Charon
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694 cc represents about a 6.5% increase over the basic 652 cc. Stroke stays the same, so rpm limits stay about the same. Torque is generally about proportional to displacement; horsepower is the product of torque and (unchanged) speed. Thus I would expect about 6.5% increase in torque and power. If compression increases due to different piston configuration, torque should increase a little more. The tradeoff is the need for premium fuel. If there is no change in the head or the valves, the larger displacement might result in slightly decreased high-rpm breathing efficiency, which may reduce the torque gain, but it might possibly give a little better bottom-end torque.
If I were seriously contemplating such a change, I would want to make a series of careful measurements, specifically including a dyno run, before I started. I would then want to repeat the measurements after the modifications, to see whether I had actually gained anything. Without real before-and-after measurements, you will never really know whether you did anything.
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