My 383 has been acting out of time off and on. I went to check the timing and I noticed an occasional clank coming out of the passenger side of the top of the motor.No real pattern to it, just every now and then and sometimes repeatedly,then have to wait a bit to hear it again. Went to shut it down and the same clank happened on shut down. WTF? Is this a lifter? If so can I just get a new set or should I replace the cam too? Thanks in advance for the help.