Can I use a modern timing light to test my engine if I have a 6-volt electrical system?


     The label on the timing light pertains ONLY to the power supply 
used to operate the light. If you power it from a separate 12 volt 
battery, it will work just fine on your 6 volt car. There will be three 
leads on the device: the red one goes to the + terminal of the 12 volt 
battery, the black one goes to the - terminal of the 12 volt battery, 
and the third one goes to the spark plug wire for #1 cylinder (the 
driver's side front). Your 55 is a positive ground car, so you may find 
that the timing light will work better if you add one additional wire from 
the + terminal of the car's 6 volt battery to the + terminal of the 12 volt 
battery. You can first try it without this wire, but if the light flash 
seems weak, then add the additional wire. You should take pains that there 
is no metal to metal contact from the timing light or the battery terminals 
to anything else. Other than grabbing the spark plug wire while the engine 
is running, there is no way you can get a jolt off the wires, so don't be 
timid about hooking it up. I   use my timing light this way all the time.