Needed: Digital circuit to monitor rpm and advance

[Chris Adam Thomas]

I'm looking for a circuit to measure rpm and instantaneous ign advance
accurately.  I have an old analog circuit/device for this but the accuracy
isn't adequate. { It must be really nice to have a dyno and equipment and 
not have to improvise and do the tweaking on the road :-)  }  

Thanks for the help

cat   nasa at suns.chinalake.navy.mil