I got reminded, by Roger Garnett, that if you have a current-sensing
tach, as opposed to impulse counting, it will have to be mucked with
if you switch to an electronic ignition. My Allison draws so much
more current that the tach reads about 50% high. I've been told by
a tech guy at Allison that you can modify the tach to read correctly
again. He suggested removing one of the coils in the tach to reduce
the sensitivity, then use the adjusting screw to get it right on
using an external clip-on tach as reference. I think that what I'll
do to get the sensitivity down is parallel the tach with a resistor
whose value I'll determine experimentally; that way I'll have less
resistance imposed by the tach being in-line with the ignition system.
Note that it's possible to make your own resistor of a very low value
by using a length of small-guage or resistance wire cut to length.
-me
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