1942 - 1947 Chevrolet Shop Manual



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	Carefully remove all particles of carbon from the ring grooves in the piston, and inspect the grooves carefully for burrs or nicks that might cause the rings to hang up. Slip the outer surface of the ring into the piston ring groove and roll the ring entirely around the groove to make sure that the ring is free and does not bind in the groove at any point, Fig. 7. If binding occurs the cause should be determined and removed by careful dressing with a fine-cut file. However, if the binding is caused by a distorted ring, install a new ring. Proper clearance of the piston ring in its piston ring groove is very important in maintaining engine performance and in preventing excessive oil consumption. Therefore, when fitting new rings, the following clearances between the top and bottom surfaces and the ring grooves should be provided: The two compression rings should be fitted so that a .0015" feeler gauge will be free, but a .003" feeler will cause a rather heavy drag. At the bottom, or oil control groove, a .002" feeler should be free but a .0035" feeler should produce a heavy drag. It is important that each ring be fitted to its individual cylinder for gap spacing and its individual piston and groove for clearances. A final test of the ring fit in the grooves is to repeat the fitting procedure given above after the rings are assembled in the grooves of the pistons, Fig. 8.	chamfer on the bottom of the inserter must fit into the chamfer at the top of the cylinder.

		Fig. 9—Inserting Piston in Cylinder Bore MAIN BEARINGS Chevrolet main bearings are steel back babbitt-lined. The babbitt is centrifugally cast or "spun-in" into the steel lining. This method assures a positive bond between the steel and the babbitt and also prevents the formation of air pockets in the babbitt metal. The advantage of this type bearing is that the rate of expansion is similar to that of the parts with which they come in contact. This prevents loosening of the bearings. The thin wall of the bearing permits it to conform to both the crankshaft and the bearing bore in the cylinder block, assuring a snug fit at all times. Both of these important features of Chevrolet main bearings insure long life.


	Fig. 8—Checking Piston Ring Clearance in Ring Groove In slipping the pistons back into the cylinders, use extreme care and do not force the rings into the bore. Compress the rings with the piston inserter as shown in Fig. 9, until they enter the cylinder freely. In using this piston inserter the
		Fig. 10—Main Bearing Boring Machine When necessary to replace main bearings, the clutch housing should not be removed from the cylinder block. This is very important, as the transmission pilot hole in the clutch housing is used in aligning the boring bar. Should it be