Zed Head

The fact that you can kill the engine with the idle adjustment screw is a sign that any vacuum leaks are small. You're cutting off the air supply. If there was a vacuum leak it would most likely keep running. The blown FPR diaphragm is an easy one to check. Pull that vacuum hose and check for fuel. Run the fuel pump while it's off, if it's blown fuel will drip from the FPR.

The temperature gauge sender and the temperature sensor are two different things. What year is your Z? Does it have the original ignition module? Original distributor? What did the tachometer needle do when it was running poorly? That's a sign of module problems, if it jumps around. Ignition module or ECU seem likely, especially if they are original parts. They're old. But the distributor's pickup coil and the EFI and/or fuel pump relay are also possible. My car had problems with three of those four, and I have found bad pickup coils on parts cars. So, in total, I've seen all four (five) go bad.

I thought the same thing when I read that. Sometimes it's nice to let the car do the work. Too bad the autos don't have a bench seat. No offense. A bench seat has its advantages...

You should get some pictures from underneath. The rust spots. Looks like a nice car.

Looks like you're on the right path. Good luck.

For marking or confirming the damper pulley I Ike the method of marking a certain distance down on both sides of ~TDC then splitting the difference to mark zero. The crankshaft can move a few degrees at TDC with almost zero indicator movement because the rod end is moving almost sideways. Don't you trust your damper pulley marks? You don't need to be super accurate for installing the head or timing chain.

Wet plugs is too much fuel not clogged fuel supply. The A/F ratio screw is for small adjustments. Wet plugs are a gross A/F ratio problem. Wrong injectors or bad readings from the coolant temp sensor, or maladjustment of the AFM.

OMG. Does the guy that bid $55,000 know? Crazy numbers...

I don't want to give you a hard time. But you are pretty far off on the basics of how an engine works. You seem to have the right tools, you're just not using them correctly. Use your timing light and point it at the marks on the damper pulley with it connected to plug wire #1. That is how you set ignition timing. The oil pump and the distributor tang position don't tel you what the timing is. You have to measure it with the light. Get on to youtube and watch a few videos on how to set ignition timing. It will help.

What is the ignition timing set to? Have you confirmed spark? Should have added to part #1. Cant; remember what you've done. Like starting over.

@firediamond In case he doesn't check his threads...

While you're waiting for the green one this one looks interesting... https://bringatrailer.com/listing/1971-datsun-240z-126/

They're being "marketed" for the 300ZXT's. The fit problems with their use in the Z's is well-known. All kinds of tricks tried, cage-flipping, adjustable control arms, cutting and rewelding, etc. The main reason that people want them is for their increased strength. If you don't have over 200 HP, 250 ft-lbs torque, and big grippy tires, they don't offer much over the plain old u-joint half-shafts.

Post an ad in the Classifieds area, with more pictures and data, and a low price. https://www.classiczcars.com/classifieds/

Microsoft wants my money to view your video. Not ga do it....

It just shows the striking lever/rod being moved around in the rear case. Here's another link. https://imgur.com/a/KuNJPz0

That one picture looks nice. I don't think it's going to be enough for $20,000 though. Do you have more? Do you know the mileage? It's not listed. Also, head gaskets aren't rebuilt so that part doesn't make sense. Good luck. Supply lots more info and you'll get more responses.

@zKars apparently has a big collection of parts.

@Dave WM and @EuroDat and others have rebuilt their transmissions. Might have some ideas. Here's a good site for browsing parts. Better exploded diagrams than the FSM. http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train

It's odd that it gets stuck in reverse. Sounds the shifting rod is binding. There's no bushing that needs "pushing" in with tools. There are are two plastic bushings, one on the end of the shifter and one (two piece) bushing at the shifter's pivot point. Take a picture of your shifter and the bushings, we'll see how worn they are.

Did you try it with the front case off? Just the forks and shifting rods? Separate the potential causes.

A used one would be fine. Any idea on how the plate broke? @borini63 sells parts, he might have something. Shipping should be cheap.

from where?

Here are some flanges. Not sure he has stock though, he makes them in batches. http://www.chequeredflagracing.net/Datsun.html

Oops. not the right part. You need the flange, not the axle. The u-joint axles are plenty strong.