Zed Head

The E12-92 has an extra pin that adjusts timing through a temperature switch. Might be that when you switched to it you inadvertently changed your timing. I thought that you had an E12-80. There's not really a good reason for a performance change unless the E12-92 is failing, or something else changed. p.s. some people say that you have to short the extra pin to ground or run power through to stabilize the timing. The 280ZX FSM probably shows how it works so it could be figured out. Really though, you're about ready to just move on from the old Nissan parts. I'll just pile a couple more things in here for anyone with an E12-92 in the future. Notice the idle switch and the thermo switch connected at the "IC". Somebody with electronical experience might have fun figuring out what Nissan was doing here. Last, maybe, edit - here's a zcar.com post from way back, with a reference to 240260280's friend Wayne Monteath. Apparently, it doesn't matter if the extra pins are connected or not but the question would be where your initial timing is when you switched. https://www.zcar.com/threads/e12-92-or-e12-80.116513/

This one is already up to $15,000. Funny though, the guy has been driving it with no air filters. Had the carbs rebuilt, just never put the filters back on.

This modified 71 is probably going to outdo the "early 71 Series I" 240Z. It has fender flares! Eeeewww.... https://bringatrailer.com/listing/1971-datsun-240z-231/

$12,300, RNM. Presentation is key on BAT. The seller did a not-so-good job.

I think it has something to do with the way the fuel is metered from the carburetors. With EFI the air flow is fairly precisely measured and the appropriate amount of fuel is added to balance the air. With carbs the fuel is pulled up from the float bowls and basically spilled in to the air stream. There are emulsion tubes and other things but still the fuel gets pulled up in to the air stream, more air = more fuel. If you have pulses of air from a lumpy cam (inconsistent air flow/vacuum) the fuel gets bounced up and down and accuracy/consistency is lost, plus the fuel does not stay well-atomized. Carbs work best with smooth air flow through them. EFI averages out the pulses back at the AFM or MAFS so is not as affected by a lumpy cam. That's my basic understanding.

The 70/71 is up today. Let's see what the collectors think, if any are interested. https://bringatrailer.com/listing/1970-datsun-240z-82/

You're saying that a 1973 240Z has the same value as 1970 240Z? That if you had a 73 you'd trade it straight across for a 70? Because they both say 240Z on the outside. Trying to use those played out memes will drag you in to absurdity. Be careful.

Actually, my post wasn't about the easiest way. It was about the best way to be sure both ends were correctly seated. Your bobbly speedo sounds like the cable is not fully seated and it's rubbing on the inside of the sheath. It's bound up. Or it might be that you have a bad spot on the gears. At least you know that the parts all work.

Yes and yes. There are two possible reasons that the cable is not spinning the speedo/odo parts. 1. There's enough slack in the sheath that the drive cable can get jammed up and not engage correctly. It helps to pull the inner cable out at the transmission and stick it in to its slot on the transmission end then push it back up toward the speedometer as you screw on the sheath end. At least that helped me. Apparently the speedo end seats more easily than the transmission end. I think that I had also spun the propeller shaft while I did that. I had the back wheels up. 2. The housings are different. The locking slots are oriented 180 degrees apart. The gears are offset so if you use a ZX in a Z the gears won't mesh. Look in the hole and you should be able to figure out which one you need. You can also reorient it without locking it down and see if it engages. Some people just grind a new slot in the housing when they do a transmission swap. But it's pretty easy to swap the gears too.

That's the original round style that they used on the 260Z's. The 280Z's used the rectangular one like in the drawing you posted. It looks just like the drawing. It's folded over then taped up, so it's a different shape of lump.

I had a similar thought. Or put some colors/label on the wires and the module pins. I had a module crap out on me in my garage after some engine work. Forgot to put two plug wires back on. So they do fail for various reasons, but so do the originals. I carried a spare module and the tools need to change it in the car. I also had a spare ECU behind the seat.

There's no need to get it out. Just verify that the lump is there. If the tape is unmolested you migth as well leave it. Remove all of the existing wrongness and see where you're at.

It's a lump in the taped up harness. Like a frog in a garter snake.

