* * * * i hope that this ans has helped.
on the distrubutor where it says tach
The instructions will come with the new tach.
on my tach, the green wire connects to the neg on the ign coil pack
Connect the green wire to the negative side of the coil.
the green is the signal wire and it goes to the negative side of the ignition coil
In order to install a tachometer on your 1987 Monte Carlo SS, you must first find the tachometer wire by using an automotive diagnostic tool. Mount the tachometer on the dashboard. Connect green, red, black, and white wires to the distributor, ignition power, cigarette lighter, and headlights, respectively. Turn on the engine to test if the tachometer works.
There are two connections, the one labeled TD connect to the TD output of ignition control box (a junction connection is on fender) and the other connect to a power source.
pin 48 on the pcm connecter is tach signal connect to your green wire from tach
Remove the instrument panel cover. Remove the tachometer retaining screws. Remove the tachometer cable from the back of the tachometer. Reverse the process to install the new tachometer.
To install a tachometer first determine where the tachometer will be mounted on the dash column. Then, use a flathead screwdriver to tighten the clamp around the column of the tachometer mount. Next, put the two red "trigger" wires through the firewall and connect the other ends to the coil wires of the distributor. Wrap the tachometer wire around the ignition coil bolts. The remaining two wires must be wired into the ignition of the car. Insert them into the power terminal of the fuse box which permits the tachometer to operate when the engine is on.
One white goes to the negative side of the coil and the other to ground.