1989-2018 Cummins Performance Main Bearings
These H and HX Clevite bearings were developed primarily for use in NASCAR type racing but are suitable for all types of competition engines.
H series bearings have a medium level of eccentricity, high crush and rod bearings have a hardened steel back and thin overlay. These bearings also have enlarged chamfers for greater crankshaft fillet clearance and are made without flash plating for better seating.
The HX series bearings have and .001” extra clearance
The biggest benefit of coated bearings is preventing damage during cold starts and events where oil starvation is evident. Starting your car is almost the worst thing you can do as the oil has had time to drain out of the engine back into the pan. The oil is cold and thicker and takes time to get circulated throughout the engine, including to the crank bearings. The added dry film lubricant coating acts as a barrier between the bearing surface and the crank journal. Other benefits are less friction and longer bearing and crank journal life. The special coating also has moly and other ingredients that retain oil rather than repel it.
This coating process was developed for and is used in race engines, and applied to street and daily-use cars to help yield more durable engines.