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To review the basics (always a good idea) of how a piston engine works; go here: How Stuff Works / Engines
To review the basics of how a magneto works; go here: How Stuff Works / Magnetos
Choosing a Magneto

When choosing a magneto ignition, it might be a good idea to select a unit, which will meet the needs of your application without sacrificing reliability. You should consider that a unit, which is more powerful or exotic than your engine actually requires will also be less reliable and may require nearly constant maintenance. Before you go "overboard", take a minute to think it over and just be aware that the generating capacity of the magneto is directly proportional to the frequency of the service that will be required to keep it functioning at it's optimum. The extremely large and powerful magnetos in blown alcohol and nitromethane fueled funny cars and dragsters are pulled from the engine and checked after nearly every run. Is that what you want to have to do? Do you really want to live with the demands that the most powerful magneto available will place on you?

Our goal at Don Zig Magnetos is to provide information and guidance, based on our years of experience, that will help customers make choices that make them happy and satisfied with the magneto they choose. Because even the simplest magnetos we sell are very powerful, our basic position is that the magneto that will do the job without adding any complications is the best choice.

However, if you have always desired having the most amazing and powerful magneto money can buy; we will be happy to sell it to you and service it for you when required.

Will I harm my engine by using a magneto?

Absolutely Not. No matter which Don Zig magneto you choose to buy for your engine, no matter how high the amperage rating of that magneto is, the fact that the ignition is now supplied by a magneto will not harm your engine in any way. Magnetos do not cause your engine to run hot, lean out or burn up parts. Magnetos are in fact the most consistent, durable and reliable ignition system ever devised for the internal combustion engine.

Consider this fact for a moment. Every conventional piston engine aircraft that you have ever seen flying, in your entire life, no matter who manufactured the aircraft or the engine, no matter where you were at the time, had a magneto ignition. Out of all the possibilities for ignition systems available to them, no engineer has ever used any other type of ignition system on a piston engine airplane. Would they do that if magnetos caused premature failure of engine parts or weren't the most reliable and powerful ignition system available?

No ignition system makes a more powerful [higher amperage, longer lasting] spark than a magneto and the faster you spin them the more powerful the spark becomes. This characteristic does not harm your engine; it makes it more powerful and reliable. If you have seen magneto-equipped engines that have had engine failures, it was do to the fuel air mixture or the ignition timing be incorrectly adjusted or to various engine components being stressed beyond their performance limits, not because the spark that set off the combustion process was "too hot".

What kind of spark plug wires should I use with my magneto?

The goal is to deliver a spark to the plugs, which is the most powerful, and of the longest duration that we can. If we route the spark to the plugs utilizing wires, which deteriorate the spark because of resistance or impedance, we are defeating our goal. For this reason, we must use wires of the highest conductivity. The type of wire that features this characteristic is silver plated copper core wire. If we have a magneto, which uses an external coil, we use this same type of wire as the coil wire lead from the coil to the cap.

Don Zig Magnetos is a factory authorized Mallory dealer and we sell the finest quality solid core spark plug wires and insulated sleeving. You will find them listed on our Mallory page.

Data Retrieval and Acquisition: Shielding

When using data recorders or memory tachs it is essential to "shield" all of their associated wires from the magneto and ignition (spark plug) wires. The powerful radiation & electro magnetic forces emitted by the magneto and ignition wires will interfere with the proper functioning of a data recorder. The user, when encountering trouble, may call the data recorder manufacturer and their standard answer to cure all woes is " change to suppression type ignition wires".

This is really not a satisfactory solution and you shouldn't do it. Performance will be adversely affected by suppression wire. Suppression wires runs 30 to 50 ohms resistance per foot. A standard wire runs about 1 to 2 ohms resistance. The goal is to achieve the most powerful spark possible at the plug gap. Using suppression wires defeats this goal.

The answer is in shielding the data recorder from the electronic field emitted by the ignition wires and the magneto. Commercial braided shielding is available at good electronic stores and can be used to shroud the data recorder and its wires. Even a simple aluminum foil shield will help suppress the radiation & noise. Shrouding the ignition wires in braiding will also help to eliminate the magnetic noise radiated by the ignition system.

For a complete technical discussion of electrostatic interference and how to shield against it: visit the Alpha Wire web site.



