NewZed

Looks like fun. "Value" for who or what? Is it an investment for resale or are you driving it?

The two pronged sender on your 78 is a combined switch and sensor. Two devices in one. One prong is the switch for the relay and the other is the pressure sensor for the gauge. So you could use the sensor prong for the stick 78 gauge and leave the other disconnected. You don't need to buy a new sending unit. You might search the site and/or the internet for "ford inertia switch", it's a popular safety device around the modded car world. Although the Nissan design is better for mechanical malfunctions like if a fuel hose pops off and the engine stops running.

If you disconnect the oil pressure switch on a 78 the fuel pump will run whenever the key is on.

If the engine has been sitting it might be that the valve stems are gummed up or have surface rust. They stick, the cam lobe keeps going, and the rocker arm doesn't have any pressure on it to hold it in place. If it was mine I'd just keep the RPM down for a few hundred miles to let things wear back in. Although that's not what I did when I got my old had-been-sitting car. See if the wipe pattern looks the same after you reinstall them.

Check the simple stuff like the air intake. Make sure the throttle blade is opening completely. Check the intake system for mouse nests, they work fast. Make sure the filter is not clogged. Take the black cover off of the AFM and make sure the counterweight/vane is moving freely as you rev the engine. The AFM vanes have been known to bind. The only thing stopping an in-tune engine from revving and producing more power is air flow. Your symptom sounds kind of like an air flow problem.

I don't see spark plugs, distributor cap, rotor. Usually the first tune-up parts people think of. Here are some things to check that might offer a clue. Is the transmission shifting through the gears as you accelerate to 30 mph? What is the tachometer needle doing? Is it behaving normally, following engine RPM, or does it jump around? Do you think that the engine is running well, besides the lack of power? In other words, does it sound smooth or does it sound like it is missing or stumbling as you try to accelerate? Give more details on what, exactly, the engine itself is doing as you try to get to 30 mph and what happens when it stops accelerating as the speedo needle stops climbing. What is the transmission doing? Do you think it's functioning properly? Engine noise and tachometer needle are good indicators of engine performance. Exhaust smell is also a clue. There are two common problems with the old cars, the ignition module and the ECU. The ignition module will typically start shooting too many sparks when it goes bad and the tachometer needle will start acting weird. and the engine will run poorly. The ECU's tend to run very rich as they start to go bad, causing a very gassy smelling exhaust, then they die completely. To rossman's point, if your timing is retarded the engine will be way down on power. But if it started running poorly before you adjusted timing you'd have to wonder how the timing got retarded, unless something broke in the distributor. One way to check if your damper has slipped is to match the notch and groove on the timing chain sprocket and see if you're close to zero on the timing mark. There's a bunch that ran through my mind... If the engine is running well, it might just be your transmission. Try using the shift lever to stay in the lower gears and see if things are different. Separate engine issues from transmission issues.

#2 is low but it's within spec range, 10%. The engine should run fine just with maybe a lumpy idle due to the imbalance. You should definitely be able to go faster than 30 mph. The red on the camshaft is just factory paint, it has no meaning. Your rocker arm play is normal, the lobe was on the base circle (off the lobe), with no pressure on it. The others probably all do the same. Is it a manual or an automatic? When did you last give it a tuneup? Do you drive it often? Is it possible that there is water in the fuel tank, from sitting long periods between driving? Doesn't seem like a major engine problem. Probably some minor electronic or fuel problem.

You said you wanted it to rev higher. Where is your cam timing? Did you degree the cam to Schneider specs when you installed it? You can move the powerband higher by changing cam timing. Cam timing affects "breathing". https://help.summitracing.com/app/answers/detail/a_id/4706/~/advancing-%2F-retarding-a-camshaft#:~:text=A Basic Overview of Cam,the camshaft and the crankshaft.&text=Advancing or retarding the cam,other of the crankshaft centerline. https://www.jcmmachineandcoatings.com/understanding-combustion/degreeing-a-camshaft/#:~:text=Degreeing the Camshaft-,What is Meant by Degreeing the Camshaft%2C and Why is,that their rotation is synchronized. http://schneidercams.com/284-70F-14_LET6.aspx

Cam timing generally determines where the torque power curve is, high or low on the RPM range. Did you do all of this work yourself or have some help? There's some odd things in the overall story. No offense.

Gorilla has good stuff on their site and seems to make a good product. You can find them in the auto parts stores, on the shelf. Read this page and you'll see that hole size is not the issue. Yours have a specific seat style. Wheels either locate through the seat, or by the shank. Shanks require a precision hole. The others require a precision seat. https://www.gorilla-auto.com/gorilla-tech-tips

That assembly seems to be meant for permanence. It's not really meant to be unplugged. People that have had success have had to devise small picks and thin blades to get past the locking mechanism. In other words, you'll need to do your best Macgyver. Here's an old post about it, if this is the one you're talking about. Read this one and a couple more below it. https://www.classiczcars.com/forums/topic/60007-78-280-re-assembly/?do=findComment&comment=549453

I did a Google and found this. I'd wait and confirm. One's from Hybridz. Not looking good. https://zilvia.net/f/showthread.php?t=50158 https://www.google.com/search?rlz=1C1SQJL_enUS862US862&sxsrf=ALeKk012kyI3OARbRxjn53vqXgsMBXC7CQ%3A1605209360066&ei=EI2tX8fJA9ba-gTFpY7gCQ&q=S15+Helical+LSD+spline+shaft&oq=S15+Helical+LSD+spline+shaft&gs_lcp=CgZwc3ktYWIQAzIFCCEQoAEyBQghEKsCMgUIIRCrAjoECAAQRzoHCCMQrgIQJzoICCEQFhAdEB46BwghEAoQoAFQhT1Y4FFgoVNoAHACeACAAWyIAe4IkgEEMTEuMpgBAKABAaoBB2d3cy13aXrIAQbAAQE&sclient=psy-ab&ved=0ahUKEwjHkcnt3v3sAhVWrZ4KHcWSA5wQ4dUDCA0&uact=5

