Is there any advantage to going with a MSD coil in an otherwise stock dura- spark system?If so what is the recommended plug gap if I go with the supposedly hotter coil?

 

I wouldn't expect any improvement unless your old coil in going bad. The coil and the duraspark both limit the available current.

 

Keep your stock plug gap. The aftermarket coil may burn up the ignition module. The stock system works well. Just use high quality OEM type replacement parts. Avoid the cheap stuff.

 

i have a blaster 2 coil in my 78 love it sends tons more spark. i shanged plugs and wire at the same time and they still look new when i took them out

 

Stay with the stock system, you are throwing your money away with any aftermarket system.

 

Thank's for the input.

 

i wouldnt consider it throwing away money. more spark = more fuel burned. do you consider water wetter and synthetic oils a wast of money to. same concept

 

the duraspark limits coil output so it is pointless to use a aftermarket coil.

 

The spark plug gap limits the secondary voltage to a value that is safe to use with all of the other components, wires, cap, rotor, coil, etc. If you increase the voltage the weakest point will arc over. You can play around and find that weak point but at the price of fuel finding it would be costly... Not to mention the cost of failed components.

 

Exactly my point Eric!! The MSD coil will not make "more spark" over the OEM coil!! As you said the coil secondary voltage produced is determined by the plug gap, and combustion chamber conditions (pressure, fuel-air mixture, etc.).

 

The stock spec gap is set up to accommodate erosion of the gap that causes it to get wider over time. If the gap is increased initially then you can expect trouble later on. I have seen people that increase the gap until it misses than back off. Unfortunately that will work for a few thousand miles until erosion increases the gap again. Then you get a very costly miss that will drain your wallet without you realizing it.

Stick with the stock gap specs and the stock type plugs. You could increase it 0.005" or so if you want. Replace the plugs at the recommended intervals.

The DS output stage combined with the impedance/resistance of the coil and the ballast resistor limits the current thru the coil primary. If either component changes resistance the current thru the primary will change. If the coil resistance is lowered the current increase thru the ignition module can overheat it. Heat is the biggest cause of electronic failure. Conversely if the ignition module is "upgraded" the increased current flow thru the coil can cause the coil to overheat and fail. If the ballast resistor is bypassed in the run position the increased current will cause the coil and/or module to fail. The ballast resistor in a Ford is a special wire built into the harness and they have been known to fail also because of component changes or someone wiring something like an electric choke to them.

 

So what your saying is if you use a "hotter" coil or performance coil with a lower primary resistance the module may overheat or burn up and fail. What is the primary resistance for a coil on a Duraspspark system or maximum current it can handle on the coil primary side? This will limit the amount of milijules output on the secondary or plugs. Higher secondary milijules output is higher heat energy output to the plug hence bigger spark kernel and a better ignition of the combustable gasses.

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The listed primary resistance of a DS-II coil is 1.0-2.0 Ohms but that is not close enough to make design decisions. It is only for service reference. You would have to measure several known good coils to get a better average value. I would not deviate more than 10% from the OEM specs which will not help you a worthwhile amount on the spark energy.

The primary ballast resistor is listed as 1.30-1.40 Ohms.

 

Thanks Eric, has anyone measured or have a Ford spec for the ignition wire resistance in the factory wiring harness?
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I already posted that info in the post above.^^^