Fitting a HEI Module in Transistor Ignition Unit 1977 280Z

[EuroDat]

I posted this in someone elses thread, but decided to start a new one here. It may be useful for other members having problems with the TIU. These systems are getting old and starting to fail more often than not.

A couple of months ago I had problems with water in the fuel system. After cleaning it all out, draining the tank replacing the fuel filter the engine ran normal again. When I took it for a drive I was lucky to limp back home with the engine coughing and backfiring. Went through the EFI bible test and found some poor soldering joints on the aftermarket injector connectors and some minor things. It still would not run right once it warmed up. It was great cold, but once it warmed up bang it started all over again. The tacho was bouncing a little, but it didn't seem enough to be the ignition module and it checked out ok. I thought the tacho bounce was due to the lurching forward and stalling of the engine.

To eliminate the ignition I changed to a HEI Module (a cheap $10.00 unit to test with) and the engine has ran perfectly ever since. The ignition unit played up fierce when it was hot, but its been running perfect for the last two months.

Here are some photo's of the temporary fix to see if it was the TIU.

This is the unit I used to do the testing and if all goes well I plan to upgrade to Flame Thrower.

Now its up and running my next step will be to install the HEI Module in the old TIU casing.

Chas

[EuroDat]

I made a simple wiring diagram of the setup Im now building. Its a little different around the resistor.

Im using a 12V coil and bypassing the resistor. The wire from the ignition switch is connected, but doesn't have any purpose atm.

Thanks to Wayne (wal280Z) for the awsome effort he has done with the color wiring diagram.

Some photo's of the work in progress.

Chas

[SteveJ]

Did you use a conductive material between the HEI and metal plate to act as a heat sink?

[EuroDat]

Did you use a conductive material between the HEI and metal plate to act as a heat sink?

Yes, I used a white heat tranfer paste we use at work for pt100's in thermowells etc. If you look closly at the photo under the wiring dagram, you can see a white smear after wiping away the excess paste.

Edited July 8, 2014 by EuroDat

[Captain Obvious]

That's a really neat idea.

[SteveJ]

I like the looks of it. It certainly eliminates the look of a kludge factor.

[zKars]

This a very good idea and method of execution is very clean. Well done. Nothing beats a modern ignitor to replace 40 year old crap. It is little surprise that your car runs better than it did before.

I feel compelled however to lend some advice. The generic cheap GM HEI ignition module is not the best component for this purpose. There is/was a lengthy (older) thread on hybridz about ignition instability at higher RPM's with some of the more bargain basement varieties of thes items. At the time, there weren't a lot of options, though MSD and others had "high performance" versions of the basic HEI module that performed better. jegs or summitracing.com probably sell several varieties. I'll try to find the hybridz thread and you can decide if its helpful.

Good news is that there are more modern and well tested components. DIY autotune has one of the better ones, the BIP373 is the one that comes to mind.

DIYPNP BIP373 Ignition Module and Heatsink Kit DIYAutoTune.com

This thing can replace the HEI module, or the E12-80/92 module on a ZX dizzy or any reluctor based distributor and will fire any basic 12v coil. And its smaller. And at $9.80, I buy three to carrytwo as spares, JIC....

[Zed Head]

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.

Edited July 8, 2014 by Zed Head

[EuroDat]

I have done a little research on the HEI Modules too. Not to say Im any kind of expert, far from it. More like enough knowledge to be a little dangerousLOL

The Mopar guys seem to be very fond of the HEI module and there is plenty of good and bad information on their forums.

What I have found on the net and through talking to a Buik guy in the street behind us. The GM HEI is considered one of the better modules, but it is also a lazy module and can run with a higher ohm coil, it just won’t go to current limiting control. To get the best out of a HEI Module you should use a 0.5 or lower ohm coil. That way the module will use its current limiting abilities and produce the best spark.

Here is a good example of what a low and high ohm coil will do to the HEI's performance.

I think this could be some of the problems people are having with poor performance and not revving past 5000rpm.

If my mod goes well I am planning to use the Pertronix Flame thrower HEI and (stock looking canistor) Coil.

With a bit of luck Ill have the mod done tonight and test drive tomorrow.

Chas

Edited July 8, 2014 by EuroDat

[Zed Head]

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

Edited July 8, 2014 by Zed Head

[EuroDat]

Hi Zed, I was thinking along those lines as well. Cooling should not be a problem in the car.

For now Im running the el cheapo and I have a spare. The coil is a 40kv with 0.6ohm. It was the closest I could get without special ordering. Good enough for R&D and normal driving.

The link you posted has some good alternatives. I was looking at the Accel 35361 and the Flame thrower.

Chas

[EuroDat]

Well the TIU in back in and the engine is running fine again.

I had one little glitch. Managed to get the reluctor wires mixed up and the engine would not rev past 2500 rpm. I remember reading about this somewhere and after checking found the green and the red wires on the wrong terminals. One of those Homer Simson "doh" moments:stupid:

Next step is a small strip across the resistor so it looks stock, but the resistor then has no function.

Ill post some photo's later.

Chas