Av8ferg solved his problem in this thread by swapping coils. Not really clear why that worked but it did. Like SteveJ says though, the old TIU should be completely disconnected. The wire to the tachometer is a branch off of the blue wire from the engine bay. It does not run through the old module. And the 2.2 kohm resistor is in-line buried in the wiring on the way to the tachometer. You should be able to just connect the blue wire in the engine bay to the coil negative, disconnect the old module, and have everything working correctly.

Way back...

Here's some brochures from around the same time frame. https://www.gmheritagecenter.com/gm-heritage-archive/historical-brochures.html

Hope so. Seems unlikely though, doesn't it? Hopefully they fixed the root cause. Should make a huge difference. That was a lot of slop. The bonus is that you found those other problems while looking for that one.

Model years had been a thing in the States for many years before the 240Z appeared here. Any kid growing up here knew all about 55 Chevys and 67 Camaros and 72 Cuda's and 69 GTO's. You could tell a 68 GTO from a 69 by its tail lights. Same with the Chevy's. Even the tail-light lenses of the Camaros had a date stamp molded in to them. It was a point of pride to be able to tell a model year at a glance when you saw a cool car. HS30 seems to be saying that other countries don't define cars by year. Apparently a "model" exists as an entity through many years and changes are implemented as needed or desired, at any time during the model's production. I did not realize that the States is the only place that defines cars by model year. Interesting fact, I learned something about the rest of the world. Nissan did catch on to the model year nomenclature by 1973, apparently. They changed the wording of the Foreword in the Service Manuals. Here's 72 and 73.

Any chance that the noise is actually from a failed differential or mustache bar mount/bushing? The diffs are inherently noisy. If you have any spare differentials you could swap one in and see if there's a change. Or take a hard look at the mounting areas. On deceleration the diff nose is pushed down. And the metal edge of the diff mount is very close to the crossmember. It's easy to imagine that the edge of the mount contacts the crossmember on deceleration. Borrowed a picture from somebody's web site.

Even that link you posted isn't working. It's a shame that they kept taking people's money for so long. I wonder how many people will get screwed. https://whiteheadperformance.com/

Bad? It's terrible. You really should put your car details in a signature. It's PITA to search around to confirm what people are talking about. Your 280Z should not have replaceable u-joints. Those clips holding the caps in should not be there, they're not even Nissan style. That is an aftermarket shaft or somebody has modified the staked shaft that came with the car. Might be why the u-joint failed and it might still have a vibration after you install new joints. I'd get a new shaft or a used 280Z shaft. Watch out for 1975 shafts, they're different.

I should rephrase the question as "what did Nissan change on the 240Z when they started selling them as 1971 models?". So far, everything seems to show that the cars stayed the same until HLS30-21001 arrived. The "late model 240Z". That a late 1970 and an early 1971 are identical. This conversation started because the guy on BAT called his 1971 "titled" 240Z a 1970 240Z. It seems that the only difference between his car and a 1970 titled 240Z is...the title. The whole thing is not about the physical car but the ink on a piece of paper. If he didn't have the title and a person (maybe a car show judge) couldn't see the ID plates or VIN stampings, there would be no way to tell that it was titled as a 1971. It's identical to a "real" 1970 240Z. That's what I was trying to figure out. In effect, Nissan did not introduce the 1971 240Z until HLS30-21001 seems to be the conclusion. The cars sold before then were just 1971's in ink terms.

For the record that is actually Carl Beck's quote from his zhome page. I copied the text.

Stuff to ponder. 1. Model Year: This is a marketing term, usually it is between 8 and 12 months long and within which, a specific model is considered to be "current". In the U.S. new model introductions in the 70's could take place as much as four months ahead of the beginning of the calendar year. That is to say, the 1971 Model Year Chevy's were introduced to the public and put on sale in Sept. 1970. (in the 90's manufacturers were pushing that new car introduction to as much as 8 months ahead of the calendar).

There's probably a Service Bulleting for 1974 changes too, I'd assume. You've kind of skewed my point. It's not about introducing a new model mid-year. It's about what defines the model. The basic point is, as you've shown, is that Nissan has defined a "1971" as having certain features. Different from a 1970 model. They listed all of them and defined them as "late 1971". By Nissan's own words the guy on BAT could argue that his car is actually a 1970 "model". Nissan seems to be saying that they didn't change anything until late 1971. There is no "early" 1971 240Z. Only 1970 240Z models made in early 1971. I saw your comments on zhome about when Nissan switched but it's not clear how you know that.