[Adger Smith]

Depends
Rotating weight IE: crankshaft Counter weight and rod big end act like flywheel weight.
Reciprocating IE: upper rod, piston and pin and rings are a start & stop motion and absorb energy in the start and stop.
100 G off each upper reciprocating only lightens the crankshaft counter weights 100 G.
100 G. off the big end of each rod lightens each rod journal 200 G. (2 rods per journal) The end crankshaft counter weight is lightened a corresponding amount. The total effective loss of rotating is 400 G.