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Discussion Starter · #1 ·
I have a 66 mustang. I want to put a 302 engine in it. The engine is a 1979 ford truck with (Duraspark 11) distributor. I was told that I need 12 volts to the module at all times and that I should not use a ballast resistor. What happens to the coil if I don’t use a ballast resistor?
 

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I've had a Duraspark conversion for years and years with no ballast resistor. I have an MSD coil and have had no issues.
 

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The Mustang does not use a ballast resistor. Instead, it uses a resistive wire from the ignition switch to the coil. this needs to be rewired with a standard wire. Also, with the Duraspark system, it is just that. A system. You need the "brain" box that runs it. Another option is to use an MSD box to run it too. Keep in mind that if you have a tach, you will also need a signal amplifier from MSD (8920) since the signal is from a magnetic distributor.
 

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yes, good points. here is how I wired mine...
 

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Just some guy
67 coupe, 69 Sportsroof, 86 hatchback
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It's a little different if you are using a stock DII coil. IE, the one from the 1979 pickup. Do this.

Reason being is that a stock coil won't put up with 12 volts all the time in the long run. And yes, I have personally found this to be true. Most aftermarket coils (particularly the "TFI" style ones) handle 12 volts just fine. They also work with the resistor wire like the diagram I'm showing but you'd be giving up a smidge of spark power by doing so.
By TFI I mean one of these. This an MSD version and is what I am currently using.
 

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Discussion Starter · #7 ·
It's a little different if you are using a stock DII coil. IE, the one from the 1979 pickup. Do this.

Reason being is that a stock coil won't put up with 12 volts all the time in the long run. And yes, I have personally found this to be true. Most aftermarket coils (particularly the "TFI" style ones) handle 12 volts just fine. They also work with the resistor wire like the diagram I'm showing but you'd be giving up a smidge of spark power by doing so.
By TFI I mean one of these. This an MSD version and is what I am currently using.
thanks for the diagram. is the pink wire in the original 66 wiring harness?
i bought my car in boxes so i am having to start from scratch. does anything connect to the "s" terminal on the starter relay?
 

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Discussion Starter · #11 ·
The Mustang does not use a ballast resistor. Instead, it uses a resistive wire from the ignition switch to the coil. this needs to be rewired with a standard wire. Also, with the Duraspark system, it is just that. A system. You need the "brain" box that runs it. Another option is to use an MSD box to run it too. Keep in mind that if you have a tach, you will also need a signal amplifier from MSD (8920) since the signal is from a magnetic distributor.
Thanks for the tip
 
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