Camshaft Duration Calculator

A camshaft's timing specs determine how an engine breathes — and the Camshaft Duration Calculator translates those specs into the exact valve events happening inside your engine. Enter your intake and exhaust duration at 0.050", advertised durations, lobe separation angle, cam advance, and intake/exhaust valve lift to see your valve overlap, plus precise intake opening and closing, exhaust opening and closing, and intake centerline positions in crankshaft degrees.

degrees

Intake lobe duration measured at 0.050" lift

degrees

Exhaust lobe duration measured at 0.050" lift

degrees

Advertised intake lobe duration

degrees

Advertised exhaust lobe duration

degrees

Angle between intake and exhaust lobe centers

degrees

Cam timing advance/retard from straight up

inches

Maximum intake valve lift

inches

Maximum exhaust valve lift

Results

Valve Overlap

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Intake Opening

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Intake Closing

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Exhaust Opening

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Exhaust Closing

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Intake Centerline

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Frequently Asked Questions

What is valve overlap and why is it important?

Valve overlap is the period when both intake and exhaust valves are open simultaneously near top dead center. It helps scavenge exhaust gases and can improve cylinder filling, but too much overlap can cause rough idle and poor vacuum.

How does lobe separation angle (LSA) affect engine performance?

LSA determines the relationship between intake and exhaust events. Tighter LSA (108-110°) increases overlap and torque but reduces idle quality. Wider LSA (114-116°) improves idle and vacuum but may reduce peak torque.

What's the difference between advertised duration and duration at 0.050"?

Advertised duration measures from seat-to-seat at very low lift (typically 0.004-0.020"). Duration at 0.050" is measured at 0.050" lift and is more consistent between manufacturers for comparing camshafts.

How does cam advance affect valve timing?

Advancing the cam (installing it ahead of straight up timing) opens and closes all valve events earlier. This typically improves low-end torque but may hurt high RPM power. Retarding has the opposite effect.

What about blown or supercharged engines?

Forced induction engines often benefit from less valve overlap to prevent boost pressure from escaping through the exhaust. Wider LSA and different timing strategies help optimize scavenging without losing boost pressure.

How do I choose the right camshaft duration?

Longer duration moves the power band higher in RPM but reduces low-end torque and idle quality. Choose duration based on your intended RPM range, vehicle weight, transmission type, and desired characteristics.

What valve lift should I target?

Higher lift generally improves airflow but requires stronger valve springs and may limit RPM. Most street engines work well with 0.450-0.550" lift, while race engines may use 0.600-0.700" or more with appropriate valve train components.