TECHNOLOGY REPORT PROPULSION GM puts its new 2023 Corvette V8 on a different 'plane' LT2 V8's stroke to create a more powerful - and more exotically vocal - 5.5-L V8, internally coded LT6. What's old is new again The 'rough period' Kettering called out was vibration at a frequency equivalent to twice crankshaft speed - secondorder vibration. Despite Cadillac's practice of carefully weighing and balancing pistons and connecting rods and counterweighting its crankshafts, the shakes common to four-cylinder engines persisted when the cylinder count was doubled in a flat-plane-crank V8. As a result, cross-plane-crank V8s have enjoyed broad acclaim over the last century of use. Examples of contemporary cross-plane (GM LT4 on left) and flat-plane (Ford 5.2L) V8 crankshafts showing arrangements of crank throws. Cadillac didn't invent the V8 engine, but GM's premium brand deserves credit for advancing that prime mover's cause over the past century. One of the most significant strides came in 1923 in response to GM Research Laboratories head Charles 'Boss' Kettering's challenge to his engineers: to rid Cadillac V8s of their inherent roughness. The result was Cadillac's 90hp Type V-63 V8 built with crankshaft connecting-rod journals spaced at 90 degrees instead of the 180-degree intervals that were conventional for the time. Although every V8 maker quickly followed suit to achieve similar gains in smoothness, that hasn't discouraged a few OEMs - including GM - from reconsidering 180-degree " flat-plane " cranks. The recently announced 2023 Chevrolet Corvette Z06 is the newest wave in this technological tide (to hear the engine: https://youtu. be/8iQqi9s2Q2E). 10 September 2021 According to a highly-placed GM Propulsion source, the company's V8 past is back: an all-new DOHC V8 earmarked for the upcoming Corvette Z06 will be equipped with a flat-plane crank to assure that the intake and exhaust events in each cylinder bank are spread 180 degrees apart. Expectations are that GM will shorten the current 6.2-L Flat plane benefits What's inspiring some automakers to reconsider use of flat-plane-cranks are the compelling advantages exclusive to such designs. They're notably lighter and have less rotational inertia. Surrounding crankcases can be lighter and smaller. Racing-engine designers appreciate every cubic centimeter of volume saved, every gram of weight trimmed, and a flat-plane crank's inherent ability to spin more rapidly with GM Propulsion has been developing its new DOHC V8 with flat-plane crank in the Corvette C8R endurance racecar. AUTOMOTIVE ENGINEERING CLOCKWISE FROM TOP LEFT: GM; FORD; CHEVROLEThttps://www.youtube.com/watch?v=8iQqi9s2Q2E