I just replaced the stock coil on my 460 with an Accel Super-Coil (the big yellow, oil filled brick - puts out 45,000 volts) and also replaced the cap and rotor. The truck ran awesome for a week then just wouldn't start one day - no spark.

Question 1: I have the breakerless ignition and from what I read online, you don't need a ballast resistor unless you have points - is this true?

Question 2: Will running the Accel coil without a ballast resistor fry the duraspark box - or will the duraspark box fry the coil?

I yanked the coil wire from the distributor and cranked it close to a ground - no spark. Tried again with the stock coil - no spark. Grabbed a solid copper core coil wire and tried again - weak spark from the Accel, almost no spark from the stock coil.

Scratched my head and grabbed another duraspark box and hooked it up with the stock coil - nothing at first. Repositioned the coil and checked the connections - fired right up. But there was a spark arcing from the coil, to the air cleaner, and back to the coil wire - when it broke connection when I moved the coil, the motor quit.

Question 2: Is my duraspark box bad, or do I just have a bunch of junky wires?

I'm going to head out to the garage and tinker for a while I guess. Thanks in advance for the ideas guys!

 

Ok - the Duraspark ignition box was bad. Replaced it and it runs with the stock coil. So now, what ohm ballast resistor do I need to keep from frying the new Duraspark? Resistance across the poles on the stock coil is 1.1ohms and resistance across the poles on the Accel are 0.5 ohms. I take it I just need to get enough resistance inline with the Accel to make it get 1.1ohms?

 

Your "performance coil" probably pulled enough current through the power transistor in the ignition module to fry it. The point of the ballast resistor is to limit the voltage across the coil primary winding. It creates a voltage divider with the primary winding of the coil. It also limits the current through the power transistor of the module when it (effectively) grounds the coil right before firing the plugs.

The ballast resistor is used with points and electronic ignition when in stock form. I can't tell you if you need the ballast resistor for your particular coil or not. This is something you'll have to research with Accel's tech support or website using the model number. Judging by the fact that it fried your module, though, I wouldn't be surprised to find out that you need it.

For what it's worth, "performance coils" that advertise high voltage are a marketing scheme in my opinion. For a specific plug gap, there is a certain range of secondary voltage for the spark to jump across the gap of air. Any wider and the spark won't jump, or will look for a less resistive path. Any narrower and the plugs burn up faster. Ignition upgrades aren't really worth it unless everything is done in unison. The stock Duraspark II system is an excellent ignition setup.

I would say that buying that coil alone is a waste of money, but I'm not prepared to battle the backlash I'd get from others on here that swear by them (which is most often hear-say anyway). Whatever the case, any gains you would get probably aren't worth the headache you're treading through now.

 

If you have a stock vehicle with the stock wiring, your harness should already have the resistor built into it. You can check this by reading the voltage on the coil + while the engine is running. It should be something around 9v.

I agree with the previous poster, you don't get something for nothing. More spark power from a hotter coil means the coil is going to draw more current. The duraspark II box is where the current goes through the primary of the coil, so it will put more load on the module. I haven't tested any of these "hot" coils long term with the stock module, but you would think it would run hotter and may shorten it's life a little bit.

I would save up some money and buy a MSD 6a box if you want more ignition performance. Your stock dist will drive the MSD 6a, and you will not need the duraspark box anymore. And the MSD 6a will drive the new coil also.

 

Thanks for clearing that up for me guys - think I have a better understanding of the DS-box now.

My dad gave me the Accel Super-Coil - he ran it on his dragboat quite a number of years ago and decided he was going to buy an MSD Marine kit when he gets working on the motor. I fugured, hell - why not use it.

From what I've read on Accel's Q&A page, when you run a hotter coil, 45,000 volts in my application, you can open up the gap on your plugs to .055" which will give you a longer, bigger spark than when using the stock coil and plugs gapped at .045" (which who knows what the stock coil really puts out - could be crap compared to 45,000 volts).

Before my DS-box failed, I noticed a big difference running the Accel coil. The motor idled smoother and throttle response was much quicker.

I did some more research on the DS and apparently, it doesn't have the ability to switch low-resistance loads... it will do it for a short time, but will eventually overheat and fry - as I found out the hard way. One website says the DS needs to "see" at least 2.7 ohms, but when testing my stock coil, it gets 1.1 ohms, and there's no ballast resistor or resistor wire in the circuit. So, just to play it safe, I'm going to try the Accel coil again with a 1.1 ohm ballast resistor. The Accel coil is rated at 0.7 ohms, so if you figure I run a 1.1 ohm ballast resistor off the +, the DS will see 1.8 ohms, and it should live.

If money permits, when I go through the motor and get the engine compartment cleaned up, I'll get an MSD CDI system or Accel 300+ system. Right now, Ford's original messy wiring job would make tracing wires a major pain in the azz.

 

i burned up to coils wen i went from points to a msd ignition. i needed a ballast resistor with my msd coil

 

I ended up buying the 1.1ohm ballast resistor and driving the truck for a week and no problems. Gapped plugs at .050". Major improvement in throttle response!