Camshaft timing relationships
Lobe Separation Angle (LSA) is the angle in camshaft degrees between the peak lift points of the intake and exhaust lobes: LSA = (Intake Centerline + Exhaust Centerline) / 2.
Cam advance or retard is calculated as (Exhaust Centerline - Intake Centerline) / 2. Advancing the cam shifts peak torque lower in the engine RPM band.
Valve overlap is the duration during which both intake and exhaust valves remain open simultaneously at top dead center: Overlap = (Intake Duration + Exhaust Duration) / 2 - 2 × LSA.
Worked example: Performance street camshaft
An engine camshaft with 106° Intake Centerline (ATDC) and 114° Exhaust Centerline (BTDC) has an LSA of (106 + 114) / 2 = 110.0° and 4.0° of ground-in advance.
With 270° intake and 276° exhaust advertised duration, valve overlap is (270 + 276) / 2 - 220 = 53.0°, delivering strong mid-range power with a noticeable street burble.
Camshaft timing inputs
Intake Centerline
Crankshaft degrees after top dead center (ATDC) where maximum intake lift occurs.
Exhaust Centerline
Crankshaft degrees before top dead center (BTDC) where maximum exhaust lift occurs.
CALCULATOR QUESTIONS
Camshaft LSA & overlap calculator questions
How does LSA affect engine performance?
A tighter LSA (e.g. 106°-108°) increases valve overlap, producing a choppier idle, higher cylinder scavenging, and stronger peak power, while wider LSA (112°-116°) widens the torque curve and improves idle vacuum.
What is valve overlap?
Valve overlap is the period around Top Dead Center between the exhaust stroke and intake stroke when both valves are partially open.