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Originally Posted by longassname
The measurements I posted thus far in this thread are really only for the benefit of those who already understand what they mean. They are important for the design of the components not to direct peformance improvements. Well....that's true with the exception of the valve springs. Subaru engineers pride themselves in maintining exceptionaly light spring tensions so the factory springs really aren't good for a performance set up. To get more horse power we do either or both of two things: 1) get more air into the engine per revolution 2) run higher rpms. Doing either of those things can quickly overwhelm the light valve spring tensions--particularly the seat tension. This is called valve float. It's also called a big loss of power. The supercharged cars are showing evidence of either inadequate exhaust cam duration to clear the cyllinder or valve float or both above 3500 rpms. As it turns out, having measured things up, supercharged or not the most sensible way to do the cams is to do the cams, valves, and valve springs together.
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There have been figures and figures posted, but I have seen nothing in respect of the average torque, shock torque or power, involved in driving the camshafts. Given the length and convoluted nature of the SVX cam belt, and the fact that each is driving valve gear for six cylinders and not four as is the nearest comparable, this aspect should be taken into account.
The increased lift and spring tensions being considered are a major factor involved in this issue. I would suspect there could be surprises in store. Was this a limiting factor in the minds of those who engineered the original?
