High rpm stresses on the bottom end are usually the worst at the top of the exhaust stroke. The piston wants to continue upward while the crank is just starting back down. The rod, rod bolts and wrist pin are in tremendous tension at this point (as is the wrist pin boss on the piston, but this is rarely the first failure point). Its worst on the exhaust stroke because there is no attendant gas pressure (as on the compression stroke) to help slow the piston. This tension is a function of of the piston speed and the rpm. Both are important because the deceleration of the piston is where the highest stresses are. Its usually the rod beam, or the rod bolts that fail first on Honda engines, although it isn't _always_ that way.
We've generally found that most Honda engines are capable of handling 400-500 rpm over stock on a regular basis for street driving. However, there are prices to pay. On the regular F20C, exceeding 9000 rpm on any regular basis will cause valve retainer problems (as we've seen on some race cars which were never taken above 9300 rpm and no overrevs). But the bottom end is fine. On K20A2 engines, cars that exceed 8600 rpm under racing conditions will break a rod within a couple of races - we've seen it happen to three separate race teams such that it has become a defacto standard to keep stock rod K-motors under 8500 rpm for racing purposes.