I think that the exhaust manifold with the turbo flange, and the J pipe to take the pressure to the manifold are the two items that are specific to the L28. The rest can probably be pieced together on the aftermarket. That's for EFI. Good stuff here: https://forums.hybridz.org/forum/90-l-series/ You can buy kits: https://www.cxracing.com/turbo-kit-nissan-datsun-240z-260z-280z-s30/turbo-kit-nissan-datsun-240z-260z-280z-s30-l28-l28E/TRB-KIT-IM-L28-280Z-NOIC Search words: https://www.google.com/search?q=datsun+turbo+kits&rlz=1C1SQJL_enUS862US862&oq=datsun+turbo+kits&aqs=chrome..69i57.4700j0j15&sourceid=chrome&ie=UTF-8 Carbs: https://www.google.com/search?rlz=1C1SQJL_enUS862US862&sxsrf=ALeKk01dUEG8FNHFMFvFit0jQT5xA-aymg%3A1605129681122&ei=0VWsX9XvBqrP0PEPw7iZqAU&q=datsun+turbo+kits+carb&oq=datsun+turbo+kits+carb&gs_lcp=CgZwc3ktYWIQAzIICCEQFhAdEB4yCAghEBYQHRAeMggIIRAWEB0QHjoECAAQRzoJCAAQyQMQFhAeOgYIABAWEB5QgKwPWN-1D2Ctug9oAHACeACAAWSIAdYDkgEDNC4xmAEAoAEBqgEHZ3dzLXdpesgBCMABAQ&sclient=psy-ab&ved=0ahUKEwiVnNiDtvvsAhWqJzQIHUNcBlUQ4dUDCA0&uact=5

77 and 78 have a very different style window and door. Might be that zcardepot just assumed they were all the same. What is that actually stops the window, at the bottom of its travel, on your car? That might be the clue.

Anything from 77 to 83 ZX will swap right in as far as 5 speed. If you get a mid-80 to 83 5 speed you'll probably want the 3.9 diff also. And a 76-78 propeller shaft. Your 75 should have the unique bolt pattern diff flange and propeller shaft. Any engine up to 1983 will swap in . I had good luck just buying a whole car that had been sitting for years. If you have the space you can save a lot of money that way.

This might be simpler and faster than a crank-mounted wheel. Several good articles on the web site also. https://www.diyautotune.com/product/54-mm-optical-trigger-wheel-for-nissan-l28et-or-vg30e/ https://www.diyautotune.com/support/tech/hardware/nissan-trigger-disc/ https://www.diyautotune.com/support/

People have taken those apart and cleaned them up with success. The contacts don't burn up they just get gummed up. Many people, myself included, have fixed them just by spraying large amounts of contact cleaner in to the assembly and working the mechanism. Not lying. Many people who buy a Z that has sat for years find that they don't have headlights or they only have high or low. It's probably just a light film of corrosion and a weak spring in the mechanism that can't push through it.

No, a real mod gave me that title because I get involved a lot. It's been a while. Not a mod. Can't move stuff. You'll probably find something. These old tachs are getting crusty, stuck needles is pretty common.

It should go back to zero. If it doesn't it's a mechanical problem, not electrical, probably just a gummed up mechanism. You don't want to mess with the adjustments, they haven't moved. Why post a tachometer problem in the V8 Tech board section?

Good stuff on the internet. Seems like generally the problem with these modifications is that the parts that they use to grip weren't designed to grip. They just create a way to jam the diff locked using parts that aren't supposed to be jammed. If the design was good the auto makers would use it. Fewer parts is cheaper and auto makers are all about making parts cheaper. https://grassrootsmotorsports.com/forum/grm/opinions-wanted-on-this-lsd-conversion/142829/page1/

Here's what they look like. If that helps. https://www.ebay.com/itm/3-PCS-FRONT-MOTOR-AUTO-TRANS-MOUNT-For-1972-Ford-PINTO-2-0L-3SPD-4SPD/152593939774?fits=Model%3APinto|Make%3AFord&epid=10003659700&hash=item23874ebd3e:g:0B0AAOSwFJBZScyo

Got a link to the video?

This is a bad reason to try to get to 9,000 RPM. Not logical. Buy a kit that is most optimal at 5,500 RPM.

Did you swap the pedestal also when you installed the 280Z distributor? The Z and ZX use a different pedestal and they're oriented differently. Take the adjustment screw completely out so that you can rotate the distributor as far as you need. See if that gets your timing right, then see if you can move your plug wires to get there. It might be that somebody adjusted the old distributor to work with an oil pump drive gear that was off a tooth. Now that you have stock distributors it's not "right" anymore. Set the timing mark on zero on the compression stroke and see if the half moon is in the right spot in the distributor hole. Here's some pictures, the first one is not quite right but shows the size difference more clearly. https://www.atlanticz.ca/zclub/techtips/distributor/index.html

Have you taken a good closeup look at the sealing surfaces? Use bright light and a magnifying glass. There's probably a clue there. You got single or double but they're both just a cone that sits on a cone. You can even put a final finish on the surfaces with abrasives. Look for cracks, imperfections, or crud on the sealing surfaces.