Ignition wires for Pertronix III?
12-04-2011, 02:33 PM
#21
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The way I see it is, the positive voltage flow through the coil windings FIRST and THEN to ground through the points set, and when the points open; the break in current flow causes a breakdown in the magnetic field in the PRIMARY (12VDC) coil windings causing the secondary windings to build a charge of several thousand volts (20K to 40K) and then after building up sufficiently enough, the secondary voltage jumps across the spark plug gap in the cylinder. The ignition points would never see a voltage load in excess of the primary output of your alternator (around 13.8-14.2VDC at full battery charge.) I learned this by reading a book on some old grandpa guy named Kettering but, maybe the book was outdated information
As far as finding plug wires Pertronix sells magnetic core 7mm black wires that can be pulled through your Tri-Power's original braided shielding and made to look like OEM but, won't have that needed NCRS date coding in them. Here is the link for them (look to the bottom of the page) Link: http://www.pertronix.com/prod/ig/fla...s/default.aspx
The 7mm Pertronix wiress, Ignitor III and 0.32 Ohm coil work well with the Holley 4 on my wife's 70 LT-1 (with the dummy K-66 box still on the radiator support.) When checking for spark with this set-up I get the god fearing "POP" that I'm used to from MSD and Capacitive Discharge ignitions. That "POP" tells me to watch out or I'll be really sore if I ground it with my fingers if I decide to do a cylinder load test or find the sensor trigger point while replacing the distributor (speaking from previous bad expiriences.)
As far as finding plug wires Pertronix sells magnetic core 7mm black wires that can be pulled through your Tri-Power's original braided shielding and made to look like OEM but, won't have that needed NCRS date coding in them. Here is the link for them (look to the bottom of the page) Link: http://www.pertronix.com/prod/ig/fla...s/default.aspxThe 7mm Pertronix wiress, Ignitor III and 0.32 Ohm coil work well with the Holley 4 on my wife's 70 LT-1 (with the dummy K-66 box still on the radiator support.) When checking for spark with this set-up I get the god fearing "POP" that I'm used to from MSD and Capacitive Discharge ignitions. That "POP" tells me to watch out or I'll be really sore if I ground it with my fingers if I decide to do a cylinder load test or find the sensor trigger point while replacing the distributor (speaking from previous bad expiriences.)
At the point when the primary/secondary voltages stop increasing (ie: the plug arcs over), the secondary (plug) voltage is reflected back to the primary, clamping it (the primary voltage) to the secondary voltage divided by the coil turns ratio. With a typical 20,000 volts at the plug/secondary and a typical coil turns ratio of 100, we arrive at a primary (points or switching transistor) voltage of 200 volts (a bit higher than your alternator setting).
If the primary side of the ignition system only needed to deal with 13.8-14.2 volts, and three or four amps, the system (points or electronic)would be nearly bulletproof. But, dealing with primary flyback voltages of hundreds of volts, it's easy to burn the points or blow up the switching transistor unless there are additional protective devices (the points condenser, or switching transistor clamping zeners) attached to these switching devices.
Last edited by 69427; 12-05-2011 at 12:18 AM. Reason: Grammar correction.
12-05-2011, 10:26 PM
#22
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DRC, how did the install go? I am working on mine. I was trying to keep all the old wires nice and tidy, but wanted to use the grommet on the bottom of the distributor. It looks like there is barely room for the one existing wire, so I cannot see how to squeeze in the additional 2 Pertronix wires in the grommet. Any suggestions what works best? I figure I can take the old wire out, but then no using the points as a backup. Surely cannot leave that wire flapping around in the distributor.
Any good ideas?
Thanks!
