CHAPTER 1 THE ENGINE 1 :1 1 :2 1 :3 1 :4 1 :5 1 :6 1 :7 1 :8 1:9 1 :10 1 :11 Description Engine removal (sedan—all versions) Engine removal (station wagon) Engine disassembly (sedan—all versions) Engine disassembly (station wagon ) Cylinder head removal, servicing and replacement Timing gear overhaul Crankcase and cylinders Piston assembly Connecting rods Crankshaft and main bearings 1 :1 Description The 'New 500' two-cylinder aircooled engine operates on the four-stroke 'Otto Cycle' and is fitted directly to the transmission unit which incorporates the rear drive assembly as shown in FIG 1 :1 and FIG 1 :2. With the power unit fitted at the rear several advantages are obtained including better load distribution to the wheels when the vehicle is loaded, elimination of propeller shaft reducing the size of centre tunnel and better use of available space. The cylinder block comprises two cast iron cylinder barrels with cooling fins. The bottom of the cylinders fit into machined seats in the aluminium crankcase. The aluminium crankcase carries eight studs on which are located the two cylinder barrels with the aluminium cylinder head on the top. A two bush crankshaft of special cast iron is fitted into the lower half of the crankcase. The crankshaft is F500 provided with a counterweight and is hollow to allow for lubrication. The steel connecting rods have thin wall bearing halves on the big-end, and bronze bushes in the small-end. The offset piston pin is of steel and retained in the piston by two circlips. Light alloy pistons are used and are of the taper-oval- shaped type with a maximum diameter at the base of the skirt, along an axis perpendicular to the piston pin. Pistons are fitted with four rings as follows, one compression at the top, two standard oil scraper rings and one side slotted oil scraper ring. The one-piece aluminium cylinder head is finned to provide a larger cooling surface and carries the inlet and exhaust manifolds. The inlet passages merge into a single centralized flange onto which is mounted the carburetter. The exhaust passages run almost parallel to the axis of the engine.