Zed Head

Funny, but the GM people call the reluctor, the metal piece with six outward pointing projections, a "timer core". And the stator (the ring in the ZX distributor with the inward pointing teeth, a "pole piece". And I thought the weird simple names in the Nissan manuals were from translation issues. Here's a picture of the Z and ZX reluctors showing the different shape of the ZX's. The GM timer cores seem to look like Z parts, with no fancy shaping. The ZX part has a ramp up to the trigger point, CCW, top-view. Here are some links to other reluctor images, various manufactures. Odd that the ZX is different. Geek stuff. http://www.junkyardgenius.com/ignition/chevy/magcon01.html http://myplace.frontier.com/~wgmumaw/Distributor%20Conversion/DistributorConversionBills.htm http://www.lindertech.com/bhrs/chev_8_dist_elec_conv.htm http://www.msdignition.com/Products/Distributors/Acc_/8415_-_Reluctor,_Dist,_CNC-Machined_Billet_Steel.aspx

Odds are it's these specs. on a six cylinder shaft. 311F Datsun 4 Cyl Camshaft

Realized that we were about to put a serious hijacking on to Eurodat's thread here - http://www.classiczcars.com/forums/electrical-s30/52621-fitting-hei-module-transistor-ignition-unit-1977-280z.html#post459983 Started this new one. Here's a link to a post showing the reluctor output from an 85 and an 88 Jaguar, which apparently used the GM HEI module in their ignition system. Looks similar to CO's Post #15 (to my eyes) in Eurodat's thread. Sean's Jaguar Tech Pages - Lucas Digital P (HEI-based) Ignition Diagnosis

Alright, no problems. If your problem were mine, I would make measurements along each point of the ignition circuit with the key On. What you should see: Coil positive - battery voltage Coil negative - battery voltage Ballast connection from coil negative - battery voltage End of blue wire from ballast connection - battery voltage. As I said, that's why I asked about coil positive. It's a key measurement. If you have power to coil positive with the key Off and none with it On, that's a big clue. Best time to do it is now, with the module disconnected. If you get bad measurements with no module in the circuit, it's not the module.

Here's an article that will probably make much much more sense to you than me. The comment about the reluctor is at the top of page 3. From the article (by Lou Dudzik) - "If a reluctor of different design is used, the dwell may end up longer or shorter than the ideal time. The HEI reluctor rotor is comprised of a wheel with short-duration spikes on it. If a rotor is used with long-duration ramps before the spikes, the bias voltage on W may increase too much, creating the aforementioned stumble at higher RPMs." Somewhere out there also is a thread about how the ZX distributor is better for high RPM. Not clear if the poster is talking about the module, the distributor or the combination. I'll post it if I find it. I also had a conversation with a guy about the ZX module was better, for him, than a GM HEI module, when used with a ZX distibutor. So it may be that the ZX reluctor's different shape is actually bad for the GM HEI, but the Z's is good. That would be nice to know. He said that he was going to get some traces but he never came back. It was on Hybridz. All I know right now is the Z distributor works great with the GM HEI module. If the ZX has the same waveform it seems reasonable that it would to. In over my head... Edit - I started a new thread just to focus on the odd bits about the HEI module. Didn't want to load up this thread. They re neat little devices and people are using them for all types of ignition systems, from motorcycles to old muscle cars. Here's a link to the other thread - http://www.classiczcars.com/forums/electrical-s30/52651-gm-hei-module-odds-ends.html#post459994 HEI Notes - Dudzik.doc

Hideous bumpers is late 260Z, isn't it? How does one get power windows and door locks? Are those factory options?

Well, another perspective might help. I'll bail out. The capital letters show some aggravation. In parting though, I feel compelled to point out that, at the least, the first statement above with a measurement is incorrect. There should not be power to the blue wire at the TIU with the key off. That's not right, and might be a sign. I know this is correct, but went out and measured my coil negative now just to be more than sure. Good luck with it. "At off I get 12v to it from the battery as suggested is correct."

Is that with the wire connected or disconnected? Sorry, but these things make a difference. What you might be seeing is voltage from a pullup resistor in the module, that goes away when the other side of the transistor gets power (full disclosure - I don't really know about this). Transistors and the way they're used is not typical electrical stuff. I'm just trying to get you to something that makes sense. It shouldn't be that hard. If you're tired of my comments, I can bow out. I asked about the positive terminal on the coil because it should be connected to the blue wire you measured, through the coil. Module-blue wire-ballast-short blue wire-coil negative-coil windings-coil positive. If you don't see the same thing at the positive terminal it will give you a clue about where the break in the circuit is.

It's not clear where you're measuring. Blue wire at the module, at the coil, at the ballast, or the mystery blue wire? Does anything else that should have power not have it when the key is On? Like the positive post of the coil?

