37678 Mercury SPRING, TENSION - CHOKE ROD

Illustration 1 g01411623
(A) Piston diameterEach piston has markings (1) which are stamped on top of the piston. The markings are used to align the piston assembly to the camshaft side of the cylinder block.Table 2 gives the dimensions for pistons that are standard. Table 2 also gives the dimensions for pistons that are oversize.Note: Measure the piston diameter along the perpendicular of the piston pin bore.
Table 1
Dimensions for Piston Diameters    
Bore Size     Standard at Assembly     Service Limit (1)    
Standard     101.915 to 101.945 mm (4.0124 to 4.0136 inch)    
101.730 mm (4.0051 inch)    
Oversize
0.25 mm (0.010 inch)    
102.165 to 102.195 mm (4.0222 to 4.0234 inch)    
101.980 mm (4.0150 inch)    
Oversize
0.50 mm (0.020 inch)    
102.415 to 102.445 mm (4.0321 to 4.0333 inch)    
102.230 mm (4.0248 inch)    
( 1 ) A piston which exceeds this limit must be replaced.
Illustration 2 g01411629
(B) Diameter of piston pin bore (C) Diameter of piston pin ... 33.993 to 34.000 mm (1.3383 to 1.3386 inch)Measure the piston pin bore diameter. Subtract the piston pin diameter from the bore diameter. The clearance between the bore and piston pin ... 0.002 to 0.019 mm (0.0001 to 0.0007 inch)Note: The service limit for the clearance between the piston pin and the piston pin bore is 0.050 mm (0.0020 inch). Replace the piston if the clearance has been exceeded.
Illustration 3 g01411644
(3) Install the piston rings with the identification mark toward the top.Note: Each piston ring is marked with an "R" or "T" for an identification mark. (4) When the top piston ring is installed in a cylinder liner with a bore of 102 mm (4.0 inch), the clearance between the ends of the top piston ring is the following distance. ... 0.30 to 0.45 mm (0.012 to 0.018 inch)Note: Replace the top piston rings if the end gap exceeds the maximum tolerance of 1.50 mm (0.060 inch). (5) When the intermediate piston ring is installed in a cylinder liner with a bore size of 102 mm (4.0 inch), the clearance between the ends of the intermediate piston ring is the following distance. ... 0.30 to 0.45 mm (0.012 to 0.018 inch)Note: Replace the intermediate piston rings if the end gap exceeds the maximum tolerance of 1.50 mm (0.060 inch).Note: The position of the end gap of the oil control ring is 180 degrees from the ends of the ring expander. (6) When the oil control piston ring is installed in a cylinder liner with a bore of 102 mm (4.0 inch), the clearance between the ends of the oil control piston ring is the following distance. ... 0.30 to 0.50 mm (0.012 to 0.020 inch)Note: Replace the oil control piston rings if the end gap exceeds the maximum tolerance of 1.50 mm (0.060 inch).
Illustration 4 g01411650
Note: Install new piston rings in the ring grooves of the piston. Measure the side clearance of the ring groove (D) with a straight edge and feeler gauge. Table 3 gives acceptable clearances of the ring groove.
Table 2
Clearances of the Piston Rings    
Piston Rings     Width of Ring     Side Clearance of Ring Groove     Service Limit (2)    
No. 1 Compression Ring    
3.00 mm (0.118 inch)    
0.080 to 0.120 mm (0.0031 to 0.0047 inch)    
0.200 mm (0.0079 inch)    
No. 2 Compression Ring    
2.00 mm (0.079 inch)    
0.080 to 0.120 mm (0.0031 to 0.0047 inch)    
0.150 mm (0.0060 inch)    
Oil Control Ring    
4.00 mm (0.157 inch)    
0.025 to 0.065 mm (0.0010 to 0.0026 inch)    
0.150 mm (0.0060 inch)    
( 2 ) The piston must be replaced if the piston rings exceed these clearances.
Illustration 5 g01411654
(8) Camshaft side of engine block (9) End gap for no. 1 ring (top compression ring) (10) End gap for no. 2 ring (intermediate compression ring) (11) End gap for oil control ring (12) Side of engine with combustion chamberNote: Position the piston rings according to Illustration 5.