By the time a knock louder than a rattle develops, the crankshaft is usually trashed. Be sure and measure all the rod journals- - - -more than a thousandth or so out of round or score marks you can hang a fingernail into means the crank needs to be reground or replaced. Try rolling the engine over by hand with all the spark plugs removed- - - -you might have a piece of debris on top of a piston that's hammering against the cylinder head. One knocking engine I worked on had swallowed a screw from the carburetor air horn and it was imbedded in the top of a piston.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!