If you feed them off a 12v automotive battery and get around 800 rpm, they will be around 14v/1000rpm (13.9mV/rpm).
If you do not have the torque constant value, you could make an educated guess from comparable motor sizes from other manuf, then using a moment arm off the shaft and a spring scale on the other end, slowly increase the armature current until the estimated constant Torque value is achieved (Nm or In-lbs) and measure the current at this value.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.