tach signal

I have a 454 tbi engine.The coil is a little different from what i am used to.It has two plugs on top with two wires running from each of the plugs.One is red and the other is white.I cant figure out for the life of me what i am doing wrong.first off i am using the power from the dc plug.with the wires coming from the dc plug that i have hooked in i hook the red wire from the tach to the hot on the plug and the black wire to the ground on the plug.Than i hook the green wire to the white wire coming from the coil.I am not certain but i think at this point should start to see a reaction from the tach.It does nothing on either white wire side on the coil.I am pretty sure that one of these white wires have to be the the tach signal but not sure now.