[brainsboy]

In a modified motor the materials used are stronger and often lighter. They turn higher rpms and have more loads placed on them so they need to be stronger. When you tighten a rod bearing cap you have the section between the cap and rod which is a weak point, this weak point creates distortions. These are called static distortions. When the motor is running, you have the weight of the rods, the type of material used, rpm range which creates dynamic distortions. When you deal with racing, not street cars you have lighter pistons, lighter rods, and stronger parts, the distortions seen in race parts is not as great as in a stock vehical. Remember bearings are not round, all bearings are oval in design, A stock rod is going to need more eccentricity then a rod strong enough to handle 2000hp, because the force needed to created distortion is greater in a stronger rod.