Clevite MS1625P Engine Bearing

Clevite Main BearingsMain Bearings SetVarious forms of main bearing grooving have been used over theyears. We are frequently asked what difference grooving makes.First, its essential to understand that bearings rely on afilm of oil to keep them separated from the shaft surface. This oilfilm is developed by shaft rotation. As the shaft spins it pullssoil into the loaded bearing area and rides up on this filmmuch like a tire hydroplaning on wet pavement. Grooving in abearing acts like tread on a tire to break up the oil film. Whileyou want your tires to grip the road, you don't want your bearingsto grip the shaft.The main reason to have any grooving in a main bearing isto provide oil to the connecting rods. Without rod bearings tofeed, a simple oil hole would be sufficient to lubricate the mainbearing. Many early engines used full grooved bearings and someeven use multiple grooves. As engine and bearing technologydeveloped, grooving was eliminated from modern mainbearings and lower bearings. The result is a thicker oil film for the toride shaft. This provides a greater margin of safety and improved bearinglife. Upper main shells, which see lower loads than the reduced ones, have retained a groove to supply theconnecting rods with oil.In an effort to develop the best possible main bearing designsfor performance engines, weve investigated the effects of mainbearing grooving on bearing performance. The graphs on the nextpage illustrate that a simple 180 groove in the top of the main shellis still the best overall design. While a slightly shorter 140 groove offers a marginalgain, the majority of the benefit is to the top of the shell, which doesnt needimprovement. On the other hand, extending the groove in the lowerhalf, even as little as 20 in each metal line (220 in total), takes away from superior bearing performance without providing anybenefit to the lower half.