Some of the recent articles concerning pushrod valvetrains have tried to explain the importance of valvetrain stiffness. The advent of the Spintron tester, and its widespread deployment in the r&d shops of engine builders, has given engineers a better insight into valvetrain behaviour, especially the deviation from the 'theoretical' valve lift curve we might expect the lifter/pushrod/rocker to impart to the valve. Anything that doesn't behave as an infinitely stiff member...
In many areas of motorsport, components are pushed to their limit to squeeze out as much performance as possible. Finding that balance between more performance and too high a risk of failure is something that engine builders are constantly wrestling with. Ron Shaver of Shaver Engine Specialties, in Torrance, California, builds Tony Stewart's World of Outlaws 410 cu in sprint engines. And, like many other parts of his engines, valve springs are a vital area where risk and reward have to...
The poppet valve is almost universally used in all forms of transport powered by an internal combustion engine. Motorsport has always had a buoyant two-stroke sector in the motorcycle arena, although this is on the wane now with Grand Prix motorcycle racing having bidden farewell to its last two-stroke class at the end of 2011. So, we have confined ourselves to a four-stroke future, and this generally means poppet valves. Brave attempts by forward-thinking engineers over the generations to...