what rpm can it take?

[Capri306]

Jeff, you're right; valve spring pressure is vital to the stability of the engine as speed climbs. However, you probably also realize that most people don't want to change valve springs (one of the most overlooked parts, imo). Also, that higher valve spring pressure creates more drag on the engine, which is why I like the solid rollers so much. Consequently, if you're spinning in the 7k+ range, that drag becomes inherent to the territory you're in, right?

I suppose while we're on it, this is kind of like the whole question regarding the "maximum lift" you can have on (insert cylinder head manufacturer name here) heads. It's not about the lift, it's about the timing of the events that's important. So, you're absolutely right on about the duration, which is typically closely linked to the ramp rates of high-rev cams.