Camshaft thrust button bolt. Stops camshaft from moving back and forth in engine, giving perfect valve timing and greater timing chain life. Includes new cam bolt and bronze button. Fits all 64-84 except diesel. DMR-5120 cam spacer is required and DMR-5040 crank spacer is recommended. If necessary, file the front of the cam bolt (not the bronze button) to achieve .004 to .005 clearance (end play) from the front cover. Does not include DMR-5120 cam spacer nor DMR-5040 crank spacer. For complete kit see DMR-5745.