Did a piece of the head casting break off or did the liner just work its way out if its slots? A closeup of the damage would be interesting. Your problem is the reason that some people recommend avoiding the N47 or P79 for use with turbos.

Good point and clarification. I made an assumption from a collection of french model statements, off the internet. The HEI module only has G and W as pin ID's anyway, with W identified for "positive" from the distributor in the various writeups, but G and W are just GM wire color letters (green and white). I think that people just used positive because the correct wire from the Nissan distributor is red. In retro, when I first got in to the HEI game, I remember wondering what "positive" really meant since each wire sees both positive and negative current. "Direction" is different but I don't know what the proper name for that is. Even rising and falling don't mean much. The ZX trace will be really interesting. You might start a run on ZX distributors if a performance benefit is found. There's definitely a rumor floating around out there but no data.

Apparently you can remove the liners. Some do, for the general bigger-is-better concept. But the remaining hole is probably not good for flow over the normal RPM range. It has no shape. Somebody did some flow-testing on a variety of heads and found that the liners didn't hinder flow, on a stock N47 head. I would be concerned about an imbalance between cylinders. May not be a real issue. I've never heard of anyone using a head after they discovered a liner fell out. Pretty sure that they're cast-in. Maybe someone could weld the broken aluminum piece back in, if that's why it fell out.

This is probably the key statement. I bought my car because it was straight, non-dented and mechanically sound. But it didn't run. Because I was looking for a garage project and like the mechanical, electrical, mostly engine-based things. Hate bodywork. I was actually thinking about a small-block chevy swap and only got the engine running for in-the-meantime. If you buy a car that's too complete, there won't be anything to do to it.

It is just a theory. Nissan may have become aware, but they didn't fix it. Pathfinder VG30E's have a similar problem. Broken studs, snapping at the head surface. Mine sounds like crap, I wish I lived by a Nissan executive's house so he could hear it every day. They're a pain to work on.

Pretty cool. I think that might be backward since the 4 pin module triggers "going positive" (according to the Megamanual - link below). You can see how timing gets all screwed up if the wires are backward. The zero-crossing is pretty broad. You don't have a ZX distributor do you? It has a different-shaped rotor. I've read some things that imply the ZX distributor has better high RPM dwell. I wonder if the ZX rotor shape gets the signal above positive quicker so that it can start charging the coil again. I'm assuming that the trace has to be in a certain region for charging to start. Could be wrong. General Motors 7-pin HEI Ignition Control

The dimmer switch is actually at the base of the turn signal stalk. The parts that you're showing in your picture are the switch assembly (two switches on one board) that supplies power to the headlight circuit and the running light circuit. Notice in SteveJ's first FSM copy picture that someone wrote in "ground". RB and RW are grounded there, one or the other by the switch at the base of the turn signal stalk. I've fixed a problem like yours by spraying contact cleaner in to the base of the signal stalk and working the dimmer lever. It gets gummed up if it's not used regularly.

I was just wondering what your reason was. I have a bowed exhaust manifold that I bolted on to a head and found that it doesn't take much force at all to bend the manifold down to the mating surface. Probably a millimeter gap closed up. The surfaces may not be parallel but the tension applied by the ends of the manifold are not much different than in the middle. Not extreme, for sure. But that's the advantage of having a collection of parts. Even the defective ones are useful. My theory is that the three bolts in the middle of the exhaust manifold hold it tight to the head and that the ends of the aluminum head expand away from center farther than the steel manifold. Aluminum has a higher coefficient of thermal expansion than steel. In other words, if they start out in the same spot cold, the aluminum will grow more than the steel when hot. The hot-cold cycles bend the stud back and forth farther on the ends. That's my thinking anyway. Really, the 10.9 grade might have similar fatigue strength to a grade 7 or grade 8. It's a property that's not considered much. How do you know the Nissan studs are grade 7? I'm no bolt-stud expert, but that's an odd number. 2, 5, and 8 seem to be the common ones, American. 10.9 is a metric standard. And seems to be identical to Grade 8, property-wise. So we've probably been talking in circles.. http://www.tessco.com/yts/customerservice/techsupport/whitepapers/pdf/bolt_grade.pdf That's the beauty of the forums - you have to go learn some new stuff just to keep up. Here's an interesting book on fasteners that I browse through when things start to fade. Carroll Smith's Nuts, Bolts, Fasteners and Plumbing Handbook (Motorbooks Workshop): Carroll Smith: 9780879384067: Amazon.com: Books Might be cheaper here but it looks like his web site is screwed up. It's missing. www.CarrollSmith.com -- Purchasing

I see that you're using a "straight-shot" modified fuel rail. It's possible that you might have fuel pressure pulsing issues, or pressure degradation at the last few injectors. I think that's why Nissan fed the injectors from both sides and installed a damper in the back. I've read that the large volume of more modern rails helps counteract those problems. It will be interesting to see if you have heat soak problems with the smaller rail volume, but with headers. Hope you don't but the set of parts is interesting since nobody has that combination. p.s. I assume that you found one more injector to go with the eBay set?

