Roller hydraulic lifters are used to reduce the amount of friction between the valve lifter and the camshaft lobe. See Figure 2-6. A requirement with the use of a roller lifter is a positive guide device to insure the roller will track consistently. First; the line of action of lifter motion is offset from the camshaft center line, to reduce the skewing motion of the lifter during the cam opening and closing. Second, a lifter guide plate is used, to restrain lifter motion to less than two degrees about its axis. A guide plate clamp holds 2 of the guide plates in position. The clamp is a self-contained bolt attached to a bracket. And there are 4 lifters and 2 guide plates to every guide plate clamp. 1982-1983 guide plates are stamped steel. 1984 and later guide plates are sintered iron.
It is important that the lifter guide plates and retaining brackets are properly installed to prevent lifter rotation; so it is suggested that after installing the guide plates and retainers, to rotate the crankshaft by hand 720° which will cycle the camshaft 360° or one full revolution. Make sure while doing this, that the lifters move up and down in the guide plate. If the engine will not turn over by hand, then one of the lifters is not free to move up & down in the guide plate.