GM 8 pin HEI Conversion pics

waid302 said

Hello TrailBeast,

I am a new member

I am here and very interested in this 8-Pin HEI module setup. GM introducted the 8-pin HEI in 1988 - full 14 years after the 4-pin HEI came out back in 1974 so its safe to assume its "better" than the 4-Pin HEI.

At one time I had a 77 Olds Omega (Chevy Nova) and was going to convert to TBI. I don't the Omega anymore but still have 3 original GM 8-Pin modules and a HEI Coil. I recently bought a 64 Ford Falcon and doing a 5.0 swap with Duraspark Distributor & HEI Ignition Module. The Duraspark Ignition Box also has a bad reputation. A lot Ford guys & others always seems to use the 4-Pin HEI module. Very little information is available on the 8-Pin HEI with carb setup.

Do you still have mechanical advance with 8-Pin HEI ?

Have you observed any timing retard (which I believe only work with ECM) during start with 8-Pin HEI ?

Thank you,

Waid

Click to expand...

Hello Waid,
Bill pretty much covered it (Thanks Bill)
I would add that the megasquirt EFI systems also use the 8 pin module for timing control.
My setups don't use the timing functions of the 8 pin unit, only the ECU for the ignition, but I use them because they are used by Holley and Megasquirt and they are more tolerant of low voltage than the 4 pin.

So, yes you still use mechanical and vac advance with them as there is no computer to control them with unless you buy or build one.

There is no timing retard unless .5 volts is applied to the "D" (white wire) on the four pin weatherpack connector.
With that .5 volts applied the ECU will go into "Limp Mode" retarding the voltage 10 degrees.
This function may or may not be applicable to boosted (turbo) systems, but I have not verified how much retard is needed for certain amounts of boost, or if the .5 volts is just on or off and not variable.
I would think it's on or off only, but I have not tested that theory yet.