I've done upgrades to the ignition system and now I'm trying to figure out a tach. My question is are the RPM'S measured by each combustion on the face of each side of the rotor or is it measured by each time, let's say face #1 makes 1 full rotation?

79SA 12A manual transmission, no longer points.

Thanks for reading.

 

tach gets it's signal from the + terminal of the trailing coil. if u upgraded form points dist to electronic dist, nothing changes in relation to the tach.

 

I changed the whole setup completely.
83 dizzy MSD6A control box with 3 MSD epoxy filled high vibration coils. Two direct fire to the leading ones and one that fire's into the dizzy on the leading side and out to both trailing from the leading side.
MSD6A is setup to fire as a 6CYL. I don't get the correct RPM reading from the coils. I'm working on designing a setup to get the correct RPM signal which is why I was wondering if the RPM'S are measured by each combustion cycle from each face or if it's measured by each time one face makes a complete rotation.

 

stock tach is signaled off the trailing coil. connecting there should read correctly.