> There have been so many excellent guesses. I tried to check this one out
> by placing an ohm meter across the insulator areas that would get
> contaminated by this sort of thing but there was no reading.
> Here is another clue: When the plugs have been really bad, I can place a
> timing light on the ignition wires and it will blink intermittently. In
> addition to that when it would flash, I would also hear an extra pop
> from the tail pipe as if it were firing on that cylinder. My current set
> of plugs are not so bad where I can do this measurement yet but I did do
> this in the past. What would cause intermittent flashing on a timing
> light? An open or a short? Also I noticed this affect was on the #3 and
> #4 plugs, right in the center of the engine.
> >Here is a guess. I have read that some fuel additives will cause near
> >invisible deposits on the spark plug insulators. Some of these can be
> >electrically conductive. Perhaps using to much lead substitute?
> >Greg Gelhar
Greg, I'm wondering if it's a spark plug issue. New spark plugs may be so
efficient, that your problem may not be observable, but as they wear, the
problem can be seen. Something else, which will get worse, could be the
culprit. I once had a shaky distributor rotor that kept ruining the carbon
filament on the distributor cap. I'm wondering if your electrical
connections inside the distributor cap are clean?
'59 TR3A (Body off, rest refurbrished, replaced, and back on!)