[CraftEngines]

Primary size somewhat depends on the driving characteristics you are looking for. The larger diameter will make more high rpm power as a smaller diameter will make better low end torque. As far as detonation is concerned, you can make 650hp without that issue. As long as you keep the compression low enough and make up the power in cubic inch, head flow, and camshaft. This of course may hurt the low end drive-ability but it is possible.