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A spark tester that forces the spark to jump a calibrated (or adjustable) gap is close enough to a peak-voltage reading. My preference is the non-adjustable kind, calibrated for HEI.Used a spark tester - acknowledge that only gives me a visual signal and not a voltage reading.
Kinda guessing that this is more air/fuel related than ignition, but that'd be an excellent way to rule out ignition issues. Worthwhile. Provides more info than just "peak" voltage.I know someone with an ignition oscilloscope who will probably be thrilled to put it to work.
On a Vortec 5.7L?Did you ever find the issue? I've since done some research that mentioned something about the timing being out of phase