77 280z Restoration

[Zed Head]

There is a ton out there on the old internet about the mounting flange being a ground circuit.  Guys have disassembled them, examined the circuits, drawn them out, and explained them.  The sheer mass suggests that it is correct, but I can't find an official GM document.  An electronics guy with a meter, and maybe a battery, could probably confirm it.

I did find one thing that I had forgotten about - the two plastic locating pins on the bottom of the module.  You need to cut those off so it lays flat, so that you get good conduction in to the heat sink.  A pair of wire cutters works, the plastic is not too hard.

I mounted mine across from the exhaust manifold on the fenderwell because there was a nice threaded hole there.  Can't remember what it was for originally.  So I built a small heat shield that I hung (hanged?) from the intake manifold.  Just being careful...

[Av8ferg]

Thanks for Info Gents.   I built my prototype for a new mounting location for the E12-80 module.  I’ve mounted a bracket to base where the AFM rests.   Might need to make some changes depending on clearance issues once all wired up but I think this might work as is.    Like I said earlier I’ll mount the HEI to the existing bracket where the old TIU came  in.  It has a small bracket there and it has two screw holes to work with.  

[EuroDat]

On 9/3/2022 at 10:00 PM, Av8ferg said:

Thanks Steve, so more likely to burn up a module with a low primary resistance coil.   Safer using a 1.5 coil over a lower one.  
The spark to the plugs would technically be lower too on a 1.5 ohm coil vs a .6 ohm coil.  

Just for the info. I'm on holiday in france and not online much atm.

The GM HEI 4-Pin have current limiting abilities. It is designed for a 0.6ohm 12volt coil, but will run fine up to 1.5ohm. Any higher ohm rating will risk open circuiting the hei module.

I used my HEI module for 5 years without every having any issues with it. My original module would give up when it was hot. Had to spray itwith circuit cleaner to cool it and it would run for another ten minutes.

Location of your module looks good. Best to get as far away from external heat sources.

Edited September 6, 2022 by EuroDat

[Av8ferg]

Thank Chaz.  
Here’s the update.  I’ve mounted and wired up the E12-80 module as depicted above.   Temporarily wired it to the distributor just to test and the car started right up and ran fine.   With this new location I was able to test my other modules some Nissan some aftermarket.  It took no more than 1 min to conduct the swaps.   I received the HEI but still waiting on the heat sink to arrive, should be her tomorrow.  
I took some temperature samples after letting the engine get to operating temperature.  The base of the distributor was around 150 deg F and the module located next to the AFM was running about 120 deg F.  Touching it  felt pretty hot to the hand.   I’d like to see it run cooler, if possible.  I guess I could get crazy and mount a mini fan that is used to cool computer processors, would be easy to do but probably not required and a total over kill.   
I wanted to go back and discuss my thermostat findings.   I ordered two extra thermostats and after removing my old one I tested all three in a pan of water on the stove.  
There brands were Stant (old one I removed from ca4), Gates (premium grade) and MotoRad (high flow).  After the tests they all opened per the FSM  and at 189F we’re full open (these were all 180f spec) .  I’ll put pics below of each,   The MotoRad look the best made, because it had a more robust construction but it  also had a 5mm wider opening at full operating temp than the other two.   The Stant and Gates look identical.   
Here it is on Rock Auto where I bought it.  Car temp gauge seems to go to about the F in the middle of the temp gauge now.  Before it would go past a bit. 
https://www.rockauto.com/en/moreinfo.php?pk=4483860&cc=1209248&pt=2200&jsn=10415

[280Zrewind]

Just for my info - I saw in previous posts that the ZX ignition was an improvement over the Z.   What did they do to upgrade?  I may be interested in the upgrade for my project down the road.  

 

[SteveJ]

47 minutes ago, 280Zrewind said:

Just for my info - I saw in previous posts that the ZX ignition was an improvement over the Z.   What did they do to upgrade?  I may be interested in the upgrade for my project down the road.  

 

The ZX went from a box bolted to the passenger side firewall (Transistor Ignition Unit or TIU) down to a small module on the side of the distributor. 

If your distributor and TIU are in good shape, you won't see any performance difference. Also, ZX distributors are getting rare. If the TIU dies, look into converting to an HEI with your existing distributor. I believe @EuroDat did a nice write up on doing that many years ago.

