Tom,
The Compufire module will not put out anymore power, than the stock points, using the same coil. You are switching the same 12 V to the coil without changing the dwell. If you want more power output, you need to use a coil with lower impedance, and, or you can use an adaptive spark ignition system that will adjust the dwell time for the optimum spark, and, or use a capacitive discharge ignition that sends a higher voltage to the coil.
Once the spark has formed, the voltage across the gap drops considerably. The voltage across the gap will be relatively constant at a given crankshaft angle. However, the resistance across the gap will change with the current through the spark. Also, the voltage across the gap will vary with changes in cylinder pressure as the crankshaft rotates. Once the fuel mixture begins to ignite, the voltage across the spark plug gap drops even lower.
After the spark has formed and the voltage across the gap has dropped to a few thousand volts, most of the Bosch coil's output is wasted by the high internal loses of the coil. A Jacobs coil, which has much lower losses, has the capability to put out over 3 times the voltage and current than the Bosch coil does into a normal spark. (I've measured this.)
Also, the low loss Jacobs coil can fire severely fouled spark plugs when the Bosch coil can't. A Jacobs coil doesn't require perfect engine conditions to fire the spark plug, and keep it free of fouling deposits.
While the Bosch blue coil may have the voltage to fire a wider spark plug gap, with a spark plug in good condition, the current through the spark is much lower than with a Jacobs coil. The Bosch coil puts far less power into the spark plug gap.
Platinum plugs will arc-over at a lower voltage than normal spark plugs. As a result, there is less power in the spark plug gap, and less power to ignite the fuel mixture. Fine wire electrodes will have the same effect.
If you use an improved coil and switch the coil with the Compufire, you will still need to use a ballast resistor.
If you use an adaptive spark ignition unit, such as a Jacobs, you can eliminate the ballast resistor for more output. The Compufire module will trigger the Jacobs ignition (and others) quite nicely.
I tested a Jacobs Ultra Coil with resistance added to the primary to equal the 2.8 ohms resistance of the stock Bosch coil. The ballast resitance caused the output to drop 16 % with 100,000 ohm load, which is in the range of a normal spark resistance before the fuel ignites. The common Bosch Blue coil, has an internal ballast resistor which cannot be removed.
As cheap as you can find Jacobs ignition systems and ignition coils on ebay, I'd suggest that you try one. If you don't like it you can resell it for what you paid for it or more. I bought one Jacobs ignition system on e-bay for for $35 and sold it $132.50 two weeks later. You just have to be a smart shopper.
Of course, once you've tried an adaptive spark ignition system like a Jacobs, it's not likely that you will want to go back to a stock ignition system. At present, I've got two Jacobs ignition systems. One is capacitive discharge and the other is an inductive switcher. I haven't decided which one I like best.
Ask your well established mechanic why there should be any performance loss with a wider spark plug gap, if you have an ignition system that is capable of delivering a high current spark into a wider gap. I have my doubts that you receive a logical answer. I'd like to hear what ignition system he used to make his conclusions.
Scott Novak