Typical steel-backed lead babbit cam bearings do an excellent job in everyday use but have a number of shortcomings in severe-duty applications. First, in many engine designs, oil is routed from the oil pump to the cam, then to the main bearings, and then to the rod bearings, in that order. In a highly stressed mill, it should be the other way around. The rotating assembly spins twice as fast as the cam and is much more heavily loaded than the cam journals.
Second, whenever radical cam profiles are used, so too are high-pressure valvesprings. As they maintain order within the valvetrain, stiff springs also create plenty of extra friction between the lifters and cam lobes. This is transferred directly to the cam bearings where accelerated wear can result.
Finally, there is the issue of oil temperature. We all know that petroleum-based motor oil can break down if things get too hot. Eliminating much of the friction caused by the spinning cam yields a measurable decrease in oil temperature for added longevity and safety.
All three potential problems are eliminated when you switch to rollerized cam bearings. It eliminates the oil flow leakage around the cam bearings, providing full volume to the rotating assembly, and the superior construction of the roller bearings will handle up to 900 pounds of valve-open spring pressure without problems. (Numbers over 1,000 pounds can be tricky, but you’ll never go there unless you’re fielding a Pro Stocker.) The reduced friction can drop oil temperature by as much as 20 degrees, allowing dry sump users to carry and pump less oil.
Are rollerized cam bearings for you? If your motor lives life one quarter-mile at a time, probably not. The block machine work, cam bearing kit, and specific camshaft can cost upward of $700. You could spend the money more effectively elsewhere. But if you stay on it for miles on end, roller cam bearings are a definite engine-saver. Typical users include Bonneville racers, Silver State entrants who run WFOT for 90 miles, and Sprint Car racers who run balls-out for 30 laps. We’d be remiss if we didn’t mention the end-all endurance crazies of NASCAR. Every last one of them relies on rollerized cam bearings. In this story, Gene Ohly and Jaime Gonzalez of Evans Speed show us the right way to enjoy the benefits of rollerization.
