Top dead center (TDC) of the piston of the first cylinder

Top dead center (TDC) piston is the point through which each piston passes when cranking the crankshaft. Each piston reaches TDC at the end of the compression stroke, and then again at the end of the exhaust stroke. In order to install the engine timing mechanism, the TDC of the piston of the first cylinder is used. On HCS and Endura-E engines, the TDC position of cylinder 1 is determined by the mark on the crankshaft pulley.

Check that the ignition is off Remove the high voltage wires from the spark plugs, then unscrew the spark plugs.

Turn the engine with a wrench, by the crankshaft pulleys, until the alignment mark on the crankshaft pulley aligns with the TDC mark (0) on the cover of the gas distribution mechanism. When approaching the mark on the pulley, at the same time the piston of cylinder No. 1 approaches the top of the cylinder (see figure 2A.2).



You can check that the piston is on the compression stroke by removing the cylinder head cover and observing the movement of the valves.

After aligning the timing marks on the crankshaft pulley and timing cover, rock the crankshaft back and forth a few degrees to each side of this position and observe the valve action for cylinder #1. When the piston of cylinder #1 is at TDC, the intake and exhaust valves of cylinder #1 will be fully closed, but the corresponding valves of cylinder #4 will be in the open and closed positions. If the valves of cylinders 1 and 4 are in opposite positions, it is necessary to turn the crankshaft one full revolution so that the piston of the first cylinder is at TDC on the compression stroke.

After setting the piston of the first cylinder to TDC on the compression stroke, you can set any other piston in series to TDC on the compression stroke by turning the crankshaft clockwise by 180°and taking into account the order of operation of the cylinders.