I've been asked "I have the valve opening & closing points of a cam, but how do I calculate the intake and exhaust centerlines, and the LSA or lobe center angle?"
For a cam with 245 degrees intake, 264 degrees exhaust, 39 degrees overlap:
For the intake lobe: (intake closing - intake opening) / 2, then add 90 degrees
Example for 10-55 timing: 55 - 10 = 45, divide by 2 = 22.5, add 90 = 112.5 degrees ATDC
For the exhaust lobe: (exhaust opening - exhaust closing) / 2, then add 90 degrees
Example for 72-32 timing: 72 - 32 = 40, divide by 2 = 20, add 90 = 110 degrees BTDC
LSA: (intake CL + exhaust CL) / 2
112.5 + 110 = 222.5 / 2 = 111.25 degrees
I just wrote an Excel spreadsheet that calculates this automatically from your input, e-mail me for a free copy: jdiamond (at) optonline.net
