Talking to a few operators that have run both 420 and 470 12litre engines they find the 470s a lot heavier on fuel,in fact folklore has it that a chipped 420 is the way to go.
Talking to a few operators that have run both 420 and 470 12litre engines they find the 470s a lot heavier on fuel,in fact folklore has it that a chipped 420 is the way to go.