I have done the volume test with my old pump and the results are:
2.6 Liters per 30 seconds so 82.44 GPH or 312 LPH
Note:this is at 0 PSI this is simply the transfer ability of the pump, for a horsepower calculator to be accurate, it would have to have this volume at 75-100 psi. I am assuming that it can support 75 PSI with this volume.
From various calculators this is more than enough for 420 crank horsepower, actually calculators say 700-750 hp possible.