[blykins]

The intake .050" duration (along with the displacement and cylinder head flow) does control where the engine will peak the horsepower.

However, the LSA is just a number that plays into how much overlap the camshaft has. It doesn't change where the peaks occur or how broad the curves are, the overlap does that.

Exhaust duration should be based on how well the cylinder heads flow on the exhaust side, or if the application is a high/low rpm application, or if the application is forced induction, etc.