Results
Intake opens
6.0 deg
Intake closes
42.0 deg
Exhaust opens
54.0 deg
Exhaust closes
2.0 deg
Valve overlap
8.0 deg
Formula / model
ICL = LSA - advance, ECL = LSA + advance, event timing = centerline +/- duration / 2
This camshaft timing and valve event calculator helps you see how duration, lobe separation, and advance shift the timing events that shape engine behavior.
Enter your current numbers or target values below, then use the live results to review intake opens, intake closes, exhaust opens, exhaust closes, and valve overlap before you commit to the next parts or setup change.
Camshaft valve events dictate exactly when the engine breathes in and out relative to the crankshaft position. Intake Valve Opening (IVO) and Exhaust Valve Closing (EVC) determine the overlap period, which fundamentally alters vacuum, idle quality, and where the engine makes peak torque.
The advertised or @0.050" duration determines how long the valve remains off its seat. Shorter duration builds high dynamic compression at low rpm, resulting in snappy throttle response and high vacuum. Longer duration bleeds off low-speed cylinder pressure but allows the engine to breathe massively at high rpm.
Comparing tight vs. wide lobe separation characteristics.
| Characteristic | Tight LSA (e.g., 106°-110°) | Wide LSA (e.g., 114°-118°) |
|---|---|---|
| Idle Quality | Choppy / Rough | Smooth / Stable |
| Engine Vacuum | Lower (Poor for power brakes) | Higher (Better for accessories) |
| Power Band | Peaky, strong mid-range | Broad, flatter torque curve |
| Application | Drag Racing, Carbureted | EFI, Turbo/Blower, Street |
Installing a camshaft "advanced" (for example, +4 degrees) closes the intake valve sooner. This traps cylinder pressure earlier in the compression stroke, improving low-end torque and throttle response, at the slight expense of top-end power.
Overlap occurs when both the intake and exhaust valves are open simultaneously near TDC. High overlap draws in fresh fuel tightly behind exiting exhaust gases (scavenging), but causes a massive loss of idle efficiency.
These are the next calculator pages most likely to be useful once you have this result in hand.
Valve Train
01Original and changed valve lift from lobe lift, rocker ratio, and lash.
Engine Geometry
02Static compression ratio from swept and clearance volume inputs.
Performance
03Quick torque and horsepower estimate from displacement, rpm, VE, and boost pressure.
How cam duration and lift directly determine where VE peaks in the RPM range.
Why cam timing interacts with displacement to shape the torque curve.
How bore-to-stroke ratio affects the RPM range the cam should be optimized for.
It estimates intake opens, intake closes, exhaust opens, exhaust closes, and valve overlap from values such as intake duration, exhaust duration, and lobe separation angle.
Start with intake duration, exhaust duration, and lobe separation angle because those are the core values that move intake opens the most. Then refine the secondary inputs to match the exact combination.
It is a solid planning tool built around the stated formula and assumptions, but final results still depend on real measurements, hardware tolerances, tuning, and operating conditions.
Yes. Change the inputs to reflect your exact parts, operating target, or comparison scenario, then review how the outputs respond before you make the next decision.
A useful next step is to compare the result with Valve Lash & Rocker Arm Ratio Calculator, Compression Ratio Calculator, and Horsepower and Torque Estimator so the rest of the combination stays aligned.
