Getting the shine on the crankshaft of 5.3 Liter V8 EcoTec3 engine requires automated microfinishing and electronic measurement to get crank tolerances to the width of a human red blood cell, or within eight microns.

GM uses a micropolishing process on its EcoTec3 V8 crankshaft that whittles the tolerance down to the width of a human blood cell. That’s about eight microns for those you who don’t own a micrometer set that small. A micron, by the way, is 1/1000th of a millimeter or 0.000039 of an inch.

“There are good reasons behind this polishing,” says Anthony Lewandowski, manufacturing engineer at GM’s Tonawanda Engine where the new LT series is built. “When a truck’s tachometer says that its engine is comfortably cruising at 3,600 rpm, that means a crankshaft is revolving 60 times each second inside its bearings on a thin coating of oil.

GM’s 5.3-liter EcoTec3 V8 engine is available in Chevy and GMC pickups and SUVs.

“Micropolishing the crank’s journals improves this oil film’s consistency to reduce friction and improve the EcoTec3’s reliability and durability over the life of the truck,” adds Lewandowski.

Even when the finishing process looks perfect to the naked eye, GM says the micropolishing operation applies 80-micron finishing tape to the journals, rotating back and forth until electronic measuring sensors sign off on that step. The journals may look like steel mirrors at that point, but a second step with an even finer polishing tape is needed before the journals meet design tolerances.

According to GM, even slight temperature changes in the plant can affect the sensors, so they are retested and recalibrated when necessary to ensure accuracy for the 900 crankshafts turned out each day for the 5.3-liter EcoTec3, which is found in the Chevy and GMC pickup trucks and SUVs.