Engine Assembly

Valve Lifters and Push Rods

Genuine Chevrolet valve lifters are made from castings. The head of the lifter is chilled during the casting operation, giving a hard wearing surface to the bottom of the lifter. After the casting has been made, the lifter is machined and accurately ground, being held to very close limits. The inspection operations are very rigid and only those parts that pass this inspection are used in production and service.

The push rods are made from a solid piece of steel with the two ends upset. The ends of the push rod are carefully machined to give a smooth surface at the points where the rod contacts the valve lifter and the rocker arm.
In assembling the valve lifter to the engine, it should be a free fit, and the end that contacts the camshaft should be smooth. If this end shows any signs of wear, it is good practice to replace these parts.
The push rods are assembled to the engine in two groups of six each in the following manner. Thread the push rod through the spring retainer and assemble the push rod spring to the end of the rod, holding it in place with the retainer key. Fig. 70. These assemblies are then placed in the engine, being sure that the push rods are seated in the bottom of the valve lifters, and the spring retainer securely bolted in position.
Fig. 70— Push Rod Springs
Valve Springs
Genuine Chevrolet valve springs are made from a special analysis steel wire. They are accurately coiled, and, after being made, each spring is checked to be sure that it comes within the limits for tension. Any springs that fail to pass this inspection are immediately scrapped.
For quiet operation, it is important that the end of the valve stem be free from pits. The valve should be placed in the "V" block, on the facing machine, and the end of the valve stem ground until it is true and smooth.
After the valve has been properly faced, smear grinding compound thinly on the beveled edge of the valve head. Place a light coil spring 1 % inches long around the valve stem and then insert the valve in its original position.
Fig. 69— Valve Refacing Machine
The valve should then be turned back and forth through a quarter turn, using enough pressure to overcome the resistance of the spring. The valve should not be turned through a complete circle, as this would cause the compound to cut ridges on the surfaces.
After rotating the valve a few moments, release the pressure on the valve. This will cause the coil spring to act, lifting the valve slightly. Before again turning the valve, turn it one-quarter revolution. Add fresh grinding compound when necessary.
Continue the grinding operation until the entire contact surfaces of both the valve and the cylinder head seats show a complete seat not less than is and not more than 332" wide.
To test for perfect contact, mark lines with a lead pencil about %" apart on the beveled edge of the valve head and replace the valve.
Give the valve one-half turn to the right and one-half turn to the left, using a little extra pressure on the valve. I f all pencil marks are removed, the grinding is perfect. If, on the other hand, one sline or part of one remains untouched, this fact indicates an uneven spot, and the valve must be reground until it seats properly.
Before replacing the valves in the cylinder head, clean all grinding compound from the valves and the cylinder head. A good valve job is frequently ruined by failure to properly clean all of the parts,

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