The RB30 had harmonics issues over 7500rpm. It's been awhile since I did all my research on the motor, so I don't recall (offhand) whether or not it was an issue with the crank, crank girdle, or rods. Trying to make an RB30 rev past that point may be prohibitively expensive. Like James mentioned, though, 99% of street drivers will never need to rev the motor to, or beyond, this point.