Interesting 8 pin HEI issue

-
7dart0

7dart0

Well-Known Member
Joined
Apr 20, 2012
Messages
491
Reaction score
104
Location
peabody,ma
First off I had a bad ignition switch and fried the hei (don't ask lol). I replaced the module,and he car is running great. I'm currently getting ready to add a procharger so I have an FBO limiter plate that I'm using to lockout timing.
Well with the distributor locked and vacuum advance plugged at about 4k rpm its advancing about 6*. What the hell is up with that? Is it a bad module from the parts store or is there advancement built into these things?

Tom
 
If my GM memory serves me correct the 8 pin has that technology.
The 4 pin (what I run) does not.
 
Something in the back of the old man's mind I don't remember. Do a Google. Maybe you must ground the advance control terminal I don't recall. As above, "for now" I just run the 4 pin version.
 
I might switch to the 4 pin anyway so I can buy an aftermarket one with a rev limiter.
 
If I change to the 4 pin module can I use the coil I'm using with my 8 pin hei module?
 
Yep In fact "as an experiment" I used the same old Mopar coil on mine that was on the car. Ran it two summers. Even without a "special" coil the HEI produces more spark than the factory points/ ECU
 
67Dart273 said:
Yep In fact "as an experiment" I used the same old Mopar coil on mine that was on the car. Ran it two summers. Even without a "special" coil the HEI produces more spark than the factory points/ ECU
Click to expand...
I am running a HEI . It was only in the car for a few hrs and it shut down like I shut the key off . Checked for spark . It was dead . Met alternator is putting out 14.9 volts . I’m wondering if it is too much for the modul.
 
Don't know.......only relating my experience..........how did you heat sink the module? 15V is a bit high but not THAT bad. You need to look into that. It's typically voltage drop to the VR which causes over-voltage
 
67Dart273 said:
Don't know.......only relating my experience..........how did you heat sink the module? 15V is a bit high but not THAT bad. You need to look into that. It's typically voltage drop to the VR which causes over-voltage
Click to expand...
I didn’t change the modual . It is a new distributor . What do you think about using a ballast resistor with the HEI ? And I converted to an internal voltage regulator .
 
on the 5 pin (1980 Oldsmobile Toronado V8) the 5th pin gounded retards 5 degrees for starter (and can be used for a boost retard by wiring in a Hobbs NO pressure switch)
FXK88MRHO237K2E.jpg
 
Last edited:
7dart0 said:
First off I had a bad ignition switch and fried the hei (don't ask lol). I replaced the module,and he car is running great. I'm currently getting ready to add a procharger so I have an FBO limiter plate that I'm using to lockout timing.
Well with the distributor locked and vacuum advance plugged at about 4k rpm its advancing about 6*. What the hell is up with that? Is it a bad module from the parts store or is there advancement built into these things?

Tom
Click to expand...
How would a bad ignition switch destroy your modual? It would either supply power on not .
 
start and run could have bucked voltage if it were not wired correctly....? What made you pick the 7/8 pin, thats overkill for a locked out distributor,
 
Do not run a ballast res with HEI. HEI has an internal current limiting cct to limit coil current. Adding a resistor would further reduce current & give a weak spark....or maybe no spark at all.
 
Ahh, the good old 8 pin. I found this out the hard way. I read up on the GM HEI module swap and decided i wanted to try it out, so i went to the junkyard and got the 8 pin module and coil and gutted my old mopar ECU and put the 8 pin module inside, got it going and kpt getting ping at WOT and couldnt figure it out, so i hooked up my timing light and watched..with the 8 pin module, it would advance the distributor an additional 10 degrees of what i had the mechanical at! Long story short, i ended up having to go to the 4 pin module to stop the extra advance. I did keep the coil that is found on the same vehicles that have the 8 pin module, so it works just fine with the 4 pin.
 
The megasquirt site has much info on various GM HEI modules, Ford TFI, and such.
 
You must log in or register to reply here.
-

Back
Top