Zed Head

From my view, the onus is on you to provide the data from the instrumented testing or a link to someone else's work, from an engine with the heater core supply line back to the radiator or the thermostat housing. You're making unsupported claims. Thought experiments. Conjecture. Supply the data, or the link to the data. It's just a BS session without it. Edit - Just to simplify - what we're really talking about here is the difference between drilling holes in to the cooling passages on the driver's side of the head (left) and plumbing that coolant flow to the thermostat housing versus just running the heater core bypass line to the thermostat housing instead of the heater core. That is the heart of the discussion. Much much easier and cheaper to just run a hose from the fitting already installed at the back of the head. Why isn't that the answer to the problem? That's the question that needs real data.

The 260Z's apparently are known for having weak voltage to the starter solenoid. Some people recommend a relay to get full battery power to it. Here's a couple of links describing a solution - "Click, Click - No Start" Fixed!! Tony D - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z Ford Starter Solenoid? - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z Of course, if your battery is weak, the problem gets even worse. Are you sure it has a full charge?

You would most likely be fine to just block both passages off completely. I started a new thread with pictures to show how the coolant gets to the heater core supply passage, for mine and Leon's discussion, and anyone else who's interested. The heater core supply passage is really most like an after thought to get hot coolant to the heater core. If the passage is blocked the coolant just flows back up the head to the thermostat with the rest of the coolant. http://www.classiczcars.com/forums/engine-drivetrain-s30/49177-head-cooling-what-i-talking-about.html#post428557

Started a discussion over on Stanley's thread (link below) about bypassing the heater core and its effect on cooling. http://www.classiczcars.com/forums/interior-s30/49100-dump-heater-keep-fan.html#post428554 Didn't want to muddy up his thread so I've posted a couple of pictures I took to show what I was talking about over there. The first shows the large passage at the back of the head which should flow a lot of the coolant up through the block and through the head from back to front. The heater core supply hose fitting has been removed and is lying on the head. The second shows my finger in the big passage and visible in the heater core supply passage. That's what I think would be the shortcut for the coolant if a large hose is attached to the fitting and coolant allowed to flow freely. Only posting for the record and the discussion. Not trying to win, it's just an interesting topic.

I can't agree. You're inferring from very little evidence. There's no real difference in flow through the head determined by where the coolant goes, whether it's back to the pump inlet or back to the radiator. In effect, going to the pump inlet pumps less water through the radiator. If the flow through the engine and thermostat was barely enough to remove the heat produced, you could argue that diverting hot water back to the inlet pushes things over the edge. But I haven't seen enough real evidence of why the overheating occurs. Most of the theories suggest that "spot boiling" over 5 and 6 is the initiation of a reduction in cooling capacity overall which then leads to overheating in general. The hole drilling and plumbing is intended to move more water over 5 and 6. I understand what you're saying I just haven't seen real evidence for it. Even in all of the pages of the head cooling thread on Hybridz. Lots of conjecture, some experiments with hole drilling and re-plumbing and some subtle results, but little understanding/explanation of what's really happening in the engine and head. If what you're suggesting is correct, then my statement about running the heater core supply back to the radiator directly would be a good idea, and cheaper than the hole-drilling an re-plumbing . Maybe it should be suggested over on Hybridz. It would be a lot easier than what's being done now. Edit - Sorry Stanley. This topic has generated a ton of discussion on a different forum. I'll stop now.

Sorry Leon, that's not the way I interpreted the results. People are porting the driver's side of the head to reroute coolant flow, but nobody is just running a big hose from the heater core supply line to the radiator. There's a dead zone in the head. Bypassing the heater core, wherever you end up directing the coolant, makes it worse. The coolant comes up through the block and leaves before passing over the combustion chambers. That's my take on it. I could be wrong. Unless all of those guys just missed it and they're drilling all of those holes for nothing when there's a big one already there. Edit - here is Tony D's post on the comparison of blocking the outlet versus looping (bypassing) it. I may have added my own twist above by inferring (through lazy thinking) that the bypass direct to the radiator would cause the same issue. But that's part of an ongoing separate discussion. This work applies to what you're doing - Looping the Heater Hose - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z

I'm no expert on how these engines work but the guys who modify for more power and/or race have shown that allowing coolant to flow at a high rate out of the back of the head back to the radiator will cause imbalanced cooling and increase the chance of overheating. The heater core only bleeds a small amount of the flow that is passing up through the block to the back of the head then forward to the thermostat housing. When a hose is run directly from the back of the head back to the radiator, flow through the head is diverted. Most recommend blocking the port at the back of the head instead of rerouting it. This forces the coolant to pass through the head as designed, removing heat along the way. Just passing on some knowledge from other forums.

I've had great luck with hosing down sticky electrical switches with CAIG Deoxit - Home - CAIG Laboratories, Inc. You can get it at audio places like Guitar Center. Other contact cleaners might work well also. The switches are difficult to diagnose because some do their job by grounding a circuit and others by supplying power to a circuit

The engine sounds great and I like the old weathered survivor look of the paint (seriously!). I notice the your engine seems to move with a slight rev in neutral. Curious, did you install new motor mounts? Not to pick at it, it just seems to move more than mine. Could just be the angle of the video. But under load it probably will move even more. It'd be a shame if you've got a motor mount about to let go.

