Re: what happens to MPG with larger heads?
Hey-Since your motor has a set amount of cubic inches per motor...the new heads withe same carburator will stay the same+/-. The heads will allow you to flow better with a larger carburator and a larger cam...but then you are adding to a higher overall RPM maximum for your HP and torque(defeating the purpose of a 4x4 rock crawling axle snapping low RPM beast)...with the larger valves it will take longer to reach the motors volumetric effecientcy because there will be a increase of volumetric effecientcy also, because you are increasing the airflow to the motor and it will be easier on the motor because it will not have to rev higher to reach the V.E. but will surpass its 'past' HP/torque ratings and continue to climb to its new peaks..do you got that?...hope this helps...so no your MPG should stay the same, but you do have a larger window now to 'hot rod' your motor...
MARK (OIIIIO) LANGMOTORSPORTS