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...
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...
Rockers are a critical element in the valvetrain of any overhead-cam engine, and so we should not be surprised to find that their development continues to be the subject of much activity in racing circles. Much of the racing in the US, for example - including the incredibly popular NASCAR categories and their various 'feeder' series - is based on engines using the overhead-cam (pushrod) valvetrain. In recent years, NASCAR has allowed the various competitors in its Sprint Cup race...
Containing a valvetrain that works with a four-cylinder, heavily boosted engine that develops more than 1000 hp should be a difficult enterprise, but Time Attack factory Scion (Toyota) team WORLD Racing is having no problems with its steel coil valve springs. Time Attack, which is a form of American road racing where the car-driver tandem compete for a time slip is "a bit of road racing with a bit of a drag racing element to it," according to Rob Cardona, WORLD Racing's...
In the recent Race Engine Technology article on valves, there was some discussion of the merits of hollow valves, and indeed the subject has been covered by Anne Proffit and I in these Monitor articles in the past. We should briefly restate here the reasons for hollow valves. The first and more obvious reason is mass reduction in cases where a reduction in stem axial stiffness does not compromise the proper action of the valve or present problems through lack of bending stiffness. The...