Installing the main bearing shells
When installing the main bearing shells in the cap, align the protrusion on the bushing with the groove in the cap.
Plastigage rod for measuring bearing clearances located on the crankshaft
Measuring the width of a deformed Plastigage bar using a scale bar
Installing the thrust half ring on the main bearing cap
Installing the main bearing cap
1. Clean the back of the bushing and its mounting location in the cylinder block and main bearing caps.
2. Install the earbuds into place, making sure that the tab on the earbud aligns with the groove on the cover.
3. One method, which involves having a micrometer to measure the diameter of the bores, is to install the main bearing caps along with the bushing on the cylinder block and screw them to the required torque. Measure the inside diameter of each assembled pair of bearing shells. Measure the diameter of each crankshaft main journal. Subtract from the measured bearing diameter the corresponding diameter of the crankshaft main journal.
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 bushing and the crankshaft journal. After removing the main bearing cap, the deformed plastic rod is measured with a special gauge, which is included in the Plastigage kit. The procedure for using Plastigage is as follows.
5. On the liners installed in the cylinder block, install the crankshaft without lubrication. The crankshaft journals and liners must be perfectly clean and dry.
6. Cut off a few pieces of the plastic Plastigage rod (they should be slightly shorter than the width of the main bearings) and install on each crankshaft journal.
7. Install the covers with the bottom liners and tighten the mounting bolts to the required torque. Do not rotate the crankshaft while measuring clearance with the Plastigage method.
8. Unscrew the cover of the insert attachment, remove it and attach a scale ruler to the deformed plastic rod. By comparing the width of the deformed plastic rod with the reference width on the scale bar, determine the amount of gap.
9. Finally, carefully clean the traces of Plastigage - the material from the liners and the crankshaft.