Jump to content
HybridZ

4-wire HEI setup problems...sigh


Recommended Posts

Go get a new module, properly ground it through the bolt holes first THEN apply power and start troubleshooting.

 

And consider testing with somthing more advanced than a test light. the 0-5VDC scale is more than resolute enough to verify CAS and ECU input/outputs for the sake of proper triggering at the last link in the chain (the HEI Module)...

Link to comment
Share on other sites

They are a different ground. One is a reference for one circuit, the holes are ground reference for the power transistor and internal circuitry.

 

Without the holes grounded, voltages inside that module go on spiking frenzies, and toast the internal components "toot-sweet"...

 

When I was working at a GM dealership in 79 and 80, the one thing the GMI guy giving the HEI Training stressed was to NEVER power-on an HEI until the module was BOLTED DOWN (with the heat-transfer grease of course!)

 

The other thing that kills them is heat, either from not greasing the base, or insufficient heat sink in aftermarket applications. I have mine on an aluminum plate that is 5X8 and it STILL gets HOT to the touch. You want surface temperature to be below 145-150F if at all possible. Inside the distributor isn't the greatest place to put these things, but I guess the boys from GMI didn't want to copy Chrysler, who bolted their HEI Module to the firewall....a BIIIIIG heat sink!

 

BTW, both the metallic bottom and the metal 'rivets' through those holes are connected, and are all the same common ground plane. It is totally isolated from the circuitry that the "Ground" wire is hooked to...which is part of the reason these things go bad so often...people don't see much about it other than 'bolt it down'---they never get the whole GM explanation of WHY it needs to be securely fastened to the chassis ground. Many times, you can find grounding straps on HEI dizzies that had issue with intermittent spark---someone was under the impression that an aluminum dizzy base bolted into a cast iron block might not be grounded properly (apparently Nissan thinks this as well, as they have a Factory applied ground strap!)... Generally on a Chevy though it was an issue that the HEI was intermittently taking a dump because of heat. Nobody drilled holes in the cap and let the air cleaner pull air thorough the cap to keep cool air circulating... ooops! Someone did!

 

If you are using a four pin HEI (or ANY HEI) and insist on running Autozone or aftermarket crap cheap modules, KEEP A SPARE IN THE GLOVE BOX!

 

I went through three or four HEIs from Autozone before getting one that WORKED RIGHT. That is the one in my glove box as the roadside spare. I put a Per-Tronix Flamethrower on because I didn't like the weak spark of the AZ Crap. It was a whole $40...no big deal there and I have the satisfaction of knowing I have parts that clearly say 'For off Road Use Only, Not Highway Legal' on my streeter! LOL

 

Thing to take away from this is there are TWO ground circuits on a GM 4 Pin HEI. And the one through the BOLTS is the CRITICAL one, if it's not connected...YOU FRY IT!

Link to comment
Share on other sites

Power it on, leave the power on. If it doesn't get hot...it's toast.

 

Another big indication is not being able to get any spark when you gate the appropriate terminals with voltage...like you are mentioning.

 

All it takes is a second ungrounded, and POOF. Go get another one. When I was doing it, there were old-timers complaining because 'points don't take a crap like that!' They were used to being able to leave power on for a while to do testing. I don't know, maybe their brains worked slower. A lot of them didn't comprehend when the Simpson didn't deflect, no matter how you try it...it means there's nothing there!

 

And those Wells Aftermarket Modules are sh*t crap junk. I KNEW what I was doing and STILL three of them fried or were bad right out of the box! The fourth was a heat-soak victim from power on too long in the wrong trigger position. But #5 was the lucky one. And I only paid $13 for it, every one was 'back under warranty' with me griping for the time it was costing me. I actually picked up the one that WORKED on my way to the speed shop to pick up the Per-Tronix Module because I was sick of the cheapo stock replacements. As I understand it some of the performance aftermarket modules use much higher grade components, and are far more tolerant of power on mistakes. But even they will fry without casing ground. It just takes a few seconds longer.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...