A recommended HEI site says this:

"Using this system, the troublesome ballast resistor can be removed if you run an aftermarket coil."

What is the significance of "aftermarket?" How might OEM (or NOS) be inferior to aftermarket? Is there any particular output voltage to look for? Some are REALLY high.

I would think it means a coil designed to run at full voltage, not neccesaily aftermarket...

1) The stock coil works OK without a ballast resistor if you're using HEI, it's just not the best coil choice (not optimized for an HEI-type system). See here.

2) Please downsize your signature picture as you've already been asked to do. Thank you.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I did that before I even saw your PM. I don't know how it changed sizes on me.

Yes, I have a copy of that thread on my computer and have read it several times. But it doesn't say anything about actual output voltage I asked about or why the author used the term "aftermarket" as the answer to getting rid of the ballast resistor. Enquiring minds want to know!

Thanks.

Ross,

The HEI module is actually meant to drive a different style of coil than the original oil filled canister coil. The HEI moudule limits the coil current which is why no ballast resistor is required. Yes, other applications such as 12V VWs use different coils that do not require a ballast resistor, but that is not the case here. What are your specific concerns regarding the ignition coil? I can always pull out my dedicated copy of Dr. Chris Jacobs book The Doctor's Step-By-Step Guide to Optimizing Your Ignition if needed.

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Joshua

Ack, please don't!

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Too many people who were born on third base actually believe they've hit a triple.

What about a Mallory Mag-Spark coil?

I'm just trying to make sense of the various aspects. I can remember things better if I get an idea about the "whyfors." I do recall someone declaring they had a 20,000 V coil available, which I'm not sure I should even believe, considering I see much smaller figures regarding /6's.

I now have a Mopar EI distributor with single pickup and vacuum and centrifigal advance, so I'll need a coil before installing it in my '65, but I have no real worries about it.

Thanks

All kinds of kv numbers are applied to coils. The stock HEI coil is capable of approx 45,000v (45kv). "Performance" coils are often marketed with kv claims (50,000v coil! 60,000v coil!). This number is irrelevant, for there is a certain amount of voltage needed to jump a gap of a certain width under certain compression characteristics, and there's no such thing as forcing more voltage across the gap. (If the spark plug gap is increased, however, voltage goes up).

A "high performance" ignition system can supply greater voltage and/or current, but that doesn't mean that it will. The difference isn't what goes across the gap of the spark plug under ordinary circumstances, it's what happens under extraordinary circumstances.

Increasing the spark plug gap, increasing the compression, running a dirty spark plug (either through neglect or because some other thing you've changed allows the plugs to get dirty, e.g. a "big" camshaft left to idle)—all these things increase the amount of power required to jump the gap. A stock ignition system may not be able to provide that much power, with the result being a misfire. A high-performance ignition system has greater power potential and so will go ahead and fire the plug.

This is very, very commonly misunderstood, thanks in large part to the marketing tactics used in selling "high performance" (actually high performance POTENTIAL) ignition components.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

It sounds like one would need a "high performance" coil if he hasn't taken very good care of his normal system. Just another indication of why I should keep up maintenance.

Thanks.

You only need a certain voltage to ionize the spark plug gap. After that it takes current at a much lower voltage to maintain the spark. I don't know what Dan's problem with Dr. Jacobs is, but he's right on the money when he says current is more important than voltage. If you can get more energy into the ignition you can get higher current and higher voltage but current is more important. Too much ignition energy is also bad. For one thing it's hard on parts like the cap and rotor and also on cheap wires. It's a lot like using a cheap hose under high pressure. There are other concerns, but I don't want to confuse the issue.

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Joshua

The "doctor's" book is mostly a long ad for his products, which are IME poorly-backed garbage. Most of what doesn't constitute advertising in the book is available in any decent electrical-electronic fundamentals text from the public library, though I will give credit to Jacobs for presenting these principles in a clear and easy-to-understand manner.

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Too many people who were born on third base actually believe they've hit a triple.

Thanks

That's interesting as his book covers more aspects of ignition systems than any other text I've read. Most electronics fundamental texts would cover the theory of the primary wiring system of a vehicle, but touch little, if at all on the ignition secondary system. Dr. Jacobs covers a very wide range of products and in fact recommends products other than his own. I don't know if you were aware, but he is no longer is associated with the company which, BTW, has changed hands for a second time and most of the real Jacobs' engineered systems have been dropped.

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Joshua