I know what you are saying, but its basically the stroke. shorter stroke=high rpm, but youll need a rod thats longer, or keep it short and have a very low compression ratio (the skyline has a stroke of somewhere around 72mm, and some skylines can rev to 15k, 9k stock though). A engine with a longer stroke would have greater torque but shorter rods, but that could cause the cylinder walls to flex and limit revs. also what lsvtec said made me relize the effect of a longer stroke. All of this is pretty much based on distance from the center of crank to the top of deck. I didnt relize the effect it would have on compression ratio till i used a cr calculator. i'v tried to figure out the best rod/stroke combo for the b18, it turns out it already comes with the best combo for the b18; 1.58 r/s found in b18c. ive also figured out the BEST ratio for an engine the size of the b18c but, the displacement went to 1.6; the cylinders can be bored to 84mm and there it is, a perfect r/s ratio and 1.8L, but requires custom rods and crank.