Zed Head

It looks like this, below, but if it's intact it will just be a squarish lump in the wiring harness. If the harness is broken open and you only see the wired piece, with the bullet connector bare, you'll know.

Might be for assembly in the factory or servicing. A lifting bracket might install there.

It's a "knockoff", not actually made by Standard Motor Products. The eBay ad is a lie. The one on Rockauto shows a true manufacturer, Ultrapower. The eBay ad says SMP, but is false. Notice how they avoid defining "manufacturer" and instead use part number or brand. It's a con and eBay is enabling it.

I edited Post #19. It's the front case that causes the rods to move.

It's a performance modification, adding an extra head bolt. The PO is actually an expert in Z engines.

This is not the same as after it's together.

Lots of good ideas here but they all say the transmission will probably need to be removed to find out. It's still not even clear that the gear shift lever moves. The OP hasn't described moving the lever. It might not even have a lever. Trans rebuilt, installed, key turned to Start car jumps, clutch pushed in car doesn't. That's all we really have. The only conclusion is "transmission stuck".

That looks like the right part but I think it's a scam like "New" alternators. It should be flagged as deceitful on eBay. Look at the words and compare it the real part on Rock Auto. https://www.rockauto.com/en/partsearch/?partnum=LX516

Using a block of wood is a good idea. I've messed around with removing and replacing those pins and they are difficult. You can build a little holding jig, two blocks of wood next to each other, to sit the piece in the groove between, to keep it from rolling. Filing the end of the pin down to a sharper point to give it a better start helps also. The end of the pin doesn't matter once it's installed.

Yes, you can get both shift rods locking up a gear, two separate gears, before installing the case. That's actually very likely, looking back through the posts. But I think that the gear shift lever would be locked up, since it has to move the rods. But, if the shifter bushings are bad it might not feel like it. Mr. Ape threw me with his comment about the shady mechanic. Didn't realize it was him. What happens, what Patcon is suggesting, is that when you're installing the rear case both shift rods get moved at the same time, resulting in the trans engaging two gears at the same time. You could probably figure which ones by looking at the diagram. What people do to avoid that is to put the trans in to one gear before installing the rear case. Sounding like you installed the rear case with the trans in neutral and have that problem. It's a fairly common problem, apparently, I've done it myself even after reading about it, but noticed it before I torqued everything. And....you still have to remove the transmission to fix it. Edit realized that it's actually the front case that is put on last. AKA "bellhousing". That's when the shift rods get pushed backward. I first saw it described in the "71C" swap pages, then did the exact thing when I put mine together. It's on page 3 - http://zhome.com/ZCMnL/tech/240SX5spd/transmission.htm "When assembling the transmission, I found that having it in 3rd or 4th gear keeps all the shift rods locked so you won't bump the rods out of position and end up with 2 gears engaged and a locked up transmission. If you are in neutral, any of the rods can move. If in 1st or 2nd, the reverse-5th can move and if in 5th or reverse, the 1st-2nd can move."

I spent a lot of time trying to find little things like the chrome piece around the door handle ends, and the little cup at the door latch on the bottom of the door. There are many parts out there but most don't fit right anymore. If the guy has all of the parts saved in boxes you might be fine. People often take their cars apart though, because they look like they're falling apart already. A vicious cycle... Just realized that I never knew how to spell vicious. Thank you spell-check redline.

Are they 240's or 280's? Not the same. Match your parts cars if you're going to use them. You were looking at a 240 a 260 and 280 in your first post. Your parts cars can't match all three.,

A lot of missing parts. Those little parts are hard to find, even if some are in a bag that comes with the car you might end up missing some.

You could measure a valve's projection on that head you have assembled. Then you'll have all of the numbers.

You are the perfect customer . They put a few new parts in, but keep any old ones that pass a test. You can have old parts that pass but are hours away from dying.

Have I been working on your car...? Wait, I use zip-ties.... I guess not.

That's just a reman. Premier Gear and Hitachi are not the same company. Your Oreilly alt should have a lifetime warranty. Should be in the system under your name if you bought it.

You'd have to consider the angle of the valve to get its extension toward the piston but it seems close.

Alternator failure is common. You might be using the wrong FSM. You're looking for ignition ballast and external regulators on a 78. Both not there.

Probably here somewhere - http://www.carpartsmanual.com/datsuns30/Datsun-Z-Index/Body-260Z-280Z/2-Seater

The battery terminals are connected to what the alternator is putting out. It's the right place. Make sure to rev the engine while measuring. Slowly bring up the RPM until voltage stops rising. If it just keeps rising, over 15, you have a regulator problem.

1978 280Z's don't use the ballast. The 15 volts is concerning since the 1978 cars have an internally regulated alternator. Should only go up to about 14.3 or so at most. High voltage can mess up your other electronic parts. The tach jumping is a sign of a failing ignition module or a failing tach. Sending out extra sparks, that the tach can see but don't affect the engine. Probably want to check the alternator first, getting the voltage right might make the other stuff right. Like Patcon says use a voltmeter at the battery, don't trust the dash gauge.

I think that other types of problems might be getting blended together in the comments. With the clutch pedal pushed in the engine is disconnected from the input shaft. So the clutch seems to be right, it disconnects the engine from the trans, like it should. With the transmission in neutral the input shaft is disconnected from the output shaft. since the car moves with the lever in the neutral position, apparently, then there's a problem with the transmission. Here's another possibility - neutral isn't really neutral. I assume that you are assuming that the transmission is in neutral because the lever is in the middle and/or not in one of the gear slots. Maybe the transmission controls aren't doing what they should. Are the shifter bushings tight? Can you get the lever in to any position that frees things up? Maybe the detent pins/balls aren't detenting. Here's another - a broken or loose shifting fork. It might not be releasing the coupling sleeve. If this was the case you might find that certain gear positions actually lock everything up since you'd be in two gears at once. Overall though it looks like you'll have to get in to the transmission to see.

If he's getting actual movement of the weight of the car he has some serious binding inside. Sounds like the shady mechanic. You can turn the input and output shafts by hand, easily, in neutral, with the transmission out and on the ground. There's no way it should move the car at all, unless there's a serious bind-up.

Just a guess but maybe it's a sign that the ZX module is gong bad. Shorting to ground lightly, causing constant current through the tach circuit. If you have a spare module a swap might show something. Or the higher current flow from the ZX module and the coil is damaging the tach.