User is correct about boreing, only done for rebuilds, not power. 331's and 347's are .030 over bore too. a 302 has a 3" stroke, 331--3.25" stroke, and 347--3.4" stroke. 331/347 usually utilize a 5.4" rod where 302 use a 5.095 I believe. The stroke does not effect the crank stregth. However...