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Discussion Starter #1
Recently reconfigured wiring to coil to get a full 12V at coil. Am now using the "pink wire feed" to merely open a 12V relay to power the coil. Of course in doing so, I have lost the signal to the tach in my Rally Pak.

What is best way to recover power signal back to tach? If I were to splice off of the pink wire feed to the relay and add to the coil post, where I already have the 12V source connected, will that work - or damage the coil and tach? In other words, my simple dumb question: is placing a 12V source on the coil post + an approx. 8V feed from the pink wire going to be additive and create an over-voltage to the coil?
 

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keyed power can be acquired at the yellow 3-way connector near the fuse box
 

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In other words, my simple dumb question: is placing a 12V source on the coil post + an approx. 8V feed from the pink wire going to be additive and create an over-voltage to the coil?
Its actually even less than 8V usually.

12V (which is really 14.5V when the engine runs) directly on a stock coil all the time will damage the coil by overheating it. 14.5V instead of 8V will put over 3 times more heat into your coil. It is meant to have 12V only when starting to counteract the reduced battery voltage while cranking the starter. Why would a tightwad like Henry Ford spend money on a ballast resistor if it wasn't needed? There is very little, if any benefit, from using a higher voltage than what Ford, and nearly everyone else used. 40, 50, 60kv coils for your spark plugs are mostly an ego trip. A spark plug in normal operation takes about 15kV to fire. The fuel is either ignited or it isn't. Once the burn starts the spark plug has nothing to do with how the flame front progresses. Excess voltage beyond what is needed can burn wires and distributor caps though.
 

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there are a lot of people out there that love motorcraft coils for their performance..don't really know why..just read it a few times on the net.
 

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Discussion Starter #5
for clarification, it is not the stock coil. It is a Pertronix Flamethrower with Pertronix Ignitor II. I want the 12V at the coil for that reason - there is a definite difference in starting when supplying 12V vs. 8V on my car.

So my question remains - is DC "additive"?
 
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