BY ROY BERNDT, ENGINE REBUILDER
DECEMBER 2005

The term ?crush? refers to the outward force created by the portion of the bearing, which extends above the housing bore when the bearing halves are set into place. This ?extra? material holds the outside diameter of the bearings firmly against the housing bore when the assembly is torqued to specification, By increasing the surface contact between the bearing and connecting rod housing bore, crush minimizes bearing movement, helps to compensate for bore distortion and aids in heat transfer.

In simple terms: bearing crush is what holds the bearing in place. The tang or locator tab on the shell that fits the saddle is only for locating the bearing during assembly.

?Eccentricity? refers to the variation in the inside diameter of a bearing assembly when it is measured at different points around its bore. A properly designed engine bearing is not truly round when it is installed in the connecting rod or engine block.

Under operating loads, a rod or main housing bore will distort, pulling inward at the parting line between the upper and lower halves. To keep the bearing from contacting the crankshaft in these areas, most designs include additional clearance at each parting end of the bearing. As engine loads increase, so does the amount of distortion, thus race and heavy duty bearings will require greater eccentricity than do passenger car bearings.

Chrysler 4.7L and 3.7L engines have transitioned to the ?no tab? rod bearings but the part numbers have stayed the same. The ?no tab? bearing is the service replacement as well as new production for these engines. The aftermarket has followed suit with the ?no tab? bearing update, so everyone needs to get a grip and realize that the locator tab may be a thing of the past.

If you are wondering why these bearings and connecting rods have been changed, there?s a simple explanation: it?s less expensive to manufacture a bearing and connecting rod without a tab. You may actually find yourself in a position of having to install both types in the same engine because of inventory depletion of the early style tang type bearings. Fear not: it?s no big thing and the engine will never know the difference.

Special Thanks to the engineering staffs of both Clevite and Federal-Mogul Corporation for their contributions to the column.