So I pulled the distributor cap and rotor to inspect and clean the inside, receptacles, check terminals etc. Did seem to have some scale on the terminals. Cleaned up real good though and reinstalled. Putting it back together I measured a couple different coil wires. About 1' long, one wire comes out to 9300 ohms, the other 500 ohms. Didn't expect that. Which one do I want to use? Ignition system is Ford points distributor, cap and rotor, Pertronix Ignitor and 1.5 ohm Flamethrower coil with full time battery voltage, spiral coil resistance plug wires and brand new NGK non-resistor plugs gapped at .030". Using my superior skills of deductive reasoning (ha ha) I figured the resistance wire should give a hotter spark. So then, I tried the different coil wires back and forth and it seems a little harder to start and didn't seem to sound right at idle with the high resistance wire. The 500 ohm coil wire, engine then started immediately idles noticeably faster and smoother. So left that one in. What's up with that? Is this just my imagination. The high resistance coil wire is fairly old, but is within spec afaik.
Resistance in high tension leads has a huge range, depending on wire type and brand. Here's from the MSD site: MSD’s 8.5mm Super Conductor Wire will measure about 50-ohms per foot of wire while the Street Fire brand wires have about 500 ohms per foot. But the old "rule of thumb" from back in the points days was 6,000 ohms resistance per foot. This was for the radio suppression rated wire.
Right, but let's argue, for the moment anyway, that we aren't concerned at all about RFI. Neighborhood cell phone, radio, and television reception has collapsed, QSL cards are coming in from around the world, garage doors all over are opening up and down, guys with heart pacemakers clutching their chest in pain as I drive by etc etc. Never mind that stuff. Do solid core or low resistance wires mean a hotter spark? Seems to me a wire could degrade spark energy, never improve it. I think maybe what happened here, the 9.3k ohm wire is toast, it's pretty dang old. The plug wires themselves are new or nearly so, spiral resistance type, but maybe a solid core copper coil wire or Packard wire would be the way to go. It doesn't wear out anyway. Some of the ignition guys (who sell wires.... hm) say the coil wire should be replaced often.
First of all, different wire manufacturers will have different specs (resistance wise) as well, some manufacturers will have different specs for a number of different wires they produce. A comparison from one to the other is going to net you different results and maybe not the best way to determine if a wire is good or bad. Many years ago when carbon core resistor wire was relatively new I would use a rule of thumb that any wire with over 20,000 ohms resistance was no longer serviceable. With some of the wire available today I'd want to know the specs on the wire I was testing before coming to any conclusion. Part of the equation is also the insulating capability of the wire. A wire that is in spec resistance wise but not able to keep the high voltage on route to where it needs to go is no good to anybody. So, resistance too high or able to leak high voltage to ground before it reaches it's destination are both reasons to replace a wire. Any wire that looks old enough to be suspected of being old is probably in the last stages of useful life and maybe should be replaced. My 2 cents.
Resistance wire used for radio suppression has a resistance of 5000 ohms per foot, more or less. I don't know about the newest types but that was the rule from the fifties to the eighties at least. You should be able to look up the specs on the manufacturer's web site. The longer wire may be defective, it should not have that much resistance for 1 foot.
That could be, maybe it's defective and the resistance has doubled from whatever the original spec was. No way to know really. I thought the engineering claims though, were that resistance wires increased the spark intensity, on account of the fact that the coil reaches a higher value before it will fire the plug. I suppose that's not the case if a wire is defective, as it appears with my 10k ohm wire. If we're not concerned about radio reception, will solid core wires increase spark intensity compared with suppression type wires and plugs? I guess I thought they were a magneto only thing.
The Jalopy Journal
