Cylinder Head Cam Tower Shim Set .075" 240Z 260Z 280Z 280ZXCamshaft mount shim set for Datsun 240Z, 260Z, 280Z and 280ZX, 1970 1983. These shims are . 075" thickness. Cam tower shims are needed if you mill the cylinder head surface a significant amount so that the timing chain has too much slack in it and the camshaft needs to be raised. These shims fit under the camshaft mounts. These shims can be used when milling the head up to . 080" for increased compression and to retain original camshaft height.