timing chain hitting the china covers can hit around the front seal can hit around the top of cover . timming chain can hit some block if a double row roller chain . the PCV valve can make any were from a buzzing sound to a dry bearing noise . the base plate of the carb could be loose and many other thing as well. bolts to long in the fly wheel /flex plate hitting the back of block . the damper rubbing on front tin or timming tab . mechanical fuel pump going south ? front pump bearing in trans or converter thurst washer . bendix drive on starter no coming all the way out of the fly wheel