[TimG]

I have a mallory unilite distributor that is running off the stock coil that I used for my old distributor. Is there a big difference in how well the engine will run with the stock coil versus an aftermarket coil for the distributor.. If so, what coil should I look into buying?

 

[Tom Mobley]

>>Is there a big difference...<<

Nah. This is a heavily hyped area of hot rod parts sales, but there's no free lunch in electricity, either. Manufacturers can vary the ratio of primary windings to secondary windings, this manipulates the maximum output voltage, but the tradeoff is that the amperage is reduced by a corresponding amount. If some coil is advertised as producing a gazillion volts, then there's probably no amps at all. I've now gotten to where I don't think there's much of anything to be gained until you move up to a system that doesn't use a resistor on the input side of the coil, like a GM HEI, for instance.

If you do want to have a fancy coil, look up what Mallory recommends for the distributor you've got. Probably one of those big square black ones. They're pretty reliable, unlike the big yellow ones. There's some small round red ones that seem to work OK too.

Does your Unilite have a vacuum advance?

Tom (if you have a small round black one that says "Delco-Remy" on it, I'd consider keeping it if it was me. They make good sparks, last forever.)

[This message has been edited by tommob (edited 05-19-99).]

 

[DZAUTO]

Tom,
So if you up the voltage and at the same time lower amperage, what is the direct effect at the plug gap? For example, if a Delco coil is replaced with an MSD Blaster 2 coil to provide more voltage, what's the net effect?

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[Steve S]

The advantage of higher voltage is you can widen the plug gap and get a better spark. The advantage of lower current is you lengthen the life of the plug. All this only leads to a slight power gain but a definite driveability and plug life gain.

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Steve Strasemeier (70SS 396, Fathom Blue/White Stripes)

 

[jholp]

Tim,

I put a Mallory Unilite distributor in an engine recently and called Mallory to ask basically your same questions. The engineers there recommended their 40,000 volt coil and made a big thing about the in-line resistor.

So I purchased all three items and things worked well. The Mallory Unilite does NOT want 12 volts, it will damage it in time - over heat. Also the resistor gets quite hot so mount in in a place where it cannot do damage. I mounted mine on the rear of the engine bell housing, there were a couple of small threaded holes back there not being used.

John

 

[Kevin]

Provided your battery and alternator are in good shape you will not reduce the coil output current as you increase the coil output voltage. This is because the primary coil will just draw more current. I do agree that for the most part that unless you have high compression or rev to 7000 a factory type HEI (or Unilite optical) ignition is sufficient. I mean you only need a little spark to explode a gas/air mixture.

Just to babble on, I have noticed that a MSD box will provide a better idle and a smoother low end but does little for peak power on my mildly modified engines.

 

[Ken M]

There is a book published by Bruce Jenkins (Pro Stock Driver), he discusses how increasing the energy of the coil, does not directly increase engine horsepower. However he does imply that increasing the coil output does allow for a wider gap, which does increase horsepower slightly.
Coils not only provide for a certain voltage output, but are also capable of storing energy. Notice how the Accel Super Coil are much large than a stock coil. There is a difference in primary to secondary windings, providing a higher secondary output voltage, but they are also larger because they can store (or build) a large flux density.