30667 Mercruiser STUD, (.250-20/.250-28 x 3.125), FLAME ARRESTOR

Illustration 1 g01377415Note: Refer to the appropriate Reuse and Salvage Guideline for information on the pistons, the piston pins, and the retaining rings.Note: Lubricate the piston body assembly with clean engine oil around the zone (A) and the top of the piston body assembly prior to assembly into the cylinder block.Top Piston Ring
The 1U-6431 Piston Ring Groove Gauge Gp is used for measuring the ring grooves in keystone style pistons. Refer to the Special Instruction that is supplied with the piston ring groove gauge. (1) Top piston ring Install the top piston ring with "UP-1" mark toward the top of the piston.There is a clearance between the ends of the top piston ring. When the top piston ring is installed in a cylinder liner with a bore of 137.16 mm (5.400 inch), the clearance is the following value. ... 0.55 0.15 mm (0.022 0.006 inch)There is an increase in the clearance between the ends of the top piston rings for each 0.030 mm (0.0012 inch) increase in the cylinder liner bore. Increase ... 0.08 mm (0.003 inch)Intermediate Piston Ring
The 1U-6431 Piston Ring Groove Gauge Gp is used for measuring the ring grooves in keystone style pistons. Refer to the Special Instruction that is supplied with the piston ring groove gauge. (2) Intermediate piston ring Install the intermediate piston ring with "UP-2" mark toward the top of the piston.There is a clearance between the ends of the intermediate piston ring. When the piston ring is installed in a cylinder liner with a bore of 137.16 mm (5.400 inch), the clearance is the following value. ... 1.080 0.190 mm (0.0425 0.0075 inch)There is an increase in the clearance between the ends of the piston rings for each 0.030 mm (0.0012 inch) increase in the cylinder liner bore. Increase ... 0.08 mm (0.003 inch)Oil Control Piston Ring
(3) Oil control piston ring Note: The spring ends of the oil control piston ring should be assembled 180 degrees from the ring end gap.The 5P-3519 Piston Ring Groove Gauge Gp is available for checking the ring grooves with straight sides. Refer to the Guideline for Reusable Parts for instructions on using the piston ring groove gauge.Width of groove in new piston for oil control piston ring ... 3.190 0.010 mm (0.1256 0.0004 inch)Thickness of new oil control piston ring ... 3.137 0.013 mm (0.1235 0.0005 inch)There is a clearance between the ends of the oil control piston ring. When the oil control piston ring is installed in a cylinder liner with a bore of 137.16 mm (5.400 inch), the clearance is the following value. ... 0.57 0.19 mm (0.022 0.008 inch)There is an increase in the clearance between the ends of the oil control piston rings for each 0.030 mm (0.0012 inch) increase in the cylinder liner bore. Increase ... 0.08 mm (0.003 inch)Piston Pin
Note: Lubricate the piston pin with clean engine oil before assembly. (4) Piston pin Diameter of the bore in the piston for the piston pin ... 50.815 0.005 mm (2.0000 0.0002 inch)Diameter of the new piston pin ... 50.795 0.005 mm (1.9998 0.0002 inch)