mr28

I have a 87 iroc that I changed over to a carb. car an cannot get the tach. to work I have a msd 6 al box an a pro billet dist with a blaster coil on my car I have a white wire that comes from the tach. I hooked it up to the side of the msd box an no go. so I went an bought a msd 8920 tach adpter an still no go. so yesterday I went an pulled the cluster out an there is 1 white that I think it feeds the tach. I really don't know what else to do I taught the last thing to do is splice into that white that comes out of the tach in the dash to the msd box. I also check the power to the con. at the dash where it hooks to the cluster an I have power with key in run pos, I know that D6 is tach wire CAN SOMEONE PLEASE HELP ME THANK YOUS!!!!!!!!!!!!!!