Does the Duraspark II need a ballast resistor?

[douglloyd]

Searched the archives for this - Unca Skip said yes in 2006, but I'm not sure if the Duraspark II needs this.

I'm just about through rewiring my '66 longbed (302/4speed) with a Painless universal kit. Most of the '66 schematics show a ballast resistor in place to lower the voltage to the coil after startup. Painless says this is optional, and the Duraspark articles I could find online go both ways.

The coil is stock as far as I can tell, and the last owner ran it for years(?) without a resistor, unless it was buried in the old stock wiring loom. Per the Painless instructions I've got the skinny pink ignition wire straight to + on the coil - will straight 12V cook it?

thanks,
Doug

[Phil]

I used this Mustang diagram for my Fairlane

[banjopicker66]

The resistor wire is indeed part of the wiring harness.
The Duraspark requires a full 12V to 2 separate circuits, but only for the Start cycle. I tapped into the secondary wire off the starter solenoid for the 12V during start.
For the Run circuit, it requires a resistor to work properly.
I used the original wire to the points for the resistor circuit into the new coil.

[douglloyd]

Thanks for the feedback. I did not realize that the stock harness already had something in it that could drop the coil voltage. Go to NAPA parts online and they sell a 61" length of special wire to splice in that does the trick.

I did some more digging and found a vendor (Hot Spark in Austin, TX) that sells the little ceramic block style that I can mount on the firewall and still link into my ignition line. The Painless kit does not come with any means of voltage drop, but has a pretty good schematic to follow if you have your own.

Thanks again for the help. I'm just about done with the engine wiring and have already run the lines for the lights. Next Saturday I tackle the instrument panel and switches.

thanks,
Doug

[Jonas]

You can buy the ballast at Advanced.

http://shop.advanceautoparts.com/Produc ... ber=AL125K

[BackyardRest]

I have a bunch of NOS ford resistor wires if OEM is needed.

What I like to do is use the DuraSpark distributor but a hidden MSD ignition box then that wire or resistor is not needed and they run much better.

[blackagatha]

I dont know what the resistor is for.... When I put the Pertronix in my dizzy, I did as reccommended and gave it a full 12v. (ie disconnected resistor wire and ran a fresh switched hot wire to the coil) SO, Ive been running 12 volts on a coil (that does in fact specify the use of a resistor) for 3 years now with no trouble whatsoever.

And now with the MSD setup.....

Do you guys realize what that thing does? Apparently It shoves 480 volts into the coil, and I'm guessing, halfway shorts it out in the process of its 3x the spark ordeal.

And there is no trouble with the coil.... Weird stuff guys.

so, what I'm saying, it can the resistor. They be silly. (unless you have points still, then they'll get all roasty.)

[66camperspecial]

When I put the 351 in my 55 sunliner I never hooked up a resister and it has worked fine.

[Missouri66]

The ignition resistor was originally wired into the ignition circuit to drop voltage in the primary ignition circuit (in front of the coil) from 12V to about 9V. The lower voltage reduces arcing across the points in normal engine operation and extends ignition point and condenser life.

For the starting cycle the resistor is bypassed (hence term bypass resistor) to deliver higher starting voltage.

I'm not familiar with all of the electronic ignition setups, but since the ignition points are eliminated, I would think the resistor may be unnecessary as well.