Captain Obvious

Working on it. I was originally driving different modules using a signal generator, but after messing around with that a bunch, I'm thinking that it's not a good representation of the real world situation, so I'm going to have to figure out a way to use a real VR signal. First attempt at setting something like that up worked OK for speed control, but I was using a variable speed DC motor to drive it and I was getting huge amounts of noise on the system. I need to come up with something quieter. Basically, you're asking if I can illustrate the timing changes @Av8ferg saw when he swapped from one module to another, right?

So here are a couple things about the 77 and 78 modules: The cases are electrically isolated from everything inside. In other words, there is no electrical connection to the metal boxes that house either the 77 or 78 module electronics. There is no current limiting in the 77s output stage. That is why a ballast resistor is required to limit the coil current. The 78 module, however, DOES have current limiting built into the output stage which is how Datsun was able to get rid of the ballast resistor for 78. Other than that current limiting and some temperature compensation (which the 77 also does not have), the electrical designs of the 77 and 78 modules are pretty much the same. Since everyone likes pics, here's a pic of the 77 module guts: And here's a pic of the 78 guts:

Sure I'm taking questions. Admittedly I'm having a little trouble figuring out the best way to organize my thoughts for this thread. I've done a bunch of analysis of a couple different designs and I'm trying to do a knowledge dump. Problem is I'm not sure the most effective way of getting info out. But absolutely questions would be most excellent.

And for discussion, here's what happens if you get the distributor input to the module reversed somehow. Note that the module still fires a spark on the negative to positive transition, but the slope of the input signal at that time is very gradual. Not good for spark scatter and consistency:

I've been poking around with the ignition electronics on and off and there seems to be some interest in getting into some of the details of how things work. So here's a place to start. Here's a pic of the ignition module signals. The input signal from the VR distributor is in blue, and the output signal that drives the coil is in yellow. Note that when the yellow output signal is low, the coil is charging (dwell), and when that output signal goes high, the coil would fire a spark. Spinning the distributor (by hand) the signals look like this: First think to note is that the ignition module (1977 style) fires the coil on the negative-to-positive (N-P) transition of the VR input signal. Also noteworthy is that the triggering N-P transition VR signal is a steep, almost vertical, slope. This is important because the steeper the slope here, the more consistent the timing will be with less ambiguity and spark scatter.

Not quite sure I understand which tach you have (it appears you have two of them?), but the correct tach for your 73 is the style with the loop on the back. The other style (without the loop) will not work in your car without some other modifications. This is the correct style for your car:

I will get my geek on and start a thread about such things.

https://en.wikipedia.org/wiki/File:Hamilton-appealing2.jpg Hahahaha!!!!

I will check a couple of the distributor mounted matchbox modules when I get a chance. I've got a couple tossed in a box that came from who-knows-where. I'm sure some of them work. Probably. Maybe? At least at room temperature.

I did the same digging you did and that page turned up on my radar too. On that page they indicated that the simpler 4-pin GM HEI module used a positive transition, but the other later modules used positive to negative. I have not verified this myself, but they say: "The 4-pin HEI uses a negative-to-positive transition, while the 7/8-pin uses a positive-to-negative transition (though this *might* have changed in some applications). Thus polarity of the reluctor signal is critical to proper function." I've poked around a bunch with the Datsun modules they put by the passengers feet (up through 78) and those fire on the rising edge of the VR pickup. I've got a couple of the later matchbox ignitors here, but haven't checked them. Here's a couple pics of ignition module waveforms. This is a 77 module being driven by a ZX distributor (so the shape of the VR is a little different than previous years). This should be about 6000 RPM engine speed. Note that when the output signal goes high, it releases the coil and initiates a spark. You can see that it sparks on the rising transition. And here's a 78 module om my newer digital scope. Note that I'm not using a real VR input on this one, I'm just using a signal generator to provide a simulated input signal. But the important part is that it also fires on the rising edge. This is 6000 RPM. I know we are getting off topic here and if anyone wants to get all real geeky with the ignition modules, let me know and I can start a thread with that intention.

Well you were doing great until the part about bending the arm a little. The tension in that arm affects the accuracy of the gauges. Don't know if you bent it enough to cause things to be inaccurate ,but a working (but inaccurate) gauge is probably better than one that doesn't work at all, right? You see the little set-screw threaded into the regulator contact? That sets the pre-load on the contacts and is used to calibrate the regulator. Let's just hope yours is still good enough.

Another data point... I found the Canadian version online and the UPC is: Model Number: 264656 UPC: 020066217174 While the back of the can I have here is >> UPC: 020066210137 Again, not to say they aren't the same, but can't confirm that they are.

