Camshaft Duration & Overlap Calculator
Calculate valve overlap, lobe separation angle (LSA), centerlines, and total duration from your cam card's valve timing events.
Before Top Dead Center
After Bottom Dead Center
Before Bottom Dead Center
Negative if closes BTDC.
Summary: For a camshaft with intake events at 5° BTDC to 43° ABDC and exhaust events at 53° BBDC to -3° ATDC, the calculated intake duration is 228° and exhaust duration is 230°. The resulting physical lobe separation angle (LSA) is 113.5° with a total valve overlap of 2.0°. This overlap mathematically indicates a relatively smooth idle characteristic at 0.050" lift.
Advertised vs @ 0.050”
Always use @ 0.050" figures when computing overlap and centerlines for modern engine building. Advertised durations (e.g. 280° vs 230° @ .050") will result in massive theoretical overlap numbers that don't reflect true cylinder filling characteristics.
Methodology
Duration: Opens + Closes + 180°
Centerline: (Duration ÷ 2) - Opens
LSA: (Intake Centerline + Exhaust Centerline) ÷ 2
Overlap: Intake Opens + Exhaust Closes
Frequently Asked Questions
What does Valve Overlap do?
Overlap is the period where both the intake and exhaust valves are open simultaneously. High overlap uses exhaust scavenging to pull fresh intake charge in at high RPM, making big top-end power. At low RPM, it causes exhaust reversion, creating a choppy idle and poor torque.
What is Lobe Separation Angle (LSA)?
LSA is the physical angle in camshaft degrees between the centerline of the intake lobe and the centerline of the exhaust lobe. It CANNOT be changed without grinding a new camshaft (unlike centerlines, which can be adjusted with adjustable cam gears).
Should I advance or retard my cam timing?
Advancing the cam (Intake Centerline < LSA) closes the intake valve earlier, building more cylinder pressure and shifting the power band to lower RPM. Retarding the cam shifts the power band upward for more top-end.
Disclaimer & Legal Notice
All tools and calculators provided by Lapsite are for informational and educational purposes only. While we strive for mathematical precision, these results are approximations and should not be used as the sole basis for critical engineering, financial, or safety decisions. Lapsite Ltd and its creators provide no warranty, express or implied, regarding the accuracy or fitness of these calculations for any specific use.Always double-check calculations independently, especially for safety-critical components such as brakes, suspension, or structural changes. By using these tools, you agree that Lapsite Ltd is not liable for any mechanical failure, financial loss, or injury resulting from the use of this data.
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