Why is it important to measure the valve spring free length during a cylinder head overhaul?

1. Over time, valve springs lose tension and fatigue, causing their free length to shrink; if below specification, it will cause valve float at high engine speeds.
2. It determines the height of the camshaft lobes required for the engine.
3. A shorter spring free length increases the speed at which the valves open.
4. It is used to calculate the correct thickness of the head gasket.