  • 1. If the ignition has points; it fires when the points open. This is true for both battery operated and magneto ignitions.
  • 2. A buzzer is a simple device that indicates just when the points open.
  • 3. Advance is thought of in two different ways; the ignition and the crankshaft. Racers deal in real time or crankshaft degrees, while engineers and servicemen deal in half time or ignition degrees as the ignition is one half engine speed. Racers also deal in total degrees at the crank. If you have an ignition with automatic advance, you have some kind of system to advance or retard the ignition. If your ignition is "locked out", this means there is not an automatic system and the movement is "0" degrees.
  • 4. If you want to run 36 degrees and your ignition is locked out, you must set all advance on the crank pulley. If you wan to run 36 degrees and your system has automatic advance, that advance must be determined before you start. For ease, let's say your ignition has 20 degrees automatic and you want to run 36 degrees total - 36 degrees subtract 20 degrees equals 16 degrees. By simple addition and subtraction, you can see the crank must be set on 16 degrees B.T.D.C. If your crank is not degreed, it should be. You can buy a timing tape at most speed shops for different size balancers (or crank pulley). Some machine shops have the capability of turning and degreeing your balancer for a small charge. If you cannot find a tape or a machine shop, then you might do it yourself. Find where TDC is and mark it exactly on the pulley. Next, with a good tape ruler, measure the balancer or hub circumference and divide by 360, then multiply the answer by 10, 20, 30, 40 or what ever marks you wish to mark on the pulley. If you have a stock balancer, do not assume the "0" degree is at the right location. Many times these marks have turned on the hub and are no longer accurate.


  • 1. Determine the total amount of degrees you wish to run in the engine.
  • 2. Determine the total amount of degrees your ignition
  • 3. Through additions & subtractions, find out where to set the crank BTDC, and do it now!
  • 4. Find out where the number 1 cylinder segment is in the cap and mark on the outside case of the ignition with a marker.
  • 5. Find out where last cylinder segment in the firing order is on the cap and mark that on the outside of the ignition case.
  • 6. Line up all intermediate oil pump drives and gear drive so as to place the rotor approximately � of the way between #1 cylinder segment and the last segment in the firing order when the ignition is firmly seated on the manifold or block surface.
  • 7. At this time you should check the play between the intermediate shaft and the ignition or the block and the thrust face on the gear. Some play or clearance must be present. If not when you tighten your ignition down, you might be jacking your oil pump gear through the bottom plate of your pump.
  • 8. Put the retaining clamp on now and just snug up the bolt / nut retainer so you can move the ignition with a slight amount of resistance.
  • 9. Hook up the buzzer to the primary wire and a good ground and turn it on. The buzzer may be buzzing now or it may not , don't worry at this time.
  • 10. Determine which way the rotor rotates and hold back against it with your thumb and apply a few ounces of pressure.
  • 11. Turn the outside case of the ignition against the rotation until the buzzer just stops. You might have to do this 2 - 3 times to get the feel of it, but the mag will fire just as the buzzer stops (this is when the points open).
  • 12. Tighten up the ignition retainer bolt / nut until the ignition will not turn.
  • 13. To check if your right there in the ball park ignition wise, reach up and grasp the rotor and turn it the way you did before. It should quit buzzing and now buzz with the alternate application and reduction of pressure on the rotor.

Heads up!

These firing order diagrams show rotor rotation direction and give the location of the number one spark plug wire lug on the distributor cap. The location of your number one lug may, and in fact, most probably is, different from that shown. Your number one lug is which ever lug your rotor is pointing at when your engine is positioned so that the number one cylinder is at top dead center at the end of the compression stroke, not the exhaust stroke.

To identify the alignment of the timing marker and the "zero line" on the harmonic balancer which represents top dead center at the end of the compression stroke, just remember that it occurs just after the intake valve closes. Remove the valve cover so that you can see the valves for the number one cylinder. Identify the intake valve. It is aligned exactly under the runner of the intake manifold. The exhaust valve is exactly aligned with the exhaust port of the cylinder head. Take precautions so that the engine can not start accidentally as you rotate the engine (i.e., take out the spark plugs). Rotate the engine and watch the intake valve go down. Keep rotating the engine until you see the intake valve just begin to come back up. Stop, your close. Look down at the timing marker. Rotate the engine just enough more to bring the "zero line" on the balancer into alignment with the timing marker. Your engine is now at top dead center on (at the end of) the compression stroke.

If you have never used a magneto before; READ THIS
Magneto Users Biggest Mistakes...
Never do any of the following!

  • Never connect battery volts to a magneto.
  • Never use suppression wires or resistor spark plugs.
    Set the plug gaps at .018 - .020 for either internal or external coil mags.
    Magnetos do not require and are not more efficient with large large spark plug gaps.
  • Never weld on the car with the magneto in the motor. The generating unit may be discharged.
  • Never rely totally on your timing light as your sole source for timing your motor. Timing lights are typically D.C. and magnetos generate A.C. They also emit E.M.I. (Electro Magnetic Interference). In general, timing lights with mags are one (1) degree late for every 1000 RPM of engine speed. For best results, use a timing buzzer. We sell them and you can see one at the bottom of our products page.
  • Never operate a magneto without all of the plug wires connected to the spark plugs.
  • Never run a cast magneto drive gear against a steel billet camshaft. If there is any doubt which gear to use, contact the cam grinder.
  • Never force a drive gear on the shaft when changing or installing the gear. It may change internal clearances in the mag.
  • On a single mag warm up with a duel mag drive system and Mallory mags; DO NOT disconnect the second mag from the transformer. Severe damage to the mag generator will occur if you do.

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