Surely hearing the motor could give an indicator of whether it might be nosing over, or a possible engine problem.
I know it looks a little antiquated but it's cheaper than spending a fortune on a playback tach.
Mick


69 Dart GTS 440 mopar .590 cam, Edelbrock heads, 3200#
best et 6.45, 106.78, 10.14, 132.88 mph, 1.47 60ft
best 60ft 1.36