[EuroDat]

16 hours ago, SteveJ said:

The ZX went from a box bolted to the passenger side firewall (Transistor Ignition Unit or TIU) down to a small module on the side of the distributor. 

If your distributor and TIU are in good shape, you won't see any performance difference. Also, ZX distributors are getting rare. If the TIU dies, look into converting to an HEI with your existing distributor. I believe @EuroDat did a nice write up on doing that many years ago.

I'm not an expert on the issue, but my experience on the ZX distributors is as follows. There are two (three for Fed) "main" design differences in the 280Z and 280ZX distributors.

1. The 280Z Cal and Fed a 6 pronged star wheel would pass a single fixed magnetic sensor and induse a pulse to trigger the TIU. The Fed had dual fixed magnetic sensors. One sensor was retarded 7 degrees and the TIU used it during warm up phase. The magnetic sensor only gets one prong to induse a pulse. This gives a weak signal starting at 0.5 VAC at cranking and reaching somewhere around 8 to 12VAC above 3500rpm. Well 12 VAC was the best I could get out of three units in my dodgy test with a drill in a bench vice.

2. The 280ZX (non turbo) has a fixed magnetic ring with 6 prongs pointing inward and the rotor has a matching 6 pronged star wheel. When the rotor star aligns with the 6 fixed magnetic prongs it generates a magnetic pulse through the spool located under the magnetic ring. The voltage signal activates the TIU. Typical cranking voltage is 1.0 to 1.5 VAC and goes up to around 50volts as rpm increase.

3. Location of the TIU. The 280Z has an external bulky TIU located at the passengers kick panel.

The 280ZX has a compact (matchbox) sized TIU mounted on the side of the distributor. The 280ZX is not the best location for the TIU. Heat is your enemy so lets mount the TIU between the radiator and the nr.1 exhaust manifold☹

Usefull info: If you are looking for parts.

The pickup in the 280Z is the same as the early L20B (75-78) EI distributor.

You can also use the L20B TIU LX507 or LX512, but on the 75 - 77 280Z you will need the TIU connector plug to connect it and replace the coil and ballast with a 12V version. The L20B after 78 had the matchbox TIU like the early 280ZX. It will work on the 280ZX distributor.

Both types of distributor will trigger the GM 4-pin HEI module. The GM HEI requires a minimum of 0.3VAC to activate. Altough the 280Z has a poor (low) voltage pulse during cranking it will still be enough to trigger the HEI.

 

 

Edited September 9, 2022 by EuroDat
Typo

[280Zrewind]

Thank you for the replies!  This could be very useful to me going forward. 

[Zed Head]

One more small fact would be that 1978 got rid of the ballast resistor and opened up the spark plug gap.  Implying that they were using current limiting technology like the GM HEI module.  74-76 used the ballast and the smaller gap.  

1977 is odd though because they kept the ballast resistor but opened up the plug gap for USA models.  Weird, don't understand it.   Might be a typo because in the Engine Electrical chapter they show the big gap for Canada models.  Engine Tuneup shows otherwise.

But 1978 seems clear.

[Captain Obvious]

On 9/9/2022 at 4:17 PM, Zed Head said:

Implying that they were using current limiting technology like the GM HEI module.

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.

[Av8ferg]

I got my HEI installed today and took the car for a drive.  I rode it pretty hard and it was a hot day today.   The car ran flawlessly, clean acceleration and no engine hesitation anywhere.  I only pushed it to 5,000 rpm because my engine is still very new., but it was perfect up there.  Overall I’m happy.  I also have my Nissan E12-92 unit bolted up a few inches away from the HEI and have almost completed the full wiring setup that will allow me to swap modules very easily and rapidly using no tools.  Hey I’m a pilot I like redundant systems.   We have 3 of just about everything on the jet I fly for work. 
Here are some pics, it took some hole drilling to make all this merry up right and some special totally flat pan mounting screws for the heat sink so the module would sit flush, there wasn’t a lot of room in the heat sink so this was a must.  
Once I finish all the wiring clean up, like the setup coming out of the distributor I’ll test the two modules back to back and provide an honest comparison.   I made a plate that mounts to the distributor that attaches using the same bolt holes the original module attached with.  Then I cut out a notch on the top of that plate and set in there one half (male) of the weatherproof wire connector and then using steel stik I formed a perfect mold of the area where the wires exit the distributor and around the connector.  Now it will be sealed and a clean attach point.  I haven’t totally completed that so expect pics of that tomorrow,

[Captain Obvious]

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