Zed Head

Stick a metal rod down there and see if that stuff is loose and breakable or tough and bonded to the surface. Give it a good scrape and see what happens. The tank sealer just needs a good solid clean surface to stick to.

Kind of looks like he might have been stiffening up the body for drag racing. How does the engine bay look? Are the factory L28 engine mounts in place? Looks like quite a project. Keep an eye out for a wrecked 280Z for interior parts. They're hard to find.

This is a weird thing, the welded hole. Even the automatic needs that. Some sort of hydraulically actuated thing? What's the back story on the car?

The typical wear parts really don't show much wear. Unless the original owner took really long trips.

Are these guys in on it? Love a good mystery. https://fiva.org/en/awards/fiva-awards/#:~:text=The FIVA preservation award recognises,under the patronage of UNESCO.

Seems like the guys writing the BAT words weren't sure about the 31,000 miles either. They say "shows" 31k, not has. Interesting though, the service records indicate not many miles at all from 1981, the 30,000 plus is all pre-storage. I pulled a few dates and mileages from the receipts. Too bad there's not more before 1979. 30,000 miles in 8 years is 3,750 / year. Weekend cruiser numbers. 15,000 / year is daily driver numbers and gets 120,000 total. So those 79 odometer numbers could be rollover numbers. Are the numbers all wonky, the rollover clue? July 28 1979 30,191 July 16 1981 30,395 July 17 2017 30625 August 1 2017 30626 Haven't seen an unrolled odometer so can't judge. Wear on other parts would be a sign also. Gears, throttle linkage, stuff like that.

You could just run a new piece of hose and get rid of the T (Y) entirely. Every plug is a potential leak. And if those braided hoses are original they're ready to blow. The coolant lines to the heater core are probably the most common cause of overheating. I think I just saw two stories about it on the forum, and I have my own story, coming up the Highway 26 hill at night, and not noticing that my temperature gauge was pegged out until I got to the top. Close enough to home to just keep going and hope. The heater core hose had split and was blowing steam by the time I got home. It survived but I was never really sure it hadn't made my head gasket coolant leak worse. Anyway, those old braided hoses are dangerous.

Actually, if you consider the thermostat as a "block" that kind of answers the whole question. Blocking it is just like having the thermostat closed. In that little cooling line only, not the main thermostat. Running a "bypass" is the common error when people get in to those types o lines, like for the heater core. Bypasses serve no purpose. I vote for blockage.

I'm just saying be aware of unintended consequences. The original line has a thermostat in it, which would be a restriction. If you just run a straight line you might create substantial flow that doesn't do much cooling. Think about the flow path of the coolant. It's supposed to travel past hot surfaces before going to the radiator. If it doesn't it's just wasted pump volume. You need a small amount of flow past the closed thermostat valve so that the wax pellet will see the hot water and open. Most thermostats have a small hole to do that. You're probably fine, and neater, just blocking the ports.

Your post reminded me of this book. It's what you really want. https://www.amazon.com/Restore-Datsun-Z-Car-Humble-2002-01-10/dp/B01FIWZ3PG

Enjoy the weird words, an ad somehow got incorporated and blended in to my quote of your words. Like The Fly. Something for you @Mike, not a big deal, just a little light. One thing you might do is to put a restriction in the line. The only purpose of that flow once you take the carbs out of the picture will be to heat the thermostat and it won't take much. And you might not even need that if your thermostat has the small bypass hole to accomplish the same purpose. Otherwise, like when bypassing the heater core, that flow does not cool the head like it should. It bypasses it, and in effect, reduces water pump volume. Just a thought. You need all the cooling you can get. Edit - I'm a slow writer.

Check the Downloads area. The Factory Service Manual should be there. From the top of the page...Resources>Downloads> https://www.classiczcars.com/files/

Some links I came across. http://datnissparts.com/4-5-synchro-hub-datsun-competition-nissan-motorsports-f5c71b-direct-drive-5-speed-also-is-3-4-hub-in-the-non-usa-fs5c71b-close-wide-ratio-5-speed-32605-e9500/ http://lescollinsracing.com/transmission/gearbox https://www.classiczcars.com/forums/topic/50549-fs5c71b-transmission/ http://www.nnzcc.com/wp-content/uploads/2016/06/240Z_-Factory-Transmissions-knowledge-overview-Options-and-Specs-JDMjunkies.chJDMjunkies.pdf Same post, different site https://www.jdmjunkies.ch/wordpress/2016-06-07/240z-transmissions-manuals-swap-possibillities/

The latch is usually adjusted for fit. Does it sit low compared to the body lines next to it? You might do better by pressing the hatch shut. I found that my car was sealed so well that it was air pressure inside that made the doors or hatch difficult to close. Try closing it with a window or door open and see if it's different. Dropping the hatch closed doesn't give enough time for the air to get out.

