So, what exactly is the advantage of running two coils, and how is it done? Do you run a dual point and fire off two coils?
The advantage to two coils is generally a longer period of time with the points closed or longer dwell time. To do this two sets of points are required along with a rotor that can connect to two coils - special distributor. Back in the late sixties I ran a DH Du-Coil distributor. I had a four lobe cam, two stes of points - NOT connected to each other adn the cap had two coil plugs. The points in this distr. work at half the speed due to the four lobes and therefor ar more stable to a higher RPM. once set up it was great, getting it set up wash a true ***** due to the points having to be adjusted EXACTLY alike or the timing would be a little different set to set. VEry cool piece, but has been byp***ed by electronic trigering of the coil and the development of coils that deal very well with high RPM's. I hope this is clear - maybe clear as mud?
I think the idea was to split the load. Each coil was used with only 4 cylinders, and the spark was stable throughout the range of RPM. Very complex contraption, as are all rube goldberg machines The CD Ignition and electronic distributors have made those and the magneto history. People put them on cars now, because it's nostalgic, not for performance reasons.
You will need a special dual coil distributor. There were a few different designs made in the 40s, 50s and 60s. Basically it consists of 2 complete and separate 4 cyl ignition systems housed inside one distributor. Each set of points and each coil fire only 4 times a revolution. Back then "point bounce" was a limiting factor for high RPMs. With one set of points opening and closing 8 times per revolution they had a tendancy to bounce at the high RPMs. The spark became more consistent when only opening 4 times per rev. The idea started in the flathead era but became more popular with the higher winding OHV engines of the 50s-60s
I had a Mallory Double Double Life distributor on my '56 Chevy in 1962 - 1964. It a single coil, a 4-lobe cam, dual points and each set at .019" gap - 17 degrees dwell and it had dual external capicitors. I used Delco Packard 535 bulk ignition wire which had orange heat proof insulation with 20 strand, silver clad copper conductors. That ignition system was a pretty good set up. The car had essentially a 1963 Corvette FI engine (block, cam, heads) with a Carter WCFB 4-barrel instead of FI. I cannot recall which Mallory distributor used dual coils, if any. An ***ociate had a Mallory Rev-Pol on his '57 Chevy and it used a single high output coil, just like my Mallory Double Life.
Some of the traditional dual coils were entirely aftermarket, others were one-off creations or kits to convert stock distributors, a number were conversions of DC distributors from luxury cars of the thirties. In rodding, there were simple conversions for '46-8 and '49-53 Fords, along with more complex manufactured kits for other years, and Lincoln H type V-12 distributors were very commonly converted to work on V8 Fords. There probably is little need for this with modern coils...early coils had difficulties with 8 cylinders and 4,000 RPM, modern ones do not, but the tech is very cool and some of the conversions are interesting amateur projects. Dual POINT distributors based on Mallory patents, like the '32-49 Ford, are a differnt approach...two sets of points with overlapping functions allow a single coil more time to recharge between sparks. This was a critical point in the development of the flathead, because it was pushing the limits of early thirties coils and a dual coil setup would have been a very expensive bit in the low price car market.
Hey, thanks for all of the replies and clearing this up. Also of interest, Since this post, I came across an old street racer AMC Hornet that was running a dual point distributor, but used a toggle to switch between the two different breaker point. The idea was that because of the difference in degrees, one set was used as a "retard" set that was to compensate for running a secret nitrous system. Then when wanted, the driver could switch back to "normal mode", with no boost. Supposed to have worked well. Interesting, and a definite direct approach to the problem (which of course is now remedied in your CD box). The HAMB- what a great forum for discussion!
It's real simple !! Basically a seperate ignition system for each side of the engine. 1 coil,1 set of points and condensor for each side >>>>.
Just ran a couple Du-Coils on a machine last week. Got to be the steadiest spark ever at high rpm. This one we machined for a flathead ford ( it was a chevrolet v8 unit) Two coils, two sets of contacts . Like the guys said above , gives a longer coil build up at higher rpm than a single or even dual point system.
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