I don't think it was runaway. It was just one of those engines doing what they do. The stuff they do to those engines borders on insane. Solid billet blocks, massive turbo pressures and massive amounts of fuel. They essentially have to light them off in stages or the engine will choke out. Not uncommon to see them melting down a set of brake pads in the rear to put enough load on the engine to get enough exhaust pressure to spool the massive turbos. Its all a bit crazy. Not something I would want to do, but makes for entertaining videos.
3000+ HP is usually the target they shoot for....and lots of them grenade.
" We had just crossed 2200HP at 146psi when the 6.7L Cummins block simply couldn't handle the pressure and separated! We have done over 3000HP on this longblock setup so we feel like it was definitely a premature failure, but we see no signs of a problem in the datalog, pistons or rods before the block split. It looks as though the failure was simply stress fatigue to the OEM Cummins Block. The Longblock had been Modified by D&J Precision Machine with a Deckplate, 1" longer rods, ductile Iron Sleeves and 9/16" head studs, main studs and custom girdle, all which held up to the abuse had the block not failed. D&J has a new billet block in production stages that will hopefully prove to increase block strength significantly. "