you arent looking at the total duration though, the valve events are different
b303 224/224 at .50 lift 480/480 lift 112*
x303 224/224 at .50 lift 542/542 lift 112*
Not quite, they are the same.
Assuming you are talking about the lobe seperation angle, take this in...
5 + 5 = 10
7 + 3 = 10
The average of both is 5. Pretend that 5 is the LSA.
The LSA works the same way for both camshafts, because they have the same opening and closing events.
Intake Opening: 5* BTDC
Intake Closing: 39* ABDC
Exhaust Opening: 49* BBDC
Exhaust Closing: 5* BTDC
Take the intake side for simplicity, 5 + 39 = 44 degrees.
Add 180 degrees to represent the intake stroke (1/4 of a complete 4-stroke cycle) and you get:
180 + 44 = 224* (duration on the intake side).
Divide by two and you get the LSA - 112*. This works the same for both camshafts.