What Is Camshaft Duration

Measuring duration at 0.050-inch tappet lift has become standard with most high-performance cams. Most engine builders feel that 0.050 duration is closely related to the rpm range where the engine makes its best power.

What does camshaft duration mean?

Duration is how long the valve is off its seat. It is listed in degrees of crankshaft rotation. When someone refers to a “big cam,” they mean it has longer duration, not higher Lift.

What does increasing cam duration do?

Increasing duration keeps the valve open longer, and can increase high-rpm power. Doing so increases the RPM range that the engine produces power. Increasing duration without a change in lobe separation angle will result in increased valve overlap.

How does cam duration affect torque?

Duration has a marked affect on the cams power band and drivability. Higher durations increase the top-end at the expense of the low end. As a general rule, cams with 220-235 degrees of duration tend to produce good low end torque.

How do I know what camshaft to buy?

The rpm range is the range where the engine performs best. When selecting a camshaft, choose one with an rpm range that matches the other components of your vehicle and its intended use. Follow this link for more about Basic Operating RPM Range.

What does a mild cam mean?

A mild cam is usually a little bigger than the stock cam. Most of the “Mild” cams have just a bit of lope to them and will give you a bit more power than the stocker. My car, unfortunately, has a mild cam in it with it’s TR224. Still makes more power than stock but idles and rides real close to stock.

Does a bigger cam give more power?

Does a camshaft increase horsepower? Yes, a camshaft adds 10 to 20 horsepower depending on the setup. To get the full potential of the high-performance camshaft, you’ll have to swap out additional components like the air intake, exhaust manifold, injectors, and valve heads.

Why do you degree a camshaft?

Pit Stop with Marlan Davis: Degreeing a custom cam ensures its maximum performance, helps prevent piston-to-valve contact, and protects against assembly error. The bigger the cam, the more important this is.

What Is a Stage 2 cam?

Tuner Series Stage 2 Camshafts are designed to optimize horsepower and torque on engines featuring free-flowing intake and exhaust tracts, increased compression, and upgraded valvetrain.

What makes a cam choppy?

LSA (lobe separation angle) determines the choppiness, it has to do with the overlap of when both valves are open, as in when the exhaust valve is closing and the intake valve is opening to pull fresh fuel in on the intake stroke after pushing out the burnt fuel. Most GM cams come on a 112, 114 or 116 LSA.

What is considered a lot of cam overlap?

To maintain sufficient idle and vacuum qualities, the cam tech recommends the