Yep, my comments were not directed at you. However, if you had two modules fail in short succession, it's a good idea to check the other things that the helpful commenters mentioned rather than just ***uming a bad part (which we know there are a lot of). The frustration of having another one fail will come with a lot of "should have checked that" hindsight.
@Moriarity , that’s why I mentioned what Jim did when he converted my friends Stude. Looking closely you could see the loom I used to route it, but with the hood open, you’d have to have prying eyes to notice it. I agree on the visual aspect of them. All GM had to do was do as they did before and after, run a remote/separate coil, not cludge the cap up with it.
HEI module failure is usually caused by an issue down stream from the module and often as not by the coil. Every one that I had a module go out on had an issue with the coil or other secondary ignition parts. Coating the back side of the module with dielectric grease is an absolute must for them to live. The Napa Echlin Or real AC Delco modules still are reliable. I saved the Napa test bulletin on my photobucket pages years ago and it will walk you through testing all of an HEI except the module and that takes a special tester. https://photobucket.com/u/mr48chev/a/0f0967c7-ef41-470d-8118-34b5e1631d08
Those Chinese parts will and have gotten people killed. Guy I knew pulled out onto a busy two lane road, module quit and a tractor trailer ran over them. Killed his girlfriend and he has severe brain damage. Investigation revealed a faulty HEI module. Aftermarket. I run a Unilite. Used them when I was a kid. Never had a problem. Look decent too.
Given that I drive mine nearly everyday, I wanted something reliable so I decided to run a small cap HEI from DUI with their Inferno 1 can coil. Looks decent and just clears the firewall. It's only been a year but so far so good. It's getting new wires soon too... An alternate to the ugly *** stock HEI and it isn't made in China.
I built a small block mopar distributor for an 8ba, with the sole purpose to try electronic ignition. I am hiding the triggering module in a voltage regulator box(crusty). Haven't fired it yet, if plan goes to ****, I have a Bubba's GM points conversion on deck.
A bad plug wire, plug wire that comes loose at one end and such problems does indeed lead to a situation when the spark doesn't have anywhere to go, or if it does it has to jump much further than normal to get there. Both scenarios means the secondary voltage goes way, way higher than normal, and that in turn means the primary voltage goes up very high too. The primary voltage naturally goes straight to the switching transistor in the electronic module, and while it will be able to handle many hundred volts there IS a point when it will break. There's probably some protective components in there too in a good brand module giving the transistor a chance to survive a bad ignition wire, but don't be surprised if someone didn't see a need to put any overvoltage protection in a cheap copy... The electronic ignitions generally provide a far stronger spark than points ignitions. The upside of that is that the engine may keep running fine even with problems like a bad ignition wire - the spark just has to jump past the break in the wire to get to the spark plug. The downside is that you may not notice having a bad wire and keep driving with it until something else (i.e. the module for example) breaks as a result of the abnormally high primary voltage. A weaker points ignition would probably have misfired due to being too weak to provide good spark, warning you there was a problem. You always want to take a close look at why something broke, many times it's a symptom of another problem. Unfortunately it's hard to quickly and easily get a good idea about how all the ignition parts work without an oscilloscope. On the other hand, with a scope many issues can be identified in seconds. One cylinder consistently having significantly higher spark voltage than all the others would be like a bright neon sign pointing towards a problem that needs to be investigated.
@big duece , I see you used the heat sink from the 7 pin modules-mid 90's, in your application. I just grabbed another one the other day, for my next conversion. Fits the 4 pin module by cutting a fin or 2 off.
Make sure you have the proper size wire going into the cap , GM cars had 12 ga. wire for the battery feed. Just a thought. As already mentioned most failures back decades ago when I did this every day where caused by a miss . Usually burning a hole in the rotor. So maybe undersized wiring could cause a issue as well.
My self , I have worked in Fleet many Gm & still to this day use & have many 1st gen HEI , in all the years since late 70s , I have only replaced 3 modules maybe 4 , In my opinion Gm module pretty reliable
The Jalopy Journal
