[89IROC&RS]

well what you get into there is the relation of bore on intake charge velocities and bore/stroke ratios and such. the simple explenation is that the smaller bore longer stroke creates high low rpm port velocities makeing good low end power, but as rpms increase, piston speed increases quite substantially which is hard on the rotating assembly, and also moves too fast to make proper use of the intake charge. so top end power is reduced. the small bore blocks are pretty much for truck engines.

disclaimer - this is a generalization, of course small bore blocks can be made into performance engines, but for the general description, they are truck engines.