Tru Power Engine Kit. 4-Cylinder Gas, 172 CID, 3.9 inch Standard Bore. Engine Overhaul Kit. Contains sleeves, pistons, rings, pins & retainers, pin bushings, complete gasket set, intake & exhaust valves, springs, guides, valve keys,standard rod and main bearings . For 800, 801, 900, 901, 4000 Tractors (1963-1964).