Now as for the details about the part number... That's no fun. Gives me less confidence that it'll be the same. Not saying it's different, but just saying I'm less confident that it'll be the exact same thing I have here. Wonder why it's a different number. The SDS sheets are pretty much identical for the two numbers (264656 and 261413), but that's not a guarantee either. In any event, if you can turn up a can of that spray, give it a shot and let us know if you like it.

Absolutely I did. I'll fix that now before I confuse anyone else.

That's a really good point there. You set the base timing using one of those two modules, but there's really no guarantee that the output timing from the other one will be the same. Could simply be that the propagation delay through the modules are different, or it could be something way more significant than that. I know that GM put a "cranking mode" base timing setting into a lot of their later modules used as a bootstrap mode to fire the ignition before the computer was able to take over. Now that's for the later modules that used an ECM to control the timing after the engine was running, but they may have put something like that in the earlier simpler non-ECM controlled units too. And if they did, the question is... How does that relate to the rotational position of the VR pickup titts? And now that I'm thinking about it, I thought of something else... I know the earlier modules (up to 78) fire directly when they receive a pulse from the VR pickup, and they fire on the rising side of the VR signal. Many (most?) of the rest of the later modules fire on the falling edge? I don't remember what GM did, but I will look into it. I should have thought of that before. Arrgh. Bottom line is put a timing light on it and see if you're OK. You might have to pick one style as primary and the other as 'backup only".

@CanTechZ Unfortunately lighting can play such a huge role in how things like this look, especially in pictures. It's really hard to do comparisons with one variety and another. If you can get your hands on a can of that Rust-Oleum 261413 Metallic Carbon Mist, give it a try on a test piece and see what you think. I had my taillight panels completely done, clear matte coat and all, with the Ford Dark Shadow and I was never completely satisfied. That Ford color is really good, but I think the 261413 is better. Give it a shot if you can find it. I bought some very thin aluminum sheet and I use that as my test coupons. I used to do it with cardboard, but the textured surface of the cardboard did not give accurate results.

The amount of movement in the regulator is so small that I'm not sure you would be able to see it opening and closing. I would try cleaning the contacts before giving up on the gauge. Gently open the regulator switch contacts just enough to be able to slip a piece of paper (white printer paper) between the contacts and then let the contacts close on the paper. Drag the paper back and forth between the contacts a couple times and see if the problem goes away? Like this:

I know practically nothing about A/C, but I have two thoughts: First is about the leak seal... I don't know any mechanic ever who has even remotely liked any of the sealing additives in anything. Tires, radiator, A/C. Anything. Ever. In fact, my local pro says he won't even evacuate a system if he's told that it has some sort of leak stop in it. Won't put his machine on it. Second thought is about brazing the leak in the condenser. Again, I'm no expert, but there's no way I would try that while the system had refrigerant in it. The pressure will just blow the braze material away from the hole, and even more importantly, you absolutely do not want to light anything fluorocarbon on fire. Bad idea.

Here's a couple pics of the can. Duplicolor 261413 Metallic Carbon Mist: I tried two varieties of matte top-coat and didn't find much difference. I tried Rust-Oleum Matte Clear (#285093) and Krylon Colormax Flat Clear (#53530). Of those two varieties, I found the Krylon to be a tiny bit more flat than the Rust-Oleum, so I went with the Krylon.

Bottom line? Duplicolor 261413 Metallic Carbon Mist. Top coat with Krylon Colormax 53530 Flat Clear. More detail? My first attempt was BFM0360 Ford Dark Shadow Gray. The basic color was good, but it really lit up when light hit it. In other words, it looked pretty good in certain lights, but in other more direct light, it didn't look so great. Looked way too light. My second attempt was Duplicolor 244228 Metallic Charcoal, and pretty much the same problem as the Ford Dark Shadow Gray. It looked good in the shade, but when light hit it from the right (or wrong?) angle, it was way off from stock. My third and final attempt was Duplicolor 261413 Metallic Carbon Mist. I found this paint looks good in both sun and shade and does not "light up" like most of the other metallic options (like the Dark Shadow Gray). I would recommend this color over all of the other previously discussed varieties. Of course, it really doesn't mean much unless I could compare it to a stock colored panel, but I don't have one here. Anyway, it looks like this. This is in the shade with no flash: In the shade with flash. Note how the reflectors in the taillights and the license plate lit up with the flash, but the panel did not: And in the sun. Half direct sun, and half shade-ish:

I redid mine three times before I was satisfied. Let me know when you are ready to do it again.

Nice. That should help restore some confidence in the ignition system!

Well it's not simply an implication anymore. I've poked around inside the 78 module enough to determine that they DID incorporate current limiting technology into it. 74-77 did not have current limiting, but 78 did. I have no doubt the 79-83 matchbox modules incorporated current limiting as well.

LOL.

There you go. That's what's going on with the power regulator! Other than the mass jumble of extra wiring nest in the back... You could have cleaned that up to make it simple enough that it looked we.... simple. Thanks Steve!