![]() The higher the engine speed, the more the cam wants to move. The camshaft has a tendency to move rearward when loaded by the distributor gear. Another good reason has to do with the angled or helical cut of the distributor gear. The most important reason is that the roller tappet can be easily damaged if the cam moves far enough that a lifter might crash into an adjacent lobe. Roller cams also cannot be allowed to move fore or aft in the block for several reasons. ![]() To keep the alignment bar in place, Chevy uses an eight-legged "spider" that places one leg over each of the eight alignment bars in the lifter valley. ![]() Otherwise, the hydraulic part of the lifter operates the same way as a flat-tappet hydraulic tappet. ![]() This requires the lifter to be slightly longer in overall length both for this alignment bar and to create room for the roller. The factory takes care of this by designing two small flat spots on the lifter that accommodate a rectangular alignment bar that slips over a pair of lifters that prevents them from spinning. The most important point about roller lifters is that they must not be allowed to spin in the lifter bore for obvious reasons. ![]()
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