How do I tell the difference between the electronic ignition coil and the one meant for points? I just bought a '79 620 with an electronic ignition distributor but the coil was missing. I want to put it in my other truck which is a '74 body with a '74 wiring harness and a '78 L20 motor and I don't want to wire it up wrong and burn up the box on the side of the distributor. (my dad has done it once!) Can I wire up the EI distributor and coil with my '74 wiring harness? I've read where this question has been asked before but I thought maybe my setup is different any help wouldbe greatly appreciated.  

This is the dist. & EI coil i pulled & am now running on my 74 620...
[IMG]http://img.photobucket.com/albums/v605/ ... 6_ORIG.jpg[/IMG]
in text on the bottom it says for use w/ EI...not all may say that but mine did. Also the EI coil is taller & wider & thats another way to tell.

what about wiring it up? The wires on a '79 going to the coil are BW and L (black and white & Blue). My '74  wires are black and white & black and red. Do you have any pics of your distributor and coil installed?

Just make sure that the wires go to the correct sides of the coil. Meaning whatever wire is + make sure it goes to the + on the new coil. Ive swapped over to EI using the 610 dist. & a GM HEI module so the wiring is a little diferent. Heres a writeup.....


> Wiring for the HEI unit.
>
> W - Connects to the positive lead at the distributor.
> G - Connects to the negative lead at the distributor.
> C - Connects to the negative side of the coil.
> B - Connects to the positive side of the coil.
>
>
> Okay...I'll add this to it........
>
> You will need a new wire from the RED wire on the dist to the W on the HEI
> unit.
> You will need a new wire from the GREEN wire on the dist to the G on the
> HEI unit
> These two wires are what "senses" the tiny voltage spike that will be sent
> from the pickup in the dist.
>
> You will need a new wire from the (+) of the coil to the B on the HEI
> unit. This provides the power to the HEI unit. It's electronics needs to
> get power from somewhere. You will "add" this wire to the existing wires
> on that terminal of the coil. You will have wires on there from the
> ballast resistor, the "start/crank"(full 12v) wire from the ign switch. Do
> not remove the ballast resistor unless you have a coil that is rated for a
> constant 12v. If you remove the ballast, you can simply connect the two
> wires from the resistor together. You may have only one wire at each end
> of the resistor and then you have a 2nd wire on the (+) term of the coil.
> The second wire is the "start/crank" wire from the ign switch. You should
> be able to see which wire runs from the resistor to the coil. If not, the
> black/white is from the resistor and the red is from the ign sw. If you
> simply take the resistor out without connecting to the two wires together,
> your engine will only fire when the key is in the crank position and will
> die when you quit cranking. If you remove the "start/crank" wire, you
> will still get volts to the coil through the resistor in the crank
> position(I double checked that on the '74 620 w/man trans wiring), but the
> starter pulls a lot of amps and you may not get enough power to the coil
> to get a good enough spark to start the eng.
>
> The wire from the (-) term of the coil can be the old one running to the
> dist, but I'd just run new and disconnect the old one. You may have two
> wires on that term...one will be the tach if you have one. This wire runs
> to the C on the HEI unit and turns the coil on and off like the points
> did.
>
> The HEI unit grounds itself through the metal plate on it's backside and
> the collets in the mounting screw holes. You want to make sure you mount
> the unit to a piece of aluminum with a small amount of heat sink compound
> for heat transfer. Then mount the alum bracket to a good chassis ground.
> I would try to tuck it up, more out of the way so that water and debris
> flying up don't hit it. It was designed to be inside the GM distributor.
this is the HEI i went with... http://www.partsamerica.com/ProductD...pe=194&ptset=A

This is how I have it hooked up but it still doesn't run. I have fire at the plugs though. 



 

I have the ignition module on the side of the dist., is this what you're calling a hei unit? I only have the coil with the ballast that was running the dual point dist. I had on there.

ok I have it running but it hits a flat spot about mid throttle and if I hold it there it cuts off. And it backfires alot! I mean literally there is fire coming out of the tailpipe. I'm almost ready to buy another gasket and bearing kit and build another motor.