It's not a tension problem. The threads would probably pull out of the head before the stud failed from tension. But it sounds like you've made up your mind. Probably not a big deal either way. Why are you following Nissan on the nuts, but not on their stud grade? Don't you want to use lock washers and threadlocking compound? Just curious about the logic path.

You can get Nissan factory-quality manifold studs from the dealer. Designed for the application. High numbers in a bolt or stud grade doesn't mean that they're better. Just that they're different. You don't need super-high yield or ultimate tensile strength, you need fatigue and heat resistance. Constant bending and heat-cycling is what breaks the studs. Better to get a stud that's been tested for the application by the factory. You can get the part numbers here, and your dealer will have them. If you get a good parts guy he can find them on his own by car model. They're common and cheap. Datsun 280Z Cylinder Head, Rocker Cover & Thermostat L28E You can get the nuts also. Notice that there are no lock washers. Datsun 280Z Manifold, Egr. L28E (From Aug.-'76)

You might measure combustion chamber volume to see what your CR will be. You might find the flat-top L28 puts you at 12:1 or something.

Continuity is used to check if two points are connected. It does not tell you if there is power. The distributor and ignition module are involved in the injectors' opening and closing. The ECU is connected to the coil via a blue wire to the negative terminal of the coil. This wire also connects to the ignition module. The ECU opens the injectors every three sparks. The ECU also needs to have the tachometer connected to work correctly. I believe that it may be part of a pull-up resistor circuit, but that doesn't really matter. Make sure that the blue wire from the coil negative has continuity to Pin #1 of the ECU at the connector, and that it is connected to the ignition module, and that the tachometer is connected properly. The fact that the engine ran for a little while implies that you have power to the fuel pump. You can check that by removing the small wire from the starter solenoid and turning the key to Start. The engine won't turn over but the fuel pump should run.

You're right, there is a lot of stuff out there, and it's hard to tell what's right and what's wrong. I gave up and just installed the GM HEI external coil to match the module. I think it ohms out at 0.7. I figured I couldn't go wrong with the original GM specs., used on cars like the Camaro with a V8. You know those will see some high RPM. I think that the Pertronix HEI module (there are other brands also like Accel) just has a higher current limit. With a low ohm coil, the heat dissipation is probably the key ot making it last. The new module in the old box in the cabin is certainly cooler than sitting in the engine bay or under a GM distributor cap though. Shouldn't be a problem, I'd think. Plus you can reach over and touch it while driving, and turn on the AC to keep it safe. Here are some of the other brands. Still popular. http://www.summitracing.com/search/department/ignitions-electrical/part-type/ignition-modules/distributor-type/hei

I don't think that the BIP373 has "dwell" control, or the current-limiting function that the HEI module does (and the 280Z and ZX modules). That is one of the things that makes the GM HEI module so useful, it won't allow the system to overheat from too much current. The BIP373 is used with ECU dwell control, I believe, and would probably burn up itself if used. If it triggered from the VR distributor. Not really sure that it would work. Are you using one? How does it control dwell? I think that you could use the BIP373 in place of the ignitor on the 280ZX ignition systems though. People use the HEI module to replace the ignitor, but the BIP3737 seems like it would do the job, for cheaper and in a smaller package. Might have problems with the engine heat though if it was installed in the same spot. Here's something interesting on the GM HEI modules - it looks like Bosch licensed the technology from GM or vice-versa for a few years and several of the outside-the-US manufacturers used the design, in different form factors. The very last one on this page looks like it is the same as the 4-pin HEI module but the pins seem more convenient. I think I've seen the same on a BMW model out there somewhere. Bosch Ignition Modules Edit - BUT, I just found it on Rockauto and it costs $204. So the more compact form comes with a cost.

If you read a few more threads on "running rich" you'll see it recommended often, to measure resistance of the coolant sensor circuit at the ECU. There are several connections along the way that can add resistance. What the ECU sees is what matters. Download the Electronic Fuel Injection Guide from the first link below. Get a meter, even a simple one will do. Try to find a way to measure fuel pressure. Read the Engine Fuel chapter, especially the first few page, if you want to understand how all of the parts work together. You'll waste a lot of money if you just guess and replace parts. XenonS130 - S130 Reference Amazon.com: multimeter XenonS30 Index of /FSM/280z