what could be the problem?
 

I have a 97 F150 with a 4.6. It was running a little rough and started to misfire in cylinder 7. I replaced my plugs and wires and from the looks of the old it was well needed. As soon as i started the engine i hear a loud knocking coming from around the number 7 cylinder. I had no warning signs and other than the plugs and wires going bad it ran great before. I know it could possibly be a loose rocker arm, bent push rod, or a bent valve...Does anybody know if there is any way to tell what it is without digging too far into the engine. Time is a factor its my only means of transportation and as soon as I get a rounded bolt out Ill have my valve cover off to check the push rods and rocker arms.