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Rocker stands and shafts

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The pushrod valvetrain, while having great advantages for engine packaging, has the distinct disadvantage of not having a very direct connection between cam and valve, as is the case with overhead cam (OHC) engines. Even in the case where finger followers with roller bearings are used, the stiffness of the system is higher than is typically the case with an overhead valve (pushrod) system. As has been stated in previous RET-Monitor articles on pushrods, efforts are always being made to...

Triple springs for drag boats

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Who could imagine using the same set of valve springs for more than two years in a nitrous-infused 565 cu in V8 engine that competes in the quarter-mile on water? Wayne Gaskamp has been able to accomplish just that with his 1800-plus hp engine that propels Mike DeClark's F Bomb drag boat in two categories of National Jet Boat Association (NJBA) competition, the seven-second and unblown fuel jet classes. The NexTek-polished Manley triple springs of lightweight tool steel have been...

Stem stiffness and seating

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In developing a race engine it is common to evolve valve-lift profiles constantly to improve the 'breathing' of the engine. The aim is to increase volumetric efficiency or, more precisely, to increased the trapped mass of fresh, unburned charge. In the case of race engines this often leads to the use of more 'aggressive' cam profiles. By 'aggression' in the case of valve-lift profiles, this means higher accelerations and the derivative of acceleration with respect to...