Breaker Points Ignition Wiring Question

[Love 70 Chevys]

My truck is not ready for the road yet, but I am temporarily creating my own wiring for the ignition and charging of my truck so I can do some good solid "yard driving". It is a 1970 250 with everything stock. I found a great video online with this schematic. My only point of confusion is the resistor. Would my truck have had this? I know sometimes there is a resistor wire involved, but since I am creating my own, this would not be there. Any advice would be much appreciated!

[Steeveedee]

The resistance on a GM vehicle of that era was provided by a wire in the harness. I think it was nichrome, but everyone called it the "iron wire". It is braided. If you look at the coil power wires, you will see two on the + side. The yellow one feeds power from the solenoid "R" terminal while cranking. The other wire comes from the ignition switch when it is in the "on" position. Follow it from the coil back in the harness. If you turn the ignition switch to "on", you can check for voltage on that wire. If that wire has been removed, you will have to provide a resistor. You can also buy the resistor wire at the parts store, if you have no intention of switching to an HEI in the future. Here is the engine compartment wiring schematic for your reading pleasure.

[Love 70 Chevys]

Thank you for the info and the schematic! It really helped in my journey of learning. I did find the resistance wire in what is left of my original harnessing. Found the length that goes from the firewall pass through to the coil, but nothing inside the cab that went to the ignition switch. Anyway, for my yard driving, I am not going to use any of the original wiring or the ignition switch. (Worried I might burn the truck down!) It sat for many years. I am going to buy a new universal ignition switch just to use temporarily. I have a whole new wiring kit for the truck, but don't want to put any of it in yet as I will just have to take it back out. I will go the ballast resistor route for now even though the truck did not come that way. From what I researched it looks like a 1.8 ohm resistor will do the trick, and as a check I should get about 9V at the coil while running instead of 12. Sound about right?

[geezer#99]

For what it costs for a resistor and switch you could buy a cheap hei and use a push button to start it.

[gmc684x4]

Worried about worn out stock wiring why not buy a new engine harness section made by M&h or Aaw
Gmc pauls lmc brothers ebay are a few places you can guy it from

You can replace as little or the complete harness this way they make them like the originals or upgraded to hei and si altenator eiting upgrades built in

[LockDoc]

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To answer your question, yes, you will need the resistor or you will burn the points up. You should be able to get one at any auto parts store. It is called a "ballast resistor".

LockDoc

[RichardJ]

>>Found the length that goes from the firewall pass through to the coil, but nothing inside the cab that went to the ignition switch.<<

Yes, maybe, depending on that you mean by "nothing" ?

The 20/W/OR/PPL cloth covered resistance wire, mates to the 12P standard copper wire on the under dash harness that goes to the Ign Switch and to the fuse panel.

What do you mean by " my yard driving " ?

If are just moving it in or out of the garage while you're working on it, just "Hot Wire" it.

For a few minutes run time you don't need the resister. Damage to the points will be minimal.
A length of wire from the Battery to the coil "+" terminal and a long screwdriver to short the solenoid "S" terminal nut to the Bat cable nut is all you need.

No harness or switch needed.