What Ron is trying to explain is that basically connecting rod length plays a role in how the engine will behave. Let's look at the model 21 engine. Ever noticed why the intake is short with a larger i.d. than the 31/33? And why the combustion chamber so shrouded? Then answer is a shorter rod. A short rod will pull massive amounts of air into the engine, but not expel it very easily. Hence a larger induction system to lower port velocity. The combustion chamber is heavily shrouded for the same reason. Though valve curtain area is poor, you will still have moderately good swirl, and all the gases are 'funneled' to the exhaust valve. But this can be fixed. Enter rod ratio. By lengthening the connecting rod, you can find the desired balance between intake and exhaust events, i.e., appropriate flow through the cylinder head, not just one side of the head. Design engineers like to say a rod ratio anywhere from 1.2-1.8:1 is best. And here's where it will get costly, if you do not use the currently available off-the-shelf parts. Changing rod length means changing piston compression height. There IS a limit. Piston speed and the angles between crankshaft to connecting rod, and connecting rod to piston are all factors that must be considered. And bigger is not always better, as you will find with broken skirts and crankpins.