Sidecar Flip
Living Legend
Maybe....
I'm zip on that one. Could be combustion noise. Alloy cased engines have certain resonant qualities that cast iron don't exhibit. Iron castings, nodular or not, exhibit sound deadening qualities. Aluminum pressure castings do not.
Remember, there is a large amount of noise generated inside. You can't hear it because the sound waves produced by combustion very quickly come up against the mass of the sleeves, water jacket and the alloy block but they are still there and they do cause resonance which may be interpreted as a rod knock.
I'm zip on that one. Could be combustion noise. Alloy cased engines have certain resonant qualities that cast iron don't exhibit. Iron castings, nodular or not, exhibit sound deadening qualities. Aluminum pressure castings do not.
Remember, there is a large amount of noise generated inside. You can't hear it because the sound waves produced by combustion very quickly come up against the mass of the sleeves, water jacket and the alloy block but they are still there and they do cause resonance which may be interpreted as a rod knock.