1942 - 1947 Chevrolet Shop Manual



6-53

Tighten all manifold bolts, valve rocker shaft support bolts and nuts. Valve stems should be lubricated with light engine oil to make sure they are not sticking—this is important. Intake valve clearance should be adjusted to a minimum of .006" to a maximum of .008" hot. Exhaust valve clearance should be adjusted to a minimum of .013" to a maximum of .015" hot. Regular attention will practically eliminate cooling system troubles. The most logical times for cleaning and reconditioning the cooling system are: 1. When anti-freeze is installed in the fall. 2. When anti-freeze is removed in the spring. CLUTCH CONSTRUCTION The clutch on all passenger car and trucks is the single plate dry disc type, designed around a diaphragm spring having the shape of a dished		engaged, the fingers are flat and the entire rim of the diaphragm spring exerts pressure against the
		SPRING PIVOTS ON THIS PIVOT RING

		Fig. 110—Engaged Position of Diaphragm Spring pressure plate, Fig. 110. When the clutch pedal is depressed, pressure of the throwout bearing on the inner ends of the fingers causes a diaphragm action and the outer ends of the fingers, near the rim, pivot on the inner pivot ring. Fig. 111. This action
		THROWOUT BEARING FORCES SPRING IN THIS DIRECTION


		Fig. 111—Disengaged Position of Diaphragm Spring causes the rim of the spring and the pressure plate to move back away from the clutch disc, disengaging the clutch. When the clutch pedal is released and the throwout bearing no longer contacts the fingers, the "spring" in this material causes the fingers to pivot about the rear pivot ring and the rim to bear against the pressure plate. Clutch Noises A rattling noise in the clutch assembly at idling speed with the clutch released may be caused by insufficient tension on the pressure plate retracting springs. This noise can be easily remedied by replacing the retracting springs as follows: 1. Remove the clutch housing under-pan. 2. Hand-crank the engine until one retracting spring attaching bolt is at the bottom. Remove the bolt and retracting spring and install a new spring. 3. Replace the other retracting springs in the same manner as described above. Should the above not correct the rattle, the clearance between the drive lugs on the pressure plate and the slots in the clutch cover should be checked. If this clearance exceeds .010", the pressure plate and/or cover assembly should be replaced, to obtain proper clearance.
Fig. 108—Layout of Clutch Parts washer with eighteen tapering fingers pointing inward. Fig. 108. The
spring is made from very high quality steel, carefully heat-treated and shot-blasted to assure long life. The action of the diaphragm spring may be compared to the flexing action of the bottom of an ordinary oil can. By depressing the clutch pedal, the throwout bearing is forced against the diaphragm spring fingers, causing the diaphragm spring to pivot on the pivot rings, Fig. 109 When the clutch is	Fig. 109—Action of Diaphragm Spring