What real difference does the lsa on a cam make?

All things being the same in a cam grind, except the Lobe Separation Angle itself.......... a 108-LSA will close the intake valve sooner then a 110 -LSA

.....for example.

If you wanted to run a cam with a given duration that compliments your compression and or the type of fuel you wanted to use ---but the rpm band was a little low for your liking ---and you wanted a little more higher rpm engine.
....instead of running a cam with 230@50 duration ground on a 110 LSA...
you could run a 234@50 on a 108 and the intake valve would close at the same time giving you the same cylinder pressure as the smaller cam.

Your rpm band would be higher and more narrow BUT.....in the end.. will make more torque and power.

If you look at most racing cams they are on the tight side.

Engines with high compression,great flowing heads and bigger cubic inches change the formula and more power with a wider LSA.

Cams with a tighter lsa are a little harder to tune and can run very radical.

If your running none ported stock heads and stock compression you want a tighter LSA.

Here is a way to get your engine in the ball park..

Example...318 cubic inches divided by 8 cylinders is 39.75
Take that number....39.75 and divide it by the size of the intake valve
39.75 divided by 1.78(stock 318 valve size) = 22.33

Find the number on the chart and this is the best LSA for a lower compression stock headed engine.