Captain Obvious

Yeah, it makes perfect sense to me too now, but it would have been better for my self image if I had figured that out before I saw traces on the scope that made me go "huh?" You're not spinning a bipolar magnet past the pickup alternating poles like a generator. You're just moving one of a number of the same polarity pole towards the pickup from one side or the other. I don't know if they are all N or all S (and it doesn't even matter), but all the poles are the same. No, I'm not going to measure dwell as that is more a function of the electronics in the module, not the reluctor design. Also, I don't have a ZX ignition module as it's already been harvested off the ZX dizzy that I have. All I've got is red and green pickup wires sticking out the side of the module. Yes. Yes, you are.

OK, so reluctors and stuff. Here's the pic that started the conversation: And I did check to see if I have a ZX dizzy, and I do. I hooked it up to the scope and the pickup works, but I didn't get to taking pics yet. But in the meantime, I had my own "Doh!" moment... You know all that stuff about rotational direction? It's BS. With the Z distributor, the waveforms look the same regardless of which direction you spin the shaft, and here's the reason: The voltage changes you see on the scope are caused by the changing magnetic field through the wires wound inside the pickup. You approach the pickup point and the magnetic field increases - Current is induced in one direction. You reach the pickup point and the field stops increasing - Current stops. You move away from the pickup point and the magnetic field decreases - Current is induced again, but in the other direction. But here's the thing... It doesn't matter which way you approach the pickup point from, since the pole of the magnet isn't changing, the current will always be induced in the same direction regardless of what direction you approach from. The steep zero crossing will always be in the same direction regardless of the rotational direction. The only way to change the waveform polarity would be to use the other magnet pole (which you can't do) or to switch the wires to the scope. In reality, the only way to change the direction of the steep zero crossing is to swap the wires. Doh! I should have known that... :stupid: The ZX dizzy changes the waveform a little because of the assymetric shape of the reluctor, but the Z would be the same in either direction. Only way to change the polarity is to swap the wires.

I went through the same thing and hopefully you won't repeat my mistakes. There are at least four different versions of that rear window trim. First design - Used up till they redesigned the rear strut towers? Maybe 70-73 and "early" 74's Has a low notch in the lower rear corner for the strut tower Has a hole for the upper seat belt mount Second design - Used when they redesigned the rear struts. Maybe late 74's only? Maybe 75 as well? Has a HIGH notch in the lower rear corner for the strut tower Has a hole for the upper seat belt mount Third design - Used after they moved the seat belt to the strut tower. Maybe 76 only? Maybe 75 as well? Has a high notch in the lower rear corner for the strut tower Does NOT have a hole for the upper seat belt mount Final design - Used when they moved the speaker to right behind the seats. 77-78 only Has a high notch in the lower rear corner for the strut tower Does NOT have a hole for the upper seat belt mount Has speaker holes So getting to the details of your question... For a 77, you definitely need something that has the high notch. If you're planning to use speakers in the stock locations, then you'll want a pair from 77-78. If you're not going to run speakers in the stock spots, then maybe you want a pair from an earlier year without the holes. But be aware that if you go too far back in the chronology, you'll start getting into versions that have the seat belt hole (which you don't need). If you can't find anything without the seat belt hole, you could patch it and paint it, but just be aware that you'll need to do that. If you get really desperate, I believe you could use an even earlier version and extend the height of the strut notch with a hacksaw. Doesn't have to be perfect because that edge is mostly hidden by your seat belt mount cover on top of the strut tower. Here's a pic of the last two designs highlighting some of the features. 77-78 on left, 76 (and maybe 75?) on right:

Rumor? Really? Now that piques my interest! I didn't get the chance to look to see if I had a ZX dizzy laying around, but I'll try to do that tomorrow.

No, Not a Pun. It's a Palindrome! Glad to hear that the head condition didn't ruin your day. I guess I just take stuff like that harder. When I buy cheap used from a junkyard untested, I takes my chances. But when I pay good money for something that's supposed to be rebuilt, tested, and drop in ready? I expect more. Back to the job at hand... A question for the collective. What's the consensus of Felpro head gaskets for the Z? Are they a good choice, or are there better options?

Absolutely. With all that coil ringing being pushed back into the primary side! But do remember... My pic is in the quiet environment of my bench. I could do the same thing and take a pic of a points style distributor using a pull up resistor instead of a coil and I would get beautiful clean square waves. It's not until you put the distributor it in a car and get all that flyback noise from the coil that things get messy. In fact, I wouldn't be surprised if there was some coil noise that would show up in the electronic distributor as well. The ignition module would help isolate the pickup from the coil noise, but I bet $5 that it wouldn't get rid of all of it. In other words, I bet that same pic would look a lot dirtier when taken "as installed" with the engine running.

At the time I took that shot I didn't really care what direction it was spinning. I just wanted to see the wave shape. However... When you look down at the distributor as installed, it spins CCW. I used a drill on the distributor shaft to spin it, and I see no reason why I would have switched the drill to reverse for the pic. So that would mean that the shaft spinning CW as viewed from the bottom would result in the correct spinning direction as viewed from above? In other words, my pic could very well be the correct spinning direction. There's no reason why Datsun couldn't have used the falling edge to trigger. The best edge to trigger something like this is the steepest one with the greatest rate of change regardless of the direction (rising or falling). I'm sure the trigger point is the center of the pulse where the steepest section occurs by the zero crossing. I doubt the triggering is amplitude based, and I also doubt they are triggering on either of the curved lower sloped areas leading up to or trailing where the reluctor passes the pickup. But regardless of the true direction, it's easy to see how changing the polarity would mess with the timing. I might have a ZX distributor laying around... If I do, I'll snap a pic of that output. And I'll be sure to actually pay attention and verify the correct spin direction.

