899912021 Mercury TAPPET, (3.418)

Illustration 1 g00514913
Refer to Guideline For Reusable Parts, SEBF8049, "Pistons". Refer to Guideline For Reusable Parts, SEBF8068, "Cylinder Liners". Refer to Guideline For Reusable Parts, SEBF8051, "Piston Pins And Retaining Rings".The 1U-6431 Piston Ring Groove Gauge is necessary for measuring ring grooves in keystone style pistons. Refer to the instructions that are included with the gauge for the correct use of the gauge. (1) Piston crown assembly (2) Piston skirt (3) Top piston ringThe ring should be installed with the side that is marked "UP-1" or "0" toward the top of the piston. The gap between the ends of the piston ring should be checked while the piston ring is installed in a cylinder liner that has the following bore. ... 137.16 mm (5.4000 inch)There are two types of top rings that are available. The two rings are distinguished by a color code. The gap between the ends of the white striped ring is the following dimension. ... 0.55 0.15 mm (.022 .006 inch) The gap between the ends of the yellow striped ring is the following dimension. ... 0.724 0.190 mm (.0285 .0075 inch) (4) Intermediate ringThe ring should be installed with the side that is marked "UP-2" toward the top of the piston. The ends of the piston ring should have the following gap between the ends, when the ring is installed in a cylinder liner that has a bore of 137.16 mm (5.4000 inch). ... 1.080 0.190 mm (.0425 .0075 inch) (5) Oil control ringThe spring ends of the oil control ring should be assembled 180 degrees from the ring end gap. The white colored portion of the spring must be visible at the ring end gap. The width of the groove in the piston for a new oil control ring is the following value. ... 3.210 0.010 mm (.1264 .0004 inch) Thickness of the new oil control ring ... 3.137 0.013 mm (.1235 .0005 inch) Clearance between the groove and the new oil control ring ... 0.073 0.023 mm (.0029 .0009 inch) Maximum permissible clearance (worn) ... 0.15 mm (.006 inch) When the oil control ring is installed in a cylinder liner that has a bore size of 137.16 mm (5.4000 inch), the gap between the ends of the oil control ring should be the following value. ... 0.572 0.190 mm (.0225 .0075 inch)For each 0.03 mm (0.001 inch) increase in the cylinder liner bore size, the clearance between the ends of each of the three piston rings increases by the following value. ... 0.08 mm (.003 inch)Note: The rings should be positioned with the gaps of the rings approximately 120 degrees from each other. (6) Piston pin bore Bore in piston crown bearing for piston pin ... 55.047 0.008 mm (2.1672 .0003 inch) Pin bore diameter in piston skirt ... 55.013 0.004 mm (2.1659 .0002 inch) Diameter of the new piston pin ... 55.000 0.005 mm (2.1654 .0002 inch)