I have come to the realization that the idea is too Kooky to be practical. I would have gladly run an electronic distributor and coil, just for the purposes of triggering a tach signal.
I'm building a dedicated race truck that will see very few miles.
The Ford (or equivalent) magnetic sensor looks like a pretty solid idea.
The optical sensor measuring at the cam sprocket seems OK, too.
Right now, I'm seriously thinking about buying one of those digital tiny tachs.
Steve.
i dont like having the sensor that close to my timing belt. ive already had one sensor come apart on me, i dont want it to be able to come apart, and break my timing belt..
getting the reading directly from the crank with an external sensor is a little less prone to failure, if you ask me.."
my crank trigger tach idea was based off the photo-electric tach.. but highly modified..
all i had to do, was tach 2 nuts on my crank pulley, build a bracket for the sensor, and run wiring..
plus, you can use this method to drive almost any gasser 4 cylinder tach..