TDC BDC BDC0.050″
TDC BDC BDC0.050″
TDC BDC BDC0.050″
TDC BDC BDC0.050″
Intake Duration at 0.050″
crank degrees
Exhaust Duration at 0.050″
crank degrees
Advertised Intake Duration
crank degrees
Advertised Exhaust Duration
crank degrees
Lobe Separation Angle
cam degrees
Advance
cam degrees
Valve Lift Intake
1/1000 inches
Valve Lift Exhaust
1/1000 inches
Intake Duration at 0.050″
crank degrees
Exhaust Duration at 0.050″
crank degrees
Advertised Intake Duration
crank degrees
Advertised Exhaust Duration
crank degrees
Lobe Separation Angle
cam degrees
Advance
cam degrees
Valve Lift Intake
1/1000 inches
Valve Lift Exhaust
1/1000 inches
Intake Duration at 0.050″
crank degrees
Exhaust Duration at 0.050″
crank degrees
Advertised Intake Duration
crank degrees
Advertised Exhaust Duration
crank degrees
Lobe Separation Angle
cam degrees
Advance
cam degrees
Valve Lift Intake
1/1000 inches
Valve Lift Exhaust
1/1000 inches
Intake Duration at 0.050″
crank degrees
Exhaust Duration at 0.050″
crank degrees
Advertised Intake Duration
crank degrees
Advertised Exhaust Duration
crank degrees
Lobe Separation Angle
cam degrees
Advance
cam degrees
Valve Lift Intake
1/1000 inches
Valve Lift Exhaust
1/1000 inches
Glossaryexpand
TDC
Top Dead Center
Piston at highest point
BTDC
Before Top Dead Center
Piston rising
ATDC
After Top Dead Center
Piston falling
BDC
Bottom Dead Center
Piston at lowest point
BBDC
Before Bottom Dead Center
Piston falling
ABDC
After Bottom Dead Center
Piston rising
CombustionBBDC
ExhaustABDCBTDC
IntakeATDCBBDC
CompressionABDC

An interactive camshaft calculator where engine builders can see how valve overlap (and boost efficiency) is affected by a camshaft’s physical design.

How to use MGI’s Camshaft Calculator

When shopping for camshafts from different manufacturers, enter each of their supplied cam card specs into MGI’s Camshaft Calculator. You can compare up to four cam cards. For boosted applications, compare especially the valve overlap between each of your available cam card selections — The more valve overlap, the less effective your blower/supercharger will be.

That being said, certainly consider what each camshaft manufacturer suggests as their overall best guideline for your specific application. For more information and helpful links, scroll to the content below.

What is valve overlap and why is it important

Valve overlap is mostly a function of duration and lobe separation angle (LSA), and to some minor degree valve lift. If the LSA remains the same but you increase the duration, the amount of overlap will also increase. Overlap is the span (measured in crankshaft degrees) when the exhaust valve and intake valve are both open.

For normally-aspirated engines, overlap generally improves engine performance by starting the intake cycle before the exhaust cycle has finished. As overlap increases, this tends to make the engine idle quality more erratic or lumpy, while improving mid-range and top-end power.

camshaft overlap area

But what about blown or supercharged engines?

In a blown engine, the larger the overlap area, the more the boosted charge is being blown straight out the exhaust tailpipe without being compressed in the cylinder. That’s wasted power right there. The larger overlap becomes associated with lower overall engine/blower efficiency and power loss.

Don’t like power loss? We don’t either. That’s why we’ve designed an interactive camshaft calculator to help you better evaluate your options.

MGI SpeedWare’s camshaft calculator is a free tool made by — and for — car enthusiasts. This tool is a work-in-progress and is not intended to substitute professional advice.
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