Sorry to hear it man, I feel your pain I lost one on the dyno about a year ago it didnt break anything but burnt the crank and one rod. It happened on the forth dyno pull and was also down about 50 h.p.. I would have been real upset if it hurt my R3 block as they are almost impossible to find. This is also why I dyno all my motors better on the dyno at the engine builders shop than at the track. It got back together and made even more power and torque than what I expected for what the combo is. I hope you find the problem
And build it even stronger and better.