They aren't lightweight engines, but the amount of power that Cummins in particular are getting out of common-rail diesels is amazing- from the factory, their 5.9 liter QSB marine engine makes better than 500 hp and probably over 800 ft-lbs of torque...this is well over 100hp/liter which is pretty good in anyone's book. I don't know how long they hold together. And all that out of 360 cubic inches...