<VV> Re: main jet vs idle and spark plug miss

[Frank DuVal]

Dan Timberlake writes:
"And ignition components subjected to multiple full power hi-pot tests with plug lead yank-offs.  I provide Genuine grounding, Especially on fragile vintage European electronic ignitions, but even on points ignitions,"

I would not hi-pot test an electronic ignition system, but have removed spark plug leads from many a distributor on points systems to troubleshoot. The old  adage works here: "if it fails, it was bad anyway".  Pulling the plug wire out of a running distributor should be done with knowledge of where the spark will jump to and how it will hurt you! But, it provides another piece of the troubleshooting puzzle: If a cylinder starts running better when the plug wire is pulled out 1/8" to 1/4", just to where the spark is heard clearly, then the spark plug is firing with  higher voltage. Hence the hi-pot terminology of running without  the plug lead connected. If higher voltage make the cylinder fire, but not fire with normal voltage then you could be firing a leaner mixture and therefore a fuel system lean condition due to carb problems or vacuum leaks. You should swap out the wire and plug to eliminate them as suspects as high resistance wire may also need higher voltage, or a fouled plug. Many 2 stroke engines that fouled out can be run with the plug lead pulled out slightly. Also, if you are old enough you can remember the snake oil salesmen with the gadget that they inserted in series with the center tower on the distributor and coil lead. The engine was run with out the device and a tachometer showed a certain RPM. They then inserted the device and the tachometer showed more RPM. Hucksters I tell you. It was nothing more than a spark gap to provide a higher voltage spark at idle. Maybe they leaned out the mixture to get such a change for their demo. I saw it demonstrated on a Pontiac straight 8 flathead back about 1960. J.C. Whitney also had them for sale....

I have also heard more cylinder compression needs more spark plug voltage. Hence the better coils on the Spyders.

So Padgett, does the #6 plug wire making the engine run better for a second occur when the plug lead is close enough to jump the spark gap?

Frank DuVal