Here is a quick way to check for a loose timing gear that is causing a knock. With the engine running slowly, screw out timing pin, located in timing gear cover, and insert opposite end of pin into opening (see Fig. 850). Care must be used not to let your hand come in contact with the fan.

Press in firmly on Pin; if the knock stops, the trouble is undoubtedly due to the gear being loose on the camshaft. .

To lessen any possibility of the gear be- coming loose on the shaft, the thread limits on the camshaft and camshaft nut were reduced some time ago. Also a special lock washer A-6260 is being used in partial production.

If an instance is brought to your attention of a cam gear loosening on the shaft, install washer A-6260 and Heighten the camshaft nut. This will hold the gear securely in place.