1942 - 1947 Chevrolet Shop Manual



	6-27

	Place the grinder over the expanding pilot, then loosen the Allen set screw "B," Fig. 58, and push down the adjusting rod "C" against the top of the pilot. Then lock the set screw "B" tightly.	into the valve seat by turning the feed screw "E" to the left one notch at a time until the wheel is grinding all around the face of the valve seat. Before shutting off the grinder, stop feeding the wheel into the valve seat and give it time to grind itself free. Turn off the switch and allow the grinder to stop before lifting it from the pilot. Mount the valve seat dial indicator on the pilot, set at zero and turn the sleeve of the indicator with thumb and finger. When the seat is properly ground, the indicator reading will be within .001", Fig. 60. The valve seats should now be narrowed down to the proper width which is 3/64" to 1/16" for the intake valve seats and 1/16" to 3/32" for exhaust valve seats. This operation is done by machining both the port and the top of the valve seat. A 70-degree grinding wheel should be used in the intake and exhaust ports, and a 20-degree grinding wheel to thin down the exhaust seats from the top. A form cutter, KMO-105-7, must be used to thin down the intake valve scats from the top, Fig. 61. This tool, at the same time, machines the edge of


	Fig. 59—Grinding Intake Valve Seat in Head Turn the feed screw "E," Fig. 59, to the right until the grinding wheel just clears the seat. Balance the grinder with the compensating handle "F." Start the motor and feed the grinding wheel

		Fig. 41—Using Cutter to Narrow Intake Valve Seat the valve recess in the head, thereby smoothing this passage for the free flow of the incoming gases. Good judgment must be used when narrowing a valve seat to make sure the seat contacts the center of the valve face. This is very important because the life of a valve reconditioning job depends to a great extent upon the width of the valve seat and point of seat contact with the valve face. If the valve seat in the head is too narrow, heat will not be dissipated from the valve head fast enough. If too wide, carbon particles can be readily caught between the valve face and seat, causing the valve to hold open and blowby, which will soon burn both the valve and the seat in the head. Refacing Valves Valves that are pitted can be refaced to the proper angle, insuring correct relation between the head and stem, on a valve refacing machine illustrated in Fig. 62.
	Fig. 60—Checking Valve Seat with Indicator