mini starter problems

I just replaced my mini starter on my 440 10 5 1 compression with one from 440 source I have started it about ten times in the last month and at first it seem ok. Now if i go to start it seems like the starter is grinding i check the bolts and they are tight. I was wondering if a bad ground would cause this. I have a ground runnin from the k frame to the motor. The battery is located in the trunk. I have the neg cable grounded to the trunk floor which is alluimin. I was wondering if that would be the problem. I am going to change it and run it to the frame rail.