I made a lowball bid on a Mallory "Magspark" unit on eBay, because I wanted the brass condenser on it. To my surprise, I won it and received it Saturday. I did a search and came up with some literature on it. If what I surmise is correct, it is actually a coil with two primary windings and one secondary. The dual points in the distributor are disconnected from each other and wired so each set of points drives each primary winding, causing the secondary winding to fire. (You may correct me if I'm wrong). I am intrigued by this thing and would like to try to use it if I can. I would like to do a preliminary test with an ohmmeter to see if it is any good. My question is : Should the primary and secondary windings have similar resistance to those of a good conventional coil? I can't see why not.
Here's a bump for the night owls. Good question and I'd like to hear what wisdom is out there too.....
Well, 'similar' is a rather vague thought. There can be a fairly wide range of primary/secondary resistances depending on the individual coil. Plus ratio and how the primary and secondary windings are interleaved will affect the secondary resistance and output. But as a general rule, if the primary resistance is less than about 2.5 ohms, you should use a ballast resistor to limit current for decent point life and to avoid overheating the coil. Secondary resistance should be similar to a conventional coil. I would expect this to draw a bit more current, so make sure both the ignition circuit and the ballast resistor are up to the task. Using a separate ballast resistor for each half may not be a bad idea.
Since I have the interest of at least a few of you, I'd like to throw a question out there to see if any of you have any thoughts. First of all, I am not talking 4-lobe cam units or dual coil units. A regular dual point distributor uses the dual points to obtain a longer overall dwell to better saturate the coil. Every one I have seen says to set the points to the same gap. This means that the two sets of points must be slightly out of phase (not exactly 180 degrees from each other) if they are to provide this increased dwell. The Mallory instructions I have seem to say that the same distributor can be used for both the Magspark (essentially a dual coil) and a regular single coil simply by removing the internal jumper between the points and running two leads from the terminals on the distributor to the primary terminals. If this is so, isn't every other cylinder slightly off timing? The only other thing I can think of is that the distributor for the mag spark would have a 4-lobe cam, but that is not mentioned in the insructions, while removing the jumper and using the separate terminals are. Can anyone shed any light on this?
This is a guess, but I think this was an early attempt at multiple spark. Remember, you still have a common primary; the second spark would arrive very slightly after the first, so 'basic' timing would remain the same. You may possibly see better idle quality and lower-speed drivability (something MSD ignitions are known for) but there's no high-rpm gain to be had. The downside is you have two primary coils producing heat, so coil overheating at lower speeds may be an issue.
Thanks, Steve (I can't call you "Crazy" after this), That makes a lot of sense. I think I'm going to pursue this a little further. If overheating would have been a problem, don't you think they would have put some "cooling fins" on it? That was all the rage in those days.
If this was designed as a 'Race Only' piece, they may have felt cooling wasn't needed. The thing to remember is coil saturation once power is applied takes a finite amount of time, regardless of RPM. So at lower speeds, the coil reaches saturation well before it needs to fire, and the additional time 'on' just produces heat as at that point you're just powering a short circuit. Modern electronic ignitions now feature 'dwell control', that limits the coil 'on' time to just what's needed to saturate it regardless of RPM, thus reducing coil heating.
After further research, I don't think this is a "MagSpark" at all, but a "Voltmaster" coil. It seems they used the same casing, but the third terminal at the bottom of the unit was not used and was covered by a red plastic cap. This unit had that red plastic cap still on it, which made me wonder why it would have stayed with the unit for all of these years. I'm going up to my shop tomorrow and will check out the connectivity between the terminals, which should tell the tale. "302GMC" if what I say is true, you may have a bunch of vintage Mallory coils on your hands, not a bunch of nondescript "MagSparks".
Hello, all. Fairly new here... Let's see if I can help. You can find some good info in the copies of old Mallory forms posted by CHRX at this thread: https://www.jalopyjournal.com/forum...ark-distributor-and-a-regular-mallory.351824/ . There are four separate posts that each have scans of the old forms, which do a thorough job explaining hook-up for Magspark dizzy and transformer, or dual-point with Voltmaster or "Best" coils. The .pdf's include part numbers, and show a few views of coils, although there are newer coil variants not shown. The older Voltmaster coils did not share a common housing with the Magspark transformer, although I have seen some newer units that have the red cap you mention. I didn't see an earlier question answered, so here goes: The Magspark transformer used in conjunction with the Magspark distributor saturates two separate primary windings around a "donut" shaped rectangular core in the transformer (see attached image of an old ad). The breaker points which close separately cause the magnetic field in the two arms to start collapse separately, but around a single core, with a single secondary winding, I don't think it produces two distinct voltage spikes or "sparks," so to say. In any event, in "normal" dual-point style, spark is timed correctly by distributor position, just like a single point dizzy. Cheers!
One more point, while I'm thinking about it. According to the old Mallory literature, the resistors on the old Magspark transformer and on the "Best," Voltmaster, or Flash Fire coils don't work like a conventional dropping (ballast) resistor. They are designed to hold the voltage at the coil relatively constant regardless of charging voltage, and are also designed to keep the current through the points somewhat lower than with a standard dizzy/coil to increase point life. Even the old Mallory 6V coils used a special resistor. What's the point? - don't expect the primary resistance values to necessarily be the same as a conventional coil that uses a conventional ballast resistor or wire, although the values should be roughly similar. If I understand the old Mallory logic, the primary resistances will be somewhat higher. I just snagged a NOS Magspark transformer of what looks like mid-50's vintage. If I find out anything more interesting once I have a chance to measure it, I will post that. Cheers!
I installed Mallory Magspark systems on 6 and 12 volt 50's vehicles using both Magspark breaker plates & Mallory distributors. Best ignition system then. It used a transformer instead of an induction coil. The transformer had normal and reverse primaries. The 'normal' primary driven by one set of points & the 'reverse' primary was driven 7 deg later by the second set. This gave a forced flux reversal when the first points opened, with a fast-rise 50 KV first spark and a normal 20 KV second opposite polarity spark 7 deg later. Nothing equal until capacitive discharge systems. Aside from point wear it's still right up there.
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