Distributor Issue:

[James Vincent]

Hi, can anyone tell me if I can use a magnetic type distributor without an external ballast resistor? The coil is reading 11 to 12 volts... so wondering if this can cause damage without the ballast resistor. Or is the ballast only needed when breaker points are fitted?
Any info appreciated!

 

[Don C]

You have to use whatever your distributor requires. The instructions for it should tell you whether it needs battery or reduced voltage. Different manufacturers have different requirements.

 

[mrgmhale]

Hi, can anyone tell me if I can use a magnetic type distributor without an external ballast resistor? The coil is reading 11 to 12 volts... so wondering if this can cause damage without the ballast resistor. Or is the ballast only needed when breaker points are fitted?
Any info appreciated!

If you are using an oem Ignition Coil, the voltage needs to be lower than battery voltage while the Ignition Switch is in the Run position, as excessive voltage will cause it to run too hot. The 1973 Ford Shop Manual states the voltage at the positive terminal of the Ignition Coil should be between 4.5 and 6.9 volts when the negative terminal is grounded (simulating closed ignition points). If you are using an aftermarket Ignition Coil the voltage required could be either the same as an oem Ignition Coil (4.5 - 6.9 volts), or full battery voltage IF the coil is designed for full battery voltage (not all are designed for 12 volts).

I know the Pertronix Ignitor 1 version of their aftermarket electronic ignition system requires the resistor wire to be in place for the Ignition Coil, although they want full switched battery voltage for their Ignitor I Module (#1281) inside the distributor. If you use their Flame Thrower 1.5 or 3.0 ohm aftermarket Ignition Coil (40001, 40011, 40111, 40501, 40511, & 40611), those specific coils require full battery voltage to operate properly as well. Other electronic ignition systems will have different Ignition Coil voltage requirements depending on the coil being used.

 

[James Vincent]

If you are using an oem Ignition Coil, the voltage needs to be lower than battery voltage while the Ignition Switch is in the Run position, as excessive voltage will cause it to run too hot. The 1973 Ford Shop Manual states the voltage at the positive terminal of the Ignition Coil should be between 4.5 and 6.9 volts when the negative terminal is grounded (simulating closed ignition points). If you are using an aftermarket Ignition Coil the voltage required could be either the same as an oem Ignition Coil (4.5 - 6.9 volts), or full battery voltage IF the coil is designed for full battery voltage (not all are designed for 12 volts).

I know the Pertronix Ignitor 1 version of their aftermarket electronic ignition system requires the resistor wire to be in place for the Ignition Coil, although they want full switched battery voltage for their Ignitor I Module (#1281) inside the distributor. If you use their Flame Thrower 1.5 or 3.0 ohm aftermarket Ignition Coil (40001, 40011, 40111, 40501, 40511, & 40611), those specific coils require full battery voltage to operate properly as well. Other electronic ignition systems will have different Ignition Coil voltage requirements depending on the coil being used.

View attachment 91141

Thanks for the info. I only see a part number on my Motorcraft distributor i.e. 12127 so it's a challenge to find any info on its requirements.

 

[Stanglover]

Is the picture you posted what you currently have in your car? Also, what year and model is the car, I didn't see that in a description.
What you show is a DuraSpark electronic distributor, in which case, is a good unit. I'm personally not familiar with the DuraSpark Ford distributor, but others are and will better assist you setting it up.
In my car, 351C 4V, I'm using a Pertronix Ignitor II with matching Flamethrower coil. That does run on FULL voltage and bypasses the resistor wire. I also recurved that distributor to allow more initial timing. That's for later help if needed.

 

[Hemikiller]

As Stanglover noted, that's a Duraspark distributor. What do you have for an ignition box? There are several types of D-spark boxes, one runs full battery voltage to the coil, the others use a resistor. If you have another type of ignition box like an MSD, then that manufacturer will dictate what voltage goes to the coil.

FWIW, if you're simply testing voltage with the ignition on and the engine not running, you will always read battery voltage. The resistor will not drop voltage until there is a load applied - which means the coil has to be charging like in mrgmhale's illustration. The lead grounding the coil (-) terminal (distributor side) causes it to charge.

 

[Spike Morelli]

I think I have a '72 Duraspark distributor in my parts cabinet for a 351c/ 429-460. Who knows why I have it, or who's it was. It can be like an archeological dig to look into stuff I have sometimes .