Is it, or has it been, an automatic? They have an "inhibit" switch that gives problems sometimes. Here's a link to the 1976 wiring diagram, that a member here put together - http://www.classiczcars.com/forums/open-zcar-discussion/36494-free-full-color-wiring-diagram-1976-280z.html Might help you trace the connections. I think that 75 and 76 are similar. Looks like power comes right through the switch and all the way to the yellow wire, passing through one connector on the way. It could just be the mechanical part of the ignition switch. I had to put a little extra twist in the rod that actuates the electrical part of the switch to get mine to work. You have to take the switch off of the column to check that.

So it starts now, but takes too long... If you end up in the wrecking yard looking for a switch, the easy way to tell is the size of the flats (the part you put the wrench on). Look at BGM's links and you'll notice how long the flats are on the thermotime switch, compared to the others. The other switch in switch in your picture is for the second magnetic pickup circuit in the earlier 280Z distributors. The wire always breaks off of them.

Many people remove the CSV parts. I've removed mine, the switch and the valve both. It's kind of a luxury for a super quick start. Unless it's really really cold out it barely makes a difference. Are you having problems or just getting things back together?

I would confirm that you have a problem first. "Engine spinning fast" doesn't tell much. Check cylinder pressure, or pull the valve cover and check your valves and keepers. Check the cam position at TDC via the notch and groove. Might not be a chain issue at all.

The top one looks closest but still doesn't look like the thermotime switch (not sensor). It looks more like the CHTS, which BGM linked to. I have both, the thermotime switch is squared off and one piece, while the CHTS has the tapered tip and is two piece. You shouldn't have a CHTS unless you have a ZX engine. The thermotime switch will measure ~60 ohms through the two pins when cold. When it's hot it will open up.

Are you sure that the original one from your 71 won't work? Odds are fair that it might. You might have to remove the dust cover. When you said "yoke" I thought that you meant just the piece that slips on to the trans shaft and has the u-joint in it. Some people call it the slip yoke. You're asking for the whole front half of a two piece drive shaft. I don't think that they exist for a 240Z. Someone out here has the answer.

I misread the transmission part number. Thought you were modifying a newer transmission, from a 300Zx or 240SX, which also would require the older 70-71 shorter drive shaft. I think that any of the yokes up to mid-74 might work. Late 74 or 75 is when they went to the staked u-joints. Anyway, good luck with it.

Your dash ammeter will give a good indication of whether or not the alternator is charging. + means charging, - means discharging (running off of battery power). This would be while the engine is running, when the key is off it should be in the middle. Car batteries don't like to be fully discharged, it's not good for them. It's also not good for the alternator to charge a completely dead battery. You might have a bad battery damaging your alternators. And, as Steve implies, if you haven't rewired the car for the internally regulated alternator things won't work right. Also, for the record, the ZX alternator is probably 60 amps, not 70. The 280ZXT's (turbos) came with 70 amp alternators but they're not available anymore. The parts stores replace them with 60 amp alts. If you're no good with wiring, and find that your battery is bad, you might be best off having the old external reg alternator tested and, if it's good, getting a new external regulator. One option.

borini63 parts out a lot of cars. He wanders around all of the various Datsun forums. Might be worth a message. He's a member of this forum. Have you swapped the bell housing yet or is it already done?

You know more than I do. I missed the monitoring function. I thought it was like the coolant temperature sensor, just off and on. Didn't know the EFI ECU was that sophisticated. Maybe it just needs a good Italian tune-up.

Thought you had the ECCS since you said "blinking". I don't think that the EFI system is "monitored" periodically like the ECCS appears to do. I think that the EFI lamp only glows when the O2 sensor is hot and the O2 level is above or below the narrow band threshold. That's why the FSM has you ground the sensor connector while watching the lamp. That mimics hot and either lean or rich (can't remember which) condition. If you ground the O2 connector and the light glows, then disconnect it and it goes out, that means the harness and ECU circuit are O.K. The lamp probably doesn't go on during normal usage until the manifold is hot and the lean or rich condition is met. Just a guess, I have a 76 with no O2 sensor. Hopefully I'm not confusing things.

Weird, you must have found it through Google or some other link. If you try just Web Page Under Construction it doesn't work. Pretty basic stuff though, hard to go wrong unless you adjust the spring when it doesn't need it. On the blinking light: Are you not trusting what the FSM says? Page EF&EC 47 > if "N.G." (no blinking light), test the O2 sensor and the harness. Did you do the tests on page 48?

Nothing will work right if you don't have the right fuel pressure. I'm not familiar with any AFM rebuild procedures and the kamikaze link is "under construction". The insulators are there for vibration and heat insulation. The smaller o-rings at the bottom are vacuum seals for the intake manifold. The cracked insulators won't affect the way the engine runs. I would check fuel pressure and flow before going too much further.

Is the gear assembly sticking out sideways or straight up? Maybe the shafts are hanging from the gear set weight and causing misalignment. It's pretty easy to stick the front case back on though and find out what will happen in use. I would do that anyway without sealant just to make sure things are right. I had one on and off several times and wished I hadn't been so confident with the sealant. Had to clean it up and start over. Don't forget to put it in to gear before putting the front case on or you'll probably lock it up when it goes in to two gears at once.

Something off with the shift fork? Apparently they can bend or crack without breaking completely. The roll pins holding the fork on can shear also, maybe yours is halfway there. The fork might be directional also. Have you seen duragg's rebuild opus on Hybridz? Might make you want to spend a little more time on it before you put it back in. High RPM shifting dynamics - Drivetrain - HybridZ

The thread title recalls a scene from a popular old movie -