Measuring Bearing Clearance
When the engine speed increases so does the piston weight, which is pulling harder on the connecting rod and pinching the bearing at the parting line. Now all bearings are made with eccentricity built into them, which means these bearings have more clearance at the parting line, especially high performance bearings used at high RPM’s. Bearing clearance will be measured at the tightest point (in line with the wrist pin end of the rod). This is the measurement you will most likely record. You should also measure the clearance at the parting line. Ideally, you want three times more clearance here. For example, if you have .002” to .0025” at the tightest point, you should try to have .007” to .0075” at the parting line. As engine RPM increases so does the clearance at the tightest gap and the clearance t the parting line begins to shrink.
