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Another Fun thing Ignitions!


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There's no question the best idea for ignitions has always come from the General.

When Billy Durant bought Dayton Electric he got Charles Kettering who wasn't really an engineer, he was a scientist.

Automotive ignition systems where pretty primitive in the early cars, most were vibrator coil types run on dry cell batteries in mass market cars and magnetos in expensive ones.

Kettering is the genius who gave us the "battery coil" type we know as the "Point type" ignition.

Durant also bought Remy which had a very poor reputation and merged them with Kettering's Delco (which had a good one) to make Delco-Remy.

The gold standard for ignitions with distributors is the GM HEI, mostly because they've made so many of them and they work well.

That means the aftermarket is full of innovations like Multi-spark units. We can enjoy the benefits of HEI from Langdon's StoveBolt.

BUT they are 12 volt only.

So what to do if you want to stay with 6 volts?

Well I am glad you asked!

During the 1960s there was an outfit in Grand Junction, CO called Delta Products, Inc. that made the ubiquitous Delta Mark Ten CDI.

These were sold as assembled units and kits a hobbyist could build. Add to that the Delta Mark Ten B units were sold by Radio Shack (Archer & Micronta) and HeathKit.

At Delta's peak they employed 500 people! So they were not a flyby night outfit by a long shot.

6 volt Mark Tens are rare and positive ground ones are rarer still. Delta never made a "B" model in 6 volt. The "B" model adds a switch to revert back to point ignition and that's all.

So what's the big deal?

A Capacitive Discharge Ignition fundamentally changes the way an ignition makes a spark and the type of spark.

In Kettering's ignition when the points close a magnetic field builds in the coil. When they open the field collapses and a spark is delivered from the coil secondary. The points see an electrical load from the field and when they open the field still wants to draw current through the points so there's a spark at the points as well when contact is broken.

In CDI the spark is produced by a capacitor discharging the current stored in it. The ignition coil is now used as a transformer to step up the voltage of that discharge.

By using the points as a SIGNAL for the circuitry to charge up the capacitor instead of acting as a SWITCH to build a magnetic field in the coil, less current passes through them and they last a very long time.

The Kettering Ignition produces a slow building spark that has a long duration, where as CDI (including HEI) is very quick acting and thus very intense. Imagine it this way the maximum most stock coils put out is around 40,000 volts, if you pack all those 40,000 volts in a shorter burst it is going to be intense! That long slow building spark erodes the plugs and if there's anything that would impede the spark, it does. That's why all the old 2 stroke SAAB owners loved the Delta Mark Ten.

So is CDI going to make your car faster?


However, it will make your points and plugs last longer.

In the old days a tune up would last 6,000 miles and be trouble free.

One of the first SAAB 99s with electronic ignition came in on the hook where I worked. The customer told me he had only changed oil for the last 80,000 miles!

I did an 80,000 mile service and it ran like new. A point type car would have needed a dozen tune ups by then. Which is why Delta Products asked for and got an approval from the CARB.


So how did I get to the point of trying one on my P17?

Well I knew about the Mark Ten from my SAAB experience and I wanted to be able use something like it. Perlux has a 6 volt ignition which fits inside the distributor and they are inexpensive. However they are modern and easy to get.

There's just not enough romance for me in that!  lol

In my research I found a fellow who repairs them and who had a 6 negative ground unit on his shelf. I contacted him and he said he might be able to convert it to 6 volt positive ground. He was a little busy at the time so I'd have to wait. In the mean time I went looking for 3.54 ratio rear axles on eBay (found 4 of them) and in one photo of a car I saw a Mark Ten 6 volt positive ground CDI. I bought it and sent it off to Jim to be repaired/tested. Now I have two! Jim said he'd only seen ONE on eBay in the last 10 years!

The old car hobby is supposed to be FUN.

I can't tell you how much satisfaction I got when the old P17 fired right up and ran so sweetly with the Delta Mark Ten tucked under the hood!





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