72 Tach issue with HEI

[brandnew72]

Just rewired the truck, everything works except the tach. Drives great, all things functioning. The distributor cap has a Batt and TACH terminal. Ignition to BATT and the green wire from the tach itself hooks to the Tach terminal. No rpm displayed. Tach lights up, needle goes through it's preset motions and then displays 0 rpm.

Has a signal filter, just installed, still nothing. Glowshift gauge, set to cylinder setting 8.

Should their be varying voltage on the Tach terminal if read with a multimeter? Just trying to narrow it down because it seems so simple but doesnt function correctly. The wires can only go so many places.