Internal combustion engine

An improved internal combustion engine, comprising a fuel System, a cylinder, said cylinder including a cylinder liner portion and a cylinder head, said cylinder head including cooling passage therein, said cylinder head being cooled by a single fluid, a piston movable within said cylinder, the outer portion of said cylinder comprising an upper, a middle and a lower portion, cooling fins positioned on the middle portion only, the clearance between the piston and the cylinder liner being an amount which allows adequate cooling of the cylinder liner, engine lubricating oil, and piston solely by natural convection, said clearance being uniform around the confronting circumference of said piston and cylinder, said fuel system comprising a fuel source, a fuel injection pump, an injection nozzle mounted in the cylinder head, a first fuel line means extending between the pump and the fuel injection nozzle, and a second fuel line means providing fluid communication among the fuel source, said cooling passages, and said fuel injection pump for said fuel prior to its being supplied to said first fuel line means, whereby the fuel acts as a coolant to cool the cylinder head.