Stop in for a cup of coffee
I never quite understood LC and IC and why both measurements are needed.
Intake center line is where you usually degree the cam to and is where the intake lobe center is.... You can also calculate it using the intake open and intake close numbers...
Lobe separation is where the exhaust center line is from the intake lobe center line... If they don't give it, you can calculate it from intake lobe center line and lobe separation angle... Or calculate the exhaust lobe center line using the exhaust open and exhaust close numbers....
Very few manufacturers give overlap numbers, Chrysler is one of the few that does... However I like to look at overlap as it gives an idea of how much duration both valves are open which affects idle vacuum... The larger the overlap, the lower the cylinder pressure and lower the intake vacuum...
Intake closing also is a major factor in dynamic compression... The later the intake valve closes, the less dynamic pressure... The earlier it closes, the higher the dynamic compression.... The cylinder can't develop compression until both valves are closed when the piston is travelling upwards.... The intake valve is the last one to close...
Overlap also affects cylinder scavenging, how well the cylinder can get all of the old burnt gasses out of the cylinder to make room for the new intake charge... You can't burn the old gasses again, so cylinder scavenging is important for making power and efficiency... You want to get all of the old burnt gasses out of the cylinder to make room for the "fresh" charge to come in... Any left over burnt gasses in the cylinder is taking up room preventing you from getting new fresh air and gas in to burn for the next cycle....
Plus when the intake valve closes, it creates a pulse in the intake... This pulse can affect how the cylinder fills... If you tune the pulse correctly and it gets to the intake valve just as it opens creates a 'ram effect' which helps push the charge into the cylinder... That was the theory of the ram induction and max wedge intakes... The long ram induction manifolds were typically tuned to 2500 RPM and the short ram were typically tuned to 3500 RPM, where the max wedge intakes were typically tuned to 6500 RPM...
The pulse is determined by the mach number of the flow in the intake which is determined by the area and length of the port... If you tune the intake using that theory you can make it efficient for the RPM range that you need....