What is this ???

[Sweet Shock]

Anyone no what this does ?        Pete

[Sweet Shock]

[matty]

its used to redeuce the voltage on a points ignition system. running 12 volts threw a set
of points would cuse them to burn out in no time at all

[kimbosound]

It is a ballast resistor.......regulates voltage to the coil.....if you are familiar with boch coils.....thaey have a gt40 model and a gt40r......if you have a balast
resistor as pictured adn you change your coil.....use the gt40r

[Sweet Shock]

Ok interesting Can you buy new ones no problem and do they look the same or are they updated, I would asume super cheap would have them, thanx               pete

[Sweet Shock]

I just had a look on ebay Ill be damned, There everywhere, I ve never seen em before

[LS120]

alot of european sports & touring cars used them as the 6-8v coils gave you a bigger better spark.. i used to run a 8v bosh in my old 48 chev pickup with the blue flame 6cyl in it..

and an electronic ing that my dad built & most the time i didnt need to change from 3 to 2 unless it was a steep hill..

David

[BlackBedford]

G'day

There is a very good purpose to the ballast resistor. It makes starting easier.

When the motor is running the battery voltage is about 13 volts, however when the starter motor is winding over the battery voltage will be 10 volts, and that is if the battery is in good condition.
The ignition coil is a voltage multiplier, so if if you drop the input voltage, you also drop the output voltage, which means less spark when you need it most.
By using a ballast resistor, the coil will be operate at its rated voltage when the motor is running.
When starting, the resistor is bypassed and the voltage drop in the battery is compensated so that the coil will still operate at its rated voltage.


Looking at this diagram explains it:



And you always wondered what that extra lead to the stater motor was for, as disconnecting it didn't seem to make much difference.
A good mod for a CF is to put a relay in the start circuit so that the ignition switch is not carrying the load current of the starter motor solenoid. The bypass wire for the ballast resistor should be connected to the output of the relay as well. You will find starting a lot easier if do this.

Note the ballast resistor and the coil are matched to work together so you if you change the coil to a different brand, make sure the ballast resistor is the correct value.
If it is too high you will have poor spark.
If it is too low you will burn out coils quickly.


For more ignition tips go to:
http://www.classictruckshop.com/clubs/earlyburbs/projects/trouble/ignition.htm

I wish I knew about this tip before:

Intermittent Stalling
This problem drives most people crazy. It shuts off when going down the road, then mysteriously starts running again and may run for minutes or hours before the next stallout. My tried and true way to find it is to get 2 test lights. Run wires from the + and - terminals of the coil into the cab. Extend them if necessary. Have a friend hold the lights and then go for a drive. The light on the + side will be steady, and the - side will be dim and/or flickering. This is normal. Have the friend watch the lights like a hawk. When the ignition cuts out, see which light goes out. 
If it's the flickering light (- terminal) Look for shorts in the distributor, bare spots in the wire leading to it, points that are set too far from the cam to open, or a bad condenser. If it has dual points, one set may set so close that they are intermittently not opening.
If the steady light goes out (+ terminal) Look for shorts or opens on the + wire. Typically, the wire leading to the starter melts into the manifold and intermittently shorts, kills the truck, then it moves away again. The ballast resistor may be bad. The firewall connector may be loose. It could also be a bad ignition switch. 
If both lights stay on, or go out at the same time, then the coil has a heat failure problem. Replace it. They heat up, then short internally for a few minutes.


I am adding a bit more. I found the site looking for a picture to explain the ballast resistor. Looking through the site I found a lot more good stuff.
Check it out:
http://www.classictruckshop.com/clubs/earlyburbs/projects/how_to.htm