Joe, I used the "Crane" photo optical systems for many years on many engines. My first was on a Rotary project for myself to which we were going for well over 10K RPM's with two plugs per chamber firing just a few degrees apart on the same "burn stroke". Lots of other stuff too and never a failure, but racing we kept things fresh! I ran the one I modified for the A-4 for over 20 years and replaced it only for the "LED" indicator. Kept the Alison for a spare, same plug and I could zip-tie it in place. Not as fast as the switch for sure
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Dave Neptune