One or two thousandths of an inch extra doesn't sound like much, but it can mean the difference between life and death for your engine bearings. We're talking about the effect bearing clearance has on engine life and power. Too much bearing clearance creates problems because all the oil that's pumping in to fill the gap between the bearings lowers engine oil pressure. This excess oil is then thrown off the crank, creating windage, which robs power and generally decreases engine performance. Years of research have been devoted to improving bearing technology, but there are still some inexperienced engine builders who run very loose bearing clearances thinking it will make power.

0.0025 IS THE KEY

Callies Performance has studied the effects bearing clearance has on oil temperature, flow, and load capacity with an emphasis on how reductions in clearance affect the life and performance of the bearings. Callies research has shown that a bearing clearance between 0.0020 and 0.0025 inch is ideal in almost all street and race applications. Although the difference between these two dimensions is small, there is much to be gained or lost if bearing clearance deviates far from it. Bearing clearance between 0.0020 and 0.0025 inch is the best compromise between high bearing load capacities and low bearing temperatures. The three graphs on the previous pages represent what Callies research determined. CHP

Callies Performance Products
Federal-Mogul Corp. (Speed-Pro)