1972 Mustang with 351w and HEI
I upgrade my distributor to an after market (basically a GM) HEI that has a built-in coil. It has a tach lead which my after market tach work with. I have not swapped out the speedo and dummy lights for a speedo and tach. This OEM tach will not work with the old tach feed from the HEI distributor.
It looks like for ford tach require lead from the coil or tach lead and an igition wire. When we connect the wires to the tach the motor dies.
If I find a wire with 6 to 8 volts on it and replace it for the ignition 12v the tach will work, but it is not accurate.
Does anyone know how to get my OEM tach to work with this after market hei distributor.