1942 - 1947 Chevrolet Shop Manual



	*6-28*

	The grinding wheel on the valve refacing machine should be properly dressed to make sure it is true and smooth. The valve stem is then clamped in the chuck of the machine and the chuck set at a 30 degree angle. The beveled face of the valve head is then passed across the face of	CAUTION—The cylinder head gasket must be installed with the side marked "This side up" on top, Fig. 63, so all water passage holes and cylinder head bolt holes will line up properly.


		Fig. 63-Cylinder Head Gasket To properly align the cylinder head to the cylinder block and keep the cylinder head gasket in place to prevent damage, the two cylinder head guide pins should be used. They screw into the cylinder block at the front and rear holes on the manifold side and guide the head into position. After the head has been properly aligned, insert and tighten the cylinder head bolts with a wrench, tightening each one evenly a little at a time in the order shown in the cylinder head bolt tightening diagram, Fig. 64. The order or sequence in which

	Fig. 62—Valve Refacing Machine the grinding wheel until this surface is true and smooth all around the valve. Care should be taken while grinding not to remove too much stock from the face of the valve. This is important to prevent burning of valves in operation. For quiet operation, it is important that the end of each valve stem be free from pits. The valve should be placed in the "V" block on the refacing machine, and the end of the valve stem ground until it is true and smooth. To test for perfect valve and seat contact, mark lines with a lead pencil about 1/4" apart on the face of the valve and replace the valve in the head. Give the valve one-half turn to the right and one-half turn to the left, using a little extra pressure on the valve. If all pencil marks are removed, as a result of the face contacting the seat, the grinding is perfect. If, on the other hand, one line or part of one remains untouched, this indicates an uneven spot, and the valve must be refaced until it seats properly. Before replacing the valves in the cylinder head, clean the valves and the cylinder head. A good valve job is frequently ruined by failure to properly clean all of the parts, INSTALLING CYLINDER HEAD ASSEMBLY The best practice is to install a new cylinder head gasket each time the cylinder head is removed and reassembled to the block.
		Fig. 64—Cylinder Head Bolt Tightening Diagram the bolts are tightened is important, since many water leaks between cylinders are caused by improper tightening of cylinder head bolts. When a tension wrench is used to secure uniform tension on all bolts, the recommended tension is from 75 to 80 foot pounds. VALVE ADJUSTMENT PROCEDURE Before adjusting the valve-stem-to-rocker-arm clearance, it is extremely important that the engine be thoroughly warmed up to normalize the expansion of all parts and stabilize the oil temperature. This is very important because during the warm-up period, the valve clearance will change considerably. To adjust the valves during this warm-up period will produce clearances far from correct after the engine reaches normal operating temperature.