We had a 4840.  Put 10,000 hours on it.  I would take off at full load from and idle.  I have no idea either how.  Part of it has to be that without the turbo it was probably at it's lowest power setting for the displacement.  265 hp out of that beast wasn't pushing it much.  The 8870 that replaced it requires 1500rpm to handle any load at take off.