 

[Don C]

Duraspark coils typically use the reduced voltage from a resistor circuit. The Duraspark box requires full battery voltage.

 

[James Vincent]

Is the picture you posted what you currently have in your car? Also, what year and model is the car, I didn't see that in a description.
What you show is a DuraSpark electronic distributor, in which case, is a good unit. I'm personally not familiar with the DuraSpark Ford distributor, but others are and will better assist you setting it up.
In my car, 351C 4V, I'm using a Pertronix Ignitor II with matching Flamethrower coil. That does run on FULL voltage and bypasses the resistor wire. I also recurved that distributor to allow more initial timing. That's for later help if needed.

Yeah, the picture is the distributor currently in the car. The Mustang is a 1974 but was custom built... so has a 1971 Windsor 302 5Lt. in it. I also wonder if the Ignition Control Module is compatible with a bigger engine... as the 1974 Mustang had a 2.8 Lt. in it. So is DuraSpark a brand name under Motorcraft because Motorcraft is stamped on the distributor? I got some info on the coil since and it said; "use with an external resistor" but this wasn't written on the coil. It seems any original resistor or ballast was removed from the car... as I get a 12 volt reading on running position.

 

[Don C]

Yes, DuraSpark is a Ford (Motorcraft) model name. The DuraSpark ignition came out in 1977. The electronic ignition that came out in 1974 was called Breakerless Ignitions. The easiest way to tell the difference is in the connectors. Both come with two connectors, the breakerless ignition has a 3 wire connector and a 4 wire connector, the DuraSpark has a 2 wire connector and a 4 wire connector. The ignition control module is not engine size related. The most sophisticated and desirable control module was the DuraSpark 1 with a red strain relief connector.

 

[Stanglover]

Yeah, the picture is the distributor currently in the car. The Mustang is a 1974 but was custom built... so has a 1971 Windsor 302 5Lt. in it. I also wonder if the Ignition Control Module is compatible with a bigger engine... as the 1974 Mustang had a 2.8 Lt. in it. So is DuraSpark a brand name under Motorcraft because Motorcraft is stamped on the distributor? I got some info on the coil since and it said; "use with an external resistor" but this wasn't written on the coil. It seems any original resistor or ballast was removed from the car... as I get a 12 volt reading on running position.

Sounds like you have a mish-mash of parts there by a "creative builder". All god if it all works.

 

[mrgmhale]

Thank you for the photo of the inside of your distributor. That is definitely a DuraSpark electronic ignition stator and reluctor you are using. There are several flavors of DuraSpark. With your Ignition Module, where the external wires from its multi-wire connectors go into the module, what color is the grommet? It is usually blue, red, or black. I have seen other folks report green, and yellow grommet also. Once I know the color grommet you have I ought to be able to determine what version of DuraSpark you have, and from there ascertain the voltage on the positive primary terminal on the Ignition Coil.

 

[James Vincent]

Thank you for the photo of the inside of your distributor. That is definitely a DuraSpark electronic ignition stator and reluctor you are using. There are several flavors of DuraSpark. With your Ignition Module, where the external wires from its multi-wire connectors go into the module, what color is the grommet? It is usually blue, red, or black. I have seen other folks report green, and yellow grommet also. Once I know the color grommet you have I ought to be able to determine what version of DuraSpark you have, and from there ascertain the voltage on the positive primary terminal on the Ignition Coil.

View attachment 91186

View attachment 91185
View attachment 91184

Yeah, it's a Blue grommet. It seems strange that the 'red' wires on the 2 wire connector are not lining up. I'm only getting a 1 volt drop difference between engine running and ignition being switched on... so I still can't tell if there's a resistor in the wiring loom. At a loss to know if I buy a new coil... should I get one that doesn't require an external resistor.

 

[James Vincent]

Yeah, it's a Blue grommet. It seems strange that the 'red' wires on the 2 wire connector are not lining up. I'm only getting a 1 volt drop difference between engine running and ignition being switched on... so I still can't tell if there's a resistor in the wiring loom. At a loss to know if I buy a new coil... should I get one that doesn't require an external resistor.

 

[mrgmhale]

I dug up these documents re: DuraSpark systems. Let me know if you need more info.

Ciao!

Gil

 

[James Vincent]

I dug up these documents re: DuraSpark systems. Let me know if you need more info.

Ciao!

Gil

Thanks for the info it was helpful!