The question came up at work:  Does the timing light flash as the current passes through the inductive pick up or does it flash as the current jumps to ground via the spark plug?  We set timing at WOT at 6000 rpm fully loaded on the dyno.  We set individual cylinders to read the same as cylinder #1.  We adjust this timing by bending the reluctor inside the distributor for any cylinders that are differant.  The question arises because as the cylinder pressure increases the resistance across the spark plug increases, thus slowing the actual ignition timing and perhaps delaying the signal to the timing light?  Any thoughts?

The timing light is triggered by the spark current that is also jumping the gap at that instant.

Conversely, if there's an ECU in the circuit between the reluctor and the spark coil, then all sorts of strange behaviors are possible, including retard of an individual cylinder in response to ...butterflyvalves well, anything that the ECU can sense or infer.

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