Sounds like good progress. Here's to hoping that everything works out as planned. What brand head gasket are you planning to use? And are you going to say anything to the head supplier about selling you a "rebuilt" head with three stripped out holes in it and a mangled stud? Personally, I'd be pissed.

"doh!" Glad it was that simple!! Don't remember if I was spinning this the correct direction or not, but here's what the reluctor pulses look like. Other direction would be mirror image about Y axis:

I've thought about what the grease does at high temps and spinning as well, and I've come to the same conclusion as John Coffey. I don't think it goes far and it certainly doesn't liquefy. When I took my old rear wheel bearings out, it was clear that the grease never left the immediate areas of the bearings. There wasn't a lot in there and it was all located by the bearings. I had to use mechanical means to remove it. When I put my bearings back together, I packed the entire recess completely full on the first one. Took about half a tub of grease. a strikingly large amount. After I got done with the assy, I tested the turning torque required to spin the hub, and it was too much. I didn't measure it, but clearly way more force than it should take to spin. Like the grease was trying to get out of the way of the balls, but just had no place to go. When I did the second hub, I packed the balls with grease and a little extra and put the thing together. Felt just like I would have expected it to. So based on those results, and because of where I found grease on the original bearings when I did the disassembly, I took the first side apart, scooped out most of the grease and put it back together again. Feels perfect and matched the other side.

Not really sure what you're asking, but here's another description of how the headlight system works... When you turn on the switch on the multi-function stalk on the right hand side of the steering wheel it allows current flow from the battery, through the headlight switch, and to the headlights. Out at the headlights, at any given time, only one of the two beam filaments is connected to anything. One of the filaments is hanging open (no-connect) and the other filament is connected to ground through the beam selector switch built into the turn signal switch on the left hand side of the steering wheel. The filament that will light is the one that is grounded. The one that is no-connect will not light. What your doing when you toggle HI/LO beams, is you toggle which of those two filaments is connected to ground and which one is hanging open.

Oh! I thought it was something functional that you didn't like. I lurk seat swap threads and I've seen some not so good reviews of the Miata seats. My interpretation of the consensus is that they look a lot better than they feel. Especially the first design. My own personal impressions after sitting in them is that the ones you have were undeserving of the bad press. Getting a little off topic now, but I shied away from the Miata seats because of the reputation and am going with Fiero seats instead. Thanks for the feedback and info!

That's a really neat idea.

Zedyone, Any details you can share on what you disliked about the Miata seats?

Well you got it bad, my friend. You know... That car guy thing that makes some of them do weird stuff? You got it bad. Not saying I'm any different. I'm just sad that I didn't think of that TIU mod first. :laugh:

Chas, Did you do that, or are you thinking of doing that? Did you take those pics?

What metal disk are you talking about? Is there a disk in your picture somewhere? Everything looks black... Can't make out any seams. Are you talking about the piston itself maybe? The part that the rubber seal slips onto?

Yup. Like that. You're having trouble finding HD-30? I've not had that problem. I've found that HD-30 is easy to find. What's hard to find is non-detergent 30W. At least in my area.

If your leaning out at throttle punch, then you're going the wrong way with the oil. Ditch the 20 weight and replace with 30 weight.

Yeah. What he said. (Only additional independent thought I can provide is that the piston max rise is NOT simply max RPM. You can easily run the engine up to max RPM by grabbing the throttle linkage while sitting still, and the pistons will not rise all the way to achieve that feat. They will reach max altitude when the engine sucks the most air. Might be at max torque, might be WOT at max RPM.)

Gotha. I just reread what you wrote before and just realized that you had not made any mods. You just thought about making mods but didn't actually make any.

Or: or a hat or a brooch or a pterodactyl.

Agreed. And that also falls in line with what I mentioned about the races being press fits, but not as tight of a tolerance as other bearing press fits I've messed with in the past. It's clear that they designed the system with the intention that you could do things your not normally supposed to do (like apply force through balls) without destruction. That said... When I put mine back together with my new bearings, I worked up this weird fixture contraption with custom ID tubings and drifts, etc. that allowed me to press the assy together and still follow traditional "don't put force through the balls" rules. Was it a pain in the arse? - Yes. Was it worth it? - I wouldn't if I was on the clock. I would just do it simple like they say in the manual. Would I do that again on my own car? - Probably not.

In theory, "No". Reason being, there's no way to get the outer bearing off the shaft without putting force on the balls. You see, when you install bearings, you're never supposed to use the balls as part of the force path to install them because you run the risk of damaging the balls or the race. You're supposed to only press against the race that is being forced into place so that no force goes through the balls. In other words... When you install that outer bearing onto the shaft, you're supposed to press only on the inner race as it slides against the shaft to it's fully seated position. Works fine for installation of that outer bearing, but you can't get around to the other side to grab the inner race when trying to disassemble. HOWEVER!! When you pull that stub shaft out of the housing, you'll be looking right at one side of the balls of that outer bearing. You should be able to get most of the old grease out replace with fresh without ever taking that bearing off the shaft. (And as a side note - At least on my car, that outer bearing is not an incredibly tight press fit against the shaft and mine came off easier than a lot of other bearings I've messed with in the past. With the relatively small amount of force I had to use to get it off the stub, I would have been willing to put it back into service without fear that I dented the races.)

So about your Miata seats... I can see the top of one of them in the background of your pic. Why did you hate them? At the last local import show, I went walking down "Miata Road" looking at the seats. Info was sketchy and hard to put together, but I believe there are (at this date) maybe four different styles? First - something like 90 to 98 Second - something like 99-00 Third - something like 01-05 Fourth - 05-present I think yours are the second generation. A couple generous Miata owners also offered me the opportunity to sit in their seats, so I have some seat of the pants impressions (get it?), but I want to hear yours.