Aluminum Bearings

Clevite’s Bob Anderson is among the many in the aftermarket industry who agrees that two-layer aluminum bearings work, but prefers three layer Babbit overlay shells in most applications. “A bimetal aluminum bearing is a compromise, just like any bearing is. You want something strong enough to support the loads you’re putting on it. You also want something that’s somewhat embeddable, so that dirt or debris ends up in the bearing instead of tearing up the crank. And if you have any misalignment you want something that’s somewhat forgiving, so that hopefully it will move some material around rather than score a crankshaft or seize the engine. It should also have (good) thermal conductivity and have a certain amount of surface action, so that if it does come into contact with the shaft, it won’t seize or lock up the shaft. A bimetal aluminum bearing can do the job, but we feel that a trimetal bearing offers the least amount of compromises especially in the aftermarket. You don’t have the control over tolerances that the OE installation does. A trimetal copper-lead bearing can handle loads in the area of 12,000 plus PSI. The best you can get with a bimetal aluminum bearing is 6-7000 PSI.” Anderson also notes that the Babbit overlay makes three layer designs much more tolerant of assembly and production variations in crank journals. Which should you choose? Consider the O.E. fit and general engine condition before going either way, and remember that the installation procedure is all-important to good bearing service. As Anderson says simply: “The best rule of thumb, especially when you have the pan off is: keep it all clean and straight.”

ALUMINUM BEARINGS