Re: Electronic ignition

Posted by DavidPackard On 2021/7/25 19:01:26
Paul;

I’ve had success with both 12(-), and 6(+) Pertronix ignition systems. The local Model A expert that Ernie and I know is quick to caution about installing a Pertronix ignition module electrically close to an alternator. His advice is to connect the ignition module directly to the battery. I’ve been thinking about that advice for quite a while and the only thing I’ve come-up with is the potential of an AC component in the alternator output, especially if the internal capacitor is weak/fails, and I’m not real sure whether that type of failure is detectable without an oscilloscope. Readers should know that a Model A produces quite a bit of electro-magnetic interference from the secondary side of the ignition system, and the Pertronix system seems to be immune to this type of environment, but I suspect they conduct quite a bit of testing within EMI environments.

The years of service using Pertronix ignition are; 15 years (12-), 8 years (6+), and 5 years (6+), with no known problems, or service needs. The local Model A expert also cautions about coil designs that place a resistor internally. His concern is the resistor will likely be at the bottom of the coil housing, and if the coil is oil filled the resistor may not be cooled if the coil is mounted ‘nose down’ . . . as in the Model A and ‘48-‘54 Packards. I use Pertronix epoxy filled coils that are just about in the middle of the recommended resistance range. Pertronix did say that reliability is a function of coil resistance (within the recommended range), but not enough to be concerned about. This business about coils has nothing to do with whether the ignition is electronic or points, and the guy that specializes in Model A sees a lot of failed parts and tries to spread the word when he runs across a problem.

Pertronix’s recommendation on how to implement the functionality of the overdrive kick-down feature in one of their 6+ units is in the attached file. Seems the 7 ohm circuit will defeat the spark sufficiently, while also limiting the current through the ignition module. Without the resistor the kick-down circuit would essentially ‘short to ground’ the ignition module for whatever the latent time is to have the overdrive solenoid change position. I suspect, but don’t know by how much, that the ignition module’s reliability would suffer with the module shorted to ground.

Paul I think you can install an electronic ignition with a good amount of stealth, however on an Autolite system the Pertronics wires will enter the distributor versus the external connection on the OEM unit. My goal was to install the Pertronics system without altering the stock wire loom, so I mounted a barrier strip to make all of the connections (within reach of the stock loom), and mount the 7 ohm resistor. All of that mess was mounted to the side of the cylinder head hiding under the coil and ignition wires. I agree with Mechagon, the conversion is straightforward, and is not glaring even if you include the constraint of ‘do no harm’. HH56 comment about having almost ‘no room for error’ with a 6 volt starting system is equally correct. I have a NAPA 3EH battery, and soldered AWG 00 cables in my ’48 288, and that combination is acceptable. There are no substitutes for cold cranking amps and circular mils. Paul it’s up to you . . . its 100% reversible if you decide to restore the car to ‘as built’ condition.

dp

Attach file:


pdf pertronix6VPGInstallationInstructions_withOverDrive.pdf Size: 156.18 KB; Hits: 84

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