810776A 1 Mercury MEMORY PISTON ASSEMBLY

Length of The Connecting Rod
The connecting rod length (CRL) is the length of the connecting rod. Refer to Table 1 for each grade of length of connecting rod.In order to ensure that the piston height above the cylinder block is correct, three grades of connecting rods "R" to "B" are used during manufacture at the factory. Replacement connecting rods are available in three grades. These grades of connecting rod are "R" to "B". The grade of length is identified by a letter or a color which is marked on the side of the connecting rod. The longest grade is marked with the letter "R". The shortest grade is marked with the letter "B". The difference in length between each grade of connecting rods is the following value: 0.076 mm (0.0030 inch)The grade of length of a connecting rod is determined in the factory by machining an eccentric hole in a semi-finished piston pin bushing. Therefore, the grade of length is determined by the position of the center of the hole in the piston pin bearing. If the connecting rod must be replaced, a new connecting rod assembly must be purchased and installed. Refer to Table 1 for more information. A new piston pin bearing is installed in the new connecting rod at the factory. The bore of the piston pin bearing is reamed to the correct eccentricity.Piston Pin Bearings
Note: This procedure requires personnel with the correct training and the use of specialized equipment for machining.If the piston pin bearing requires replacement but the original connecting rod is not replaced, the following procedures must be performed:
Determine the grade of length of the connecting rod. Use one of the following characteristics:
The mark
The color
Measuring the length
Ensure that the connecting rod is aligned parallel and that the connecting rod is not distorted. Refer to "Distortion of The Connecting Rod" in this service module.
Remove the piston pin bearing from the connecting rod. Install a new bearing in the connecting rod. The new bearing is partially finished. The new bearing must be bored off-center to the correct diameter. This off-center position is determined by the grade of length of the connecting rod. Refer to Table 1. The correct diameter of the bore in the piston pin bearing is given in Specifications , "Connecting Rod". Surface finish of the bored hole in the piston pin bearing ... Ra 0.8 micrometers
Machine the ends of the piston pin bearing to the correct length. Remove any sharp edges. Refer to Specifications, "Connecting Rod".
If the grade of length of the connecting rod is changed, the letter that is stamped on the connecting rod must be removed. Etch a letter that is for the new grade of length on the side of the connecting rod. Note: Do not stamp a new letter on the connecting rod. The force of stamping may damage the connecting rod.Table 1 references the following information: Grade of letter of the connecting rod, the color code of the connecting rods and the lengths of the connecting rods.
Table 1
Length Grades for Connecting Rods
Grade Letter Color Code Length Of The Connecting Rod (CRL)
R Red 161.259 to 161.292 mm (6.3488 to 6.3501 inch)
G Green 161.183 to 161.216 mm (6.3458 to 6.3471 inch)
B Blue 161.107 to 161.140 mm (6.3428 to 6.3441 inch) Measure The Length Of The Connecting Rod
If the mark or the color of the grade of length cannot be observed on the connecting rod, perform the following procedure:
Illustration 1 g00326546
Measure the length of the connecting rod.
(1) Measuring pins
(2) Connecting rod
(CRL) Connecting Rod Length
Refer to Illustration 1. Use the following tools in order to measure the length of the connecting rod:
Appropriate gauges for measuring distance
Measuring pins (1)
Ensure that the measuring pins (1) are parallel. "CRL" is measured when the bearing for the crankshaft journal is removed and the original piston pin bearing is installed. Measure "CRL". Compare the "CRL" that is given in Table 1. The grade of length of the connecting rod is determined by the "CRL". Refer to Table 1 for the correct grade of length.Distortion of The Connecting Rod
Use the following tools in order to measure the distances for the connecting rod (2) which are specified in Illustration 1:
Appropriate gauges for measuring distance
Measuring pins (1)
Illustration 2 g00326423
Measure the connecting rod for distortion.
(1) Measuring pins
(2) Connecting rod
(L) The length between the centers of the piston pin bearing and the crankshaft journal bearing is shown in Illustration 2.
Measure the connecting rod for distortion and parallel alignment between the bores. The bores for the crankshaft bearing and the bearing for the piston pin must be square and parallel with each other within the required limits. If the piston pin bearing is removed, the limit "L" is the following value: 0.25 mm ( 0.010 inch)The limits are measured at a distance of 127 mm (5.0 inch) from each side of the connecting rod. If the piston pin bearing is not removed, the limit "L" is the following value: 0.06 mm ( 0.0024 inch)L is equal to 219.08 0.03 mm (8.625 0.001 inch).
Inspect the piston pin bearing and the piston pin for wear.
Measure the clearance of the piston pin in the piston pin bearing. Refer to the Specifications, "Connecting Rod" for dimensions.