Fuel pumps do wear out eventually. But, when was the last time you changed the fuel filter? Noise from the pump usually means it's working harder, either pushing or pulling . You could have a clogged filter or junk in the tank. In the same vein, on the hesitation, when was the last tune-up? Pretty common to get so used to a good running engine that you overlook the periodic maintenance. I remember spending a lot of time looking for a big problem on a car when it just needed new plugs and points.

Pennzoil's brand seems to work just as well. Internet has it that Pennzoil developed the formula for GM (AC Delco). I wonder how Dutchzcar managed to find Slick50 in The Netherlands. Just remembered though that the other magic fluid for Porsche synchros is Swepco 201. Diluted with ATF for the Nissan units. But it came from Porsche world, a guy who owned a Porsche shop. JMortensen has posted about it. Maybe Swepco 201 can be found, it's more of an industrial fluid. https://www.swepcolube.com/products/swepco-201-multi-purpose-gear-lube

I remember Slick50. Based on how synchro gears work, that seems like a not-good choice for transmission fluid (no offense). It has PTFE particles in it to minimize friction. Synchros need a balance between friction and viscosity to allow the speed matching to occur. If you want to take a chance with $50 I'd try the AC Delco Friction-modified Synchromesh before tearing the transmission down. I'd just let the other stuff drain out and refill with Synchromesh. Otherwise, there's a post on Hybridz about modifying Porsche synchros to work in the steel synchro 5 speeds. I think that FS5C has steel instead of "brass" (yellow). https://slick50.info/manual-gearbox-treatment/ http://skepdic.com/slick50.html https://www.ftc.gov/news-events/press-releases/1996/07/quaker-state-ads-slick-50-are-false-and-misleading-ftc-charges https://forums.hybridz.org/topic/92246-to-people-with-experience-with-the-datsun-comp-5-speed-need-parts-for-one/

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The odds are in your favor. But there is a risk. You might hear a slight change in RPM. 6% less fuel. If you do, then just keep the plug jumped and go get tested again. You're so close before, it should pass.

Many of the jars that food comes in, like salad dressing and mayonnaise, have plastic lids that can be drilled and cut for use in the garage. I had one that I set up as a liquid trap for when I wanted to pull nasty liquid using a vacuum. Anyway, The shape of the device seems to lend itself to something like that. Here's a similar one, except it has a metal lid. Just run your electrical wires in the other port, seal it well, suck on the hose, and you're at high elevation. Don't let the cops see you though... https://www.amazon.com/Liquid-collector-vacuum-trouble-getting/dp/B077BRRL59

So you're saying that he should trust what the FSM says and go ahead and short that switch? Assume that a direct short is fine and won't harm anything. Here's the post with the image showing the switch-like behavior.

I think that I would unplug it first and see what happens. That would be open circuit, super-high resistance, just like an ECU without an altitude switch. Then connect a potentiometer, set to open circuit/high resistance and carefully dial in some parallel resistance and see if you get a change. A new puzzle. Yay.

I would wait on that. If there's a spring and an adjustment screw it might not actually be an on-off switch. It might be a potentiometer that varies resistance by atmospheric pressure. If it doesn't go to zero résistance you might short something out in the ECU. It had been in the back of my mind that it would be odd to have a switch that made a dramatic on-off change at a certain altitude. Your observations kind of made things more clear. It makes more sense that it would be a variable pot. So, you might be able to put a potentiometer in its place. If somebody wants to study the AFM pin-out and see how resistance on that circuit affects the signal to the ECU, feel free. Pin 9 is one of the legs of the AFM potentiometer. My brain is starting to hurt...

I'd just unplug it and jump the plug. Like Dave said. If it works there will be 6% less fuel so the air-fuel ratio will be leaner. Should be enough to get you past the test. It might even run better and you can just leave the 40 psi FPR on and drive it that way. The ECU will just think you're in the mountains. But, if it were me, I'd try to understand the switch better first. Just to be sure that it doesn't have some internal resistance. Remove the switch and find a way to actuate it if you can. It's just an option. My car didn't have one otherwise I'd know more about it.

California was ahead of everybody else on emissions. If the thing has a port or opening on it you should be able to just suck on it and fool the ECU in to thinking you're at high altitude. You should hear a change in engine idle if it's running. Easy test.