Installing main bearing shells
When installing the main bearing shells into the cover, align the protrusion on the shell with the groove in the cover.
Plastigage rod for measuring bearing clearances located on the crankshaft
Measuring the width of a deformed Plastigage rod using a scale ruler
Installing a thrust half ring on the main bearing cap
Installing the main bearing cap
1. Clean the rear of the bearing shell and its installation location in the cylinder block and main bearing caps.
2. Install the inserts in their places, while the protrusion on the insert should be aligned with the groove on the cover.
Information copied from the website: MercedesMan.ru
3. One method, which requires a micrometer to measure the bore diameter, is to install the main bearing caps with the shell on the cylinder block and tighten them to the specified torque. Measure the inside diameter of each assembled pair of bearing shells. Measure the diameter of each crankshaft journal. Subtract the corresponding crankshaft journal diameter from the measured bearing diameter.
4. Second (and more accurate) the method is to use a product known as Plastigage. This is a round plastic rod that is compressed between the bearing shell and the crankshaft journal. After removing the main bearing cap, the deformed plastic rod is measured with a special template that is included with the Plastigage. The procedure for using Plastigage is as follows.
5. Install the crankshaft without lubrication on the liners installed in the cylinder block. The crankshaft journals and liners must be completely clean and dry.
6. Cut a few pieces of Plastigage plastic rod (they should be slightly shorter than the width of the main bearings) and install on each crankshaft journal.
7. Install the caps with the lower liners and tighten the mounting bolts to the specified torque. Do not rotate the crankshaft during the Plastigage clearance measurement.
8. Unscrew the liner mounting cover, remove it and apply a scale ruler to the deformed plastic rod. By comparing the width of the deformed plastic rod with the reference width on the scale ruler, determine the size of the gap.
9. Finally, thoroughly clean away any traces of Plastigage from the bearings and crankshaft.