Zed Head

Watch the tachometer needle. See if it starts acting weird before it dies.

That would be the water inlet. The heater hose goes to it. The outlet is at the block, inside the cover.

If the old seal rubber wore through to the wire spring there might be a groove in the slip yoke. Not uncommon.

The statement in the book about the bolts doesn't make sense. Maybe he had a bad experiencing in the past and assumed it was the bolts. Like any bolt and nut it just uses leverage to apply force to the cap. Break it down to simple physics and you can't find a reason that mixing them up would matter. I'd be more concerned with metal fatigue and stretching, from the first usage. New bolts and nuts is probably just a good safeguard against failure.

I ran a long wood screw through the middle and let it press off of the inside of the passage. It cocked a bit so I punched one half in and pulled the other half out. Rotated on the edges. Then I grabbed it and pulled it out. If you get the middle torn out the edges will fold in pretty easily with a punch. The sealing surface is wide and you can use sealant on it.

Core. https://en.wikipedia.org/wiki/Core_plug

No, the FPR controls fuel pressure. It is a spring-loaded valve that only opens when set pressure is reached, when the spring force is overcome. A weak fuel pump could result in low fuel pressure but that would not cause the problem that you are having. You might as well get the fuel pressure correct though while you try to figure out why the injectors are getting a signal to stay open like you're at full throttle. It might just be your throttle valve switch. But if it is it will show up when you do the tests in the FSM or the Guidebook. The TVS and the coolant temperature sensor can affect fuel, as can the AFM. And the CSV. You just have to sit down with your meter and start testing. You'll be done much quicker than you think and something will probably show up.

A good way to learn is to measure things that you already know are correct. Battery voltage, an injector resistance, resistance across a good ground. Look at correct measurements then the incorrect ones will make sense. The last time I measured amperage I didn't need to because voltage showed me the same result, a circuit that was actuating a relay. Then I blew the $12 fuse in the meter when I forgot to change the leads back and checked my battery voltage. You'll never really need to measure amps on a Z or ZX. Get the leads on the voltage/resistance terminals and never move them.

I like your oil ring theory. I think that worn valve seals show up as smoke on a restart because the oil leaks down while the engine is off. Oil scraper problems don't show up on a cylinder pressure test either.

Actually the early 5 speeds are the one with the gap between 2nd and 3rd. The later "close ratio" boxes are well spaced. I've used a 3.54 behind a close ratio with the tall first gear. It just takes more attention to the clutch. If you live on flat land it won't be a big deal. If you live around some hills you'll put extra work in to your starts from a stop sometimes. Don't overlook tire size in your calculations. And, like Dave said, you might find that 5th never gets used. Why do you think 5th is "short". Does the engine get buzzy? I found that once I got my engine squared away, cruising at high RPM was much nicer. An unbalanced engine is annoying.

Don't forget that you'll need to have the 71B case machined to fit the 71C oarts, in order to use a 71C on an L6 engine. Also, the 71C 3rd gear is probably the same as your 71B third gear if it's an early 71C So, really, the fastest way to get back on the road is to just swap in a used 3rd gear. There is little strength benefit to the 71C unless it is a late 90's 71C with the wider gears.

Seems like you still have a problem. You tried a new gauge and still got low pressure. But the engine is running rich with 190cc injectors. Something is causing the injectors to stay open too long, Could be the AFM, the ECU, one of the temperature sensors, who knows. At least you know which parts are good though, so you can focus on the the other possibilities.

People use "short" and "tall" differently and many use them incorrectly. Not sure what you mean by short. A 3.54 will give you the "tallest" 5th you can get with any transmission, unless you find a 3.36 diff. If you install a 3.9 5th will get shorter. I'm using tall and short as I understand them Tall is lower RPM, short is higher RPM, or faster acceleration. With short you run out of RPM sooner. There are only three 5th gear ratios available. 80-81 is in between the other two. After 81 gives you the lowest cruising RPM. "Tallest" 5th.

There are fairly simple things that people do for minor improvements. Paint the inside of the block with glyptal to seal it and any casting sand that might still be there, and for quicker oil drainback (after you have it hot-tanked). Clean up the coolant passages of casting flash with a grinder (before you have it hot-tanked). Apparently there can be quite a bit. Smooth the crankshaft weights so they don't hang on to oil. Balance things, generally. The "How to Modify" book is worth a look for ideas. Since you have time.

21 and 26 here show a difference. Nissan calls both "flywheel"s and considers them part of the crankshaft. http://www.carpartsmanual.com/datsun/Z-1969-1978/engine-280z/piston-crankshaft

All I hear is an engine that seems to be at high RPM, but I'm on a computer with bad speakers. A "chime" is like the noise a wind chime makes when the wind blows. Dainty. Didn't hear that. What is the idle speed RPM?

Your engine is looking more and more like just a high miles engine. That glued on badge is an odd thing now. Aftermarket sprockets only have to match the tooth pattern and shape. They're not rebuilt like alternators, they are brand-new parts, but made from the aftermarket manufacturers' tooling. Look for a good brand name. Cloyes seems to be well known in timing sprockets and chains. Often you'll find the same exact part for different prices from different suppliers. Sometimes there's only one company making a part so you might as well just buy the cheapest, unless there's a warranty.

Are you using copper tube from the pump to the carbs? That's interesting. The tube looks of small diameter. Is it a new thing or has it been running fine like that? There's not much to gauge placement. The fitting needs to be between the pump and the carbs. Describe a gremlin and you'll get more ideas.

My 81 engine had steel gusset brackets. I've read that they were for NVH reduction. If you look at the engine-transmission assembly from the side you can see that there's some leverage there. There's a lot of weight hanging under the last bolts in the engine, without those brackets.

Aluminum usually cracks as it bends. You probably have the mounting surface machined to run true to the tire surface by a good machine shop. Probably expensive to do though.

I had a warranty just like that so I hooked up my spare EFI system to make sure it ran right. You'll be well past 30 days by the time it runs so really you don't have a warranty. Probably fine, they're tough engines. I was just trying to get a feel for how detailed your plan is. You could run a carb and go crazy and have more flexibility.

Just to fill out the possibilities - you don't have to remove the head to replace the timing chain and sprocket. On the other hand, the chain and sprocket might have been replaced when the head was rebuilt, so the head might have that amount of wear. And, to speedroo's point, a counterpoint - don't assume that you can do the best job possible. Really, just do the cost/benefit analysis and be aware of the rabbit holes...

The notch and groove are a better measurement of chain wear than the finger test. Even looking at how far the tensioner is extended will tell you more I think. As far as performance improvements you probably want to consider your engine management system. The stock EFI system is designed to work with a specific engine. These aren't like the old carb'ed engines where you just bump up the compression, put a cam in it and some headers and you're done. You might get more power with some bolt-on mods but it will run like crap for daily driving. I like a full plan myself, but doing things on the fly is still fun.

It's already broken in. I'd just fill it with the oil you intend to use and go right to whatever oil change schedule you normally follow. The only new wear surfaces are the valve ends and the lash pads and they don't see the same sliding wear that the cam lobes do. One opinion..

They're all good. Although I was actually hoping for clouds the other day. too much UV for me. To Av, it's easier to evaluate somethings when the engine is assembled. If you want to keep the unworn parts. If you're just replacing all of the wear parts then it doesn't matter as much. You can drill two holes in a piece of flat steel bar and bolt it to the crankshaft to lock it down, for removing the various bolts.