Race Built motor. Fully balanced. AGU crank (used but crack tested before build) either very unlucky, or other suggested potential contributor is the use of non mass damped crank pulley.. (neuspeed in this case) - resonant/harmonics possible contributor. all speculation from the carnage however. Engine revved to 9krpm, on solid lifters. not @ time of failure tho. 590bhp (peak) but not @ time of failure, lower boost being run at the time Owch.. Feel very sorry for my friend/owner of this engine.