LSA (lobe separation angle) numbers can be interpreted like this: the higher the # the less overlap, the lower the # the more overlap. Overlap is defined as the # of degrees that both the intake and exhaust valves are open. The longer both valves are open at the same time, the more diluted the incoming air/fuel charge is at an idle, thus at an idle it tends to make for a rough "poppity pop". But at high rpm's you need the overlap to help get the cylinder filled. When the exhaust is being pushed out of the cylinder by the piston, if you start to open the intake valve, you can use that velocity to help start to pull in the air/fuel charge. That is a basic description, a whole lot more is going on than just that tho.