Zed Head

carpartsmanual says the 4 speed forks will work, if you get the right 4 speed. It also says that you might get the wrong 5 speed parts, and be in the same pickle. I'm repeating myself, but just in case you didn't look at the link. It's not the number of gears, it's the part number.

Redline and Pennzoil Synchromesh are both good for the old Nissan transmissions. Not much better that I've seen written about or tried. There's a lot of buzz about the "Friction-Modified Synchromesh", but if you already have the regular stuff, not really worth spending extra. Use the Synchromesh, I'd say.

What is being flushed? The moving parts are self-cleaning and the non-moving parts aren't affected by "stuff" on them.

I'm not much on electrical but isn't the power of the magnet, the coil, determined by current? Which, of course, is related to voltage. Just pointing out that if you have a relay that's not actuating, and you're reading lower than expected voltage, getting a different relay might not be the "ideal" solution.

You might have a brake fluid leak.

I found an article that shows how MSD's ads are deceptive. They describe set-point timing retarding as "curves". They're not curves. They're just rebranding their rev-limiter technology. Pretty sad, MSD used to be top of the game. https://bangshift.com/general-news/tech-stories/engine-tech-how-a-programmable-ignition-can-make-anyone-look-like-a-pro/

The bushings need to be tight also. If they're destroyed you lose a lot of travel.

Apparently there are three 4 speed shifters also. I used my 1976 4 speed shifter on a 78, 81, and 83 5 speed and never had any problems. http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-control/4-speed/from-sep-71/27

Looks there are two different 4 speeds, and two different 5 speeds. Parts 5 and 6 respectively. There's overlap. Looks like you got mismatched years, maybe. http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-control/4-speed/from-sep-71 http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-control/5-speed

I posted in this thread about using an MSD or Crane module but I don't think that their programmability is very complex. Their ad copy is deceptive. Here is a system that does what I was thinking of. Lots of ways to get spark control, especially in today's programmed world. Somebody has probably developed an app that will let you use a "phone" to run your engine. https://www.cbperformance.com/CB-s-Black-Box-Programmable-Timing-Control-Module-p/2013.htm

The tiniest scratch in the bore will leak. My car had a faint scratch from the wire spring that holds the dust seal in place. The PO must have let it slip and it scratched the bore. It worked fine but let a few drops of fluid leak after each drive. Took me a while to figure out why my tire had fresh liquid on it on a dry day. The PO also put the calipers on the wrong sides. He put the work in but just missed on the results.

You left out 280Z distributor + external ignition module. GM HEI, MSD, Crane, and other modules. Some of them are programmable. The 280Z distributor has the variable reluctor trigger, which is very solid and dependable.

Looks like a Nissan reman. Rebuilt to Nissan specs. Should get 200,000 + miles from it. Do you know where it's been stored, and how? Does it have oil in it or is it empty? I would assume that Nissan coats the internals for rust prevention in preparation for shipping and storage, but who knows how long that lasts. Might be worthwhile to inspect rust prone surfaces before starting it. I don't know when Nissan stopped supplying reman engines but I'll bet it was over 20 years ago, at least. That engine has been floating around for that long. Fixed your picture -

Most electric pumps come with a piece of rubber to wrap around the pump and isolate it from the body. How is yours mounted?

Should be very easy. How about some pictures of the reman engine? We love to see other people's cool stuff. Is it in a box? Who reman'ed it? Nissan or someone else? Here are some images I stole from eBay. The ZX manifold is "shorter" and has a different angle to the flange. After 80 or 81, I think, they also had O2 sensors. https://www.ebay.com/i/383271658929?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=383271658929&targetid=541454198852&device=c&mktype=pla&googleloc=9033356&poi=&campaignid=6470549460&mkgroupid=81274343007&rlsatarget=pla-541454198852&abcId=1139336&merchantid=113625313&gclid=CjwKCAiAlO7uBRANEiwA_vXQ-1Ut8e94uWjLqn051V6ppSf1lEVw4fN47-rL18plbyR1TgFpPfq1RhoC-6gQAvD_BwE https://www.ebay.com/i/113846585162?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=113846585162&targetid=596465995348&device=c&mktype=pla&googleloc=9033356&poi=&campaignid=6470719577&mkgroupid=81597521270&rlsatarget=pla-596465995348&abcId=1140476&merchantid=113625313&gclid=CjwKCAiAlO7uBRANEiwA_vXQ-8FYIoFu21zAR6UlYdW4Q46ciHF9HVExnLM_lsVSp0AMijOc2agcsRoCBycQAvD_BwE

The damper and pulleys should swap easily. No need to do so though. Since you're using carbs you don't need EFI hose. Just get some quality fuel line. You will probably need to do some exhaust system work, depending on where the L28 came from and how complete it is. The L24 manifold and down pipes might be smaller than L28 parts. 280ZX manifolds are different from 280Z manifolds. Basically though, the L28 and L24 engines are almost identical on the outside. Everything should swap over.

Here's another way that your timing could have retarded - you set the timing with the vacuum advance actuated, and the hose has fallen off. How did you set the initial timing and is the vacuum advance hose connected to the proper port on the TB?

What's wrong? Not really clear what the problem is.

Sounds like something might have come loose in your distributor. You said "good", maybe there's a number associated? You measured a zero later. If timing went from good to zero then something has changed. Retarded timing will make the engine run like crap.

They used to be available from Courtesy. Only one thickness though. You can stack the "ones" and get whatever thickness you need. http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-gears/5-speed/12 https://www.nissanpartsdeal.com/parts/nissan-shim-brg-0-1~32218-e9000.html

Swap tap for pound...

What is your new goal? Generally, for anyone with a 280Z, running through the electrical checks in the 1980 EFI Guide is recommended, along with verifying fuel pressure, and giving the engine a solid tuneup. Valve lash, timing, etc. Problems with the 280Z engines are usually a collection of small things, rarely just one big thing. Each correction of a small error closer to specification will make the engine run better.

Can't remember for sure but I think that I found an edge on the adapter plate and used an aluminum rod to break it free from the front case. As you're finding there's not much to bang on otherwise. Somebody might have used a strong sealant on yours.

superlen makes a good point. The real issue might be that the engine is not getting to operating temperature. Or, maybe, the coolant level is low so the sensors are not reading actual engine temperature. Or, both sensors are fine but you have a flow issue in the thermostat housing. Anyway, temperature and the way the engine runs are your concerns. Plugs much darker than those have run fine in many of these engines. Check your cooling system closely, make sure coolant is flowing and the thermostat is actually closing, and that it's actually there. Many people have found that a PO removed their thermostat, trying to cure an overheating problem. The thermostat is actually a "heating" device, stopping coolant flow until the engine is warmed up.

With the unibodies sometimes the pieces you think are important aren't so much. Don't think that you need big solid frame rails for the car to be solid. The car is a steel box, with a few reinforcing pieces attached strategically. Many members here have cut away large sections of their cars to repair the rust.