LO 8-12 Identify and describe the purpose, types, composition, and failures of plain split insert bearings

Bearing Location

Bearings must not move within the bearing bore and must have good contact within the bore for good heat transfer. Several construction features of a bearing are common to ensure these functions. One feature is the use of locating lugs on bearings to prevent movement and to properly center the bearing in the bore Figure 81. To ensure correct matching of bearing caps and lugs, bearing caps are assembled together with lugs located tab against tab. Make sure that the identification numbers match for the main bearing location in the block and on the connecting rod bearings. Another construction feature is called bearing spread . To assist bearing retention and good contact with the cap or web of the bearing bore for heat transfer, the parting face of a bearing is made wider than the diameter of the cap or web. Bearings, having a spread feature, must be snapped or pushed into place Figure 82.

FIGURE 08-81: A lug fits into a notch in the bearing cap or bearing bore to center the bearing and prevent its movement.

FIGURE 08-82: The concepts of bearing crush and spread. Bearings must seat tightly into the bearing bore to prevent movement and transfer heat.

Bearing crush is another construction feature that helps locate a bearing where it will be kept from moving and transferring heat. The diameter of both bearing shells is larger than the bearing bore; the difference in height between the bearing and the cap or web is called bearing crush . When assembled, the protruding section of parting halves of the bearing inserts above the bearing cap are forced against one another, crushing or forcing the bearing tightly into its bore. Dark spots observed on the back of a bearing indicate where the greatest heat transfer takes place in a crushed bearing. For this reason, bearings should go in dry on the backside with no grease or thread locking liquid applied to the back of the shell. Using this material would insulate the transfer of heat from the bearing.