| Consider that the strength of the block comes from the integrity of the casting and the cylinders provide a substantial amount of this strength because they extend from the deck surface to the bottom of the crankcase tying everything together internally. The block is the foundation of the entire assembly in which its stability will allow more power to be made all by itself – compromising its strength for the sake of a 10% increase in displacement is just a poor trade-off. The cylinder’s rigidity not only contributes to overall block strength but also to piston ring-seal, a thin cylinder wall will not maintain its shape even under “normal” combustion pressure, leading to a massive blow-by situation… and how much boost do you want to run? Lastly, head gaskets… over-boring the cylinder reduces the clamping area that the head gasket has with the block. I guess you could hope that this is the weakest link in the system because the alternative is crappy performance or a windowed block.
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