I've been reading about 6v to 12v conversions for my '53 Pontiac flat six and I understand the headlights, starter, charging system part fairly well. I'm planning on using a 12v coil, however I'm not sure if I need a ballast resistor between the coil and the distributor.I have new points, a new condensor as well as a new cap and rotor, I'd hate to fry all these parts because I didn't drop the voltage between the 12v coil and my stock distributor.
Even if I'm using a 12 volt coil? Doesn't the resistor lower the voltage? I only ask because I have a few 12 volt coils to use and don't want to buy a coil if my engine turns out to be junk. (It hasn't been fired in 40 years) Will the points and condensor handle 12 volts?
Depends on the coil you use. Some have an internal resistor (It will be marked if it does). If the coil uses an external resistor, it should only have about 7V going to it. A standard 1 1/2 Ohm resistor will do the job, otherwise, you'll blow up the coil if you run it on 12V continously.
You need to have approx 3 ohms resistance before the points. Some coils have this built in just the coil ( example is the bosch blue coil) and others are 1.2-1.5 ohm. Most systems use a 1.2-1.5 ohm resistor and a 1.2-1.5 ohm coil for points.
I just coverted my '48 ford truck. I didnt put one in mine but you guys have got me thinking now. I've only driven it about 5 miles since.
The ballast resistor is used so that when starting a full 12 volts can be supplied to the coil by bypassing the resistor supplying a hotter spark for starting. Both GM and Ford to this with a wire from the starter solenoid to the + side of the coil. A constant 12 volts will eventually fry the coil and/or the points.
Thanks for all the replies. This is the coil I have: I looked it up on summit and it says I need a .85 ohm ballast resistor to use it in conjunction with the factory resistor (which I don't have) Will I need another resistor besides a .85 ohm if I use this with my stock 6v distributor? I'm terrible with electronics!!!
Yeah, it says you'll need the special .85 ohm resistor and the original resistor (which could be a universal ballast resistor, such as the one a parts store would sell to replace the original resistor on a 1956 Chevy for example) You would connect the two resistors in series.... ignition switch to first resistor, first resistor to second resistor, second resistor to + terminal on coil.
Thank you for all your help. I'll be buying resistors after work tomorrow and if the rain holds I'm gonna see if the old flat head will start!
I checked my Bosch blue coils last night and confirmed what Bubba had said. They each had 3.8 ohms across the coil. I am going to go around my resistors.
No need to worry about the condenser, it is simply a capacitor. It works on the same principle with 6V or 12V.
Thanks for all the help. I was going to see if the engine would start this weekend and when I cranked the engine over I noticed I had no spark. Then I remembered the previous owner said he had the engine rebuilt so I started looking at the distributor... I pulled it out and saw light through the block! Looks like the oil pump is not in the block (it's externally attatched) so I have to locate and install one before I can try this again. I also need the transmission input bearing retainer (guides the throwout bearing) for the 3 speed transmission if anyone has one! Needless to say, I'm bummed this weekend.
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