Purchased and installed hei dist for my 71cs, watched about 10 YouTube on how to wire it, they all said run a wire from fuse box to batt terminal on dist. Can someone explain why I can't take ignition wire from the now unnecessary coil into the new dist?

 

That is a resistor wire and has low voltage. HEI needs as close to 12 volts to function properly.

 

Because it is a resistance wire for points, I believe. You can trigger a standard 5 pin relay with it fed from the battery. Alternatively, you want a 12ga minimum wire tied to the ignition circuit/pink at the ignition switch.

 

Don't forget HEIs have a different timing curve, so if you go with the factory initial timing, your engine will be a dog.

 

I was considering this as I just put an HEI in. I was not sure if the low voltage would trigger relay plus I became lazy and ran wire to fuse box and found a spot that turns on with key and called it good. But I like the relay idea and may change to it.

 

Makes sense, thank you

 

If the load doesn't necessitate a relay, wouldn't adding one put an additional potential failure point in the circuit?
Also the relay would be supplied that same reduced voltage.

My $0.02

 

Any connection through the firewall should be fused, so I would at least put a 20a fuse in line at the ignition switch. The HEI coils like a lot of juice, which a relay would provide. Plus, you don't have to go through the firewall. There's a bunch of ways to skin that cat.

 

Yes, but many relays work correctly over a range of voltages. So use a relay that will operate down to 5 or 6 Volts.

 

The relay avoids adding load to the interior wiring circuits--in our old cars, that load can be heavy on those corroded connectors. And that can mean you might not get full voltage from that source.

The relay would use the original ignition (resistance) wire to supply its pull-in coil--the power draw of the pull-in coil is so minuscule that there would be virtually zero voltage drop in the ignition wire supplying it.

The relay would switch battery voltage directly to the HEI, bypassing the voltage drops in the interior wiring circuits.

 

Relay makes sense then...thanks for educating me...

 

After you get the wiring sorted out, do the ignition curve, All 3 timing events...base, vac, and centrifugal need to be customized to your application, fuel, elevation, and driving habits.
These 3 timing events need to be dialed in along with the air-fuel adjustments. All of this needs to harmonize to yield the best results.

The starting point for an average Oldsmobile with street manners:
1. Base 12-14° (vac canister isolated).
2 Vacuum, another 8-10° @ 750rpm hot curb idle. (now you should be at 20-22° at idle) . Use an adjustable stop vacuum can not an adjustable-rate canister.
3. Total timing all in at ~2800-3000 rpm for a grand total of 36-38-40°
4. using a vacuum gauge adjust the A/F screws to obtain the highest possible vacuum reading. Twist the distributer to get the highest reading. Go back in forth between timing A/F to achieve the highest reading at idle. This is super tuning. Road test and repeat. Spark knock means one of the 3 events needs to be reduced. Heat soak will be your enemy. That's another convo.

 

Excellant explanation. Can't go wrong with this set up.

 

Ouch! Will keep that in mind as I save my pennies for either a carb or F I system, thanx for the info