spark plug arcing

Hello i hope every buddy is having a great Halloween. ok i hope somebody can help me. ok i notice a week ago that i had spark plug arcing so i change the spark plug cables (msd) and spark plugs ( autolites)hoping that will fix the problem well it didnt i still had the same problem so i exchange the cables thinking that they mite me be defective so installed the new ones and i still had the same problem dos anybody have an idea of what can be going wrong....could it be the spark plug gap size cause when i installed them i didnt check them because the guy at pepboys told me that they where gaped already?

well it arcing from the spark plug boot into the engine block where the spark plugs go in. i have used 2 sets of msd cables and its still arcing from the same area