ground in the past after a valve job. Apparently the good machinists do that so that all of the lash pads are the same size. From what I've read here on the old forum. So Diseazd's recommendations might not work well since it's probably based on standard valve sizes. Not an expert, I just like to talk about things.

You'll be walking in circles if you let your leg get pulled like that.

Actually, with today's CAD programs you could probably just draw out the picture above, make the changes and let the computer do the work. I think that there are even free simple online programs out there. Gotta sell those 3D printers. Sometimes I do long division with paper and pen just to reawaken that old shriveled part of my brain. I wonder if it's even taught in school anymore.

The title question is basically about your own abilities. Only you know the answer. I would draw it out as a trigonometry problem. I'm not saying that I would get the right answer just that that seems like the starting point. Two triangles.

See other thread...

Retap the fitting for NPT. ...

I mentioned that earlier but it got no response. He might find an NPT that is close. People do for the oil pressure sender port. He could even put the fitting back in and use a hose and bolt. Or thread the inside of the tube and use an NPT plug, it looks pretty thick. Or take the fitting in and get a compression fitting. He'd have to cut the flare off of the end. That's what I emant earlier about "mechanicing". Just pick a path and make it work. Could also focus on getting the engine to run with no cooling. If it's a lost cause there's no point in worrying about the cooling system. Many ways to move forward.

Take the fitting that you removed to Ace Hardware and ask somebody to match the threads with a brass plug. I can't tell if it's straight thread or tapered but the right person at Ace should know. Get some thread sealant too. https://www.acehardware.com/search?query=brass pipe plugs https://www.acehardware.com/search?query=pipe thread sealant

I've had a few apart for small things but have not replaced the adapter plate bearings. From what I've read the hardest part is getting the gears or bearings off of the long tail shaft. But people have made their own tools from pipes and other odd things. I think it's this illustration. You can always tear in to it until you get stuck then put it back together.

I'd use this one. Should be a Manual Transmission chapter inside. A sample. There's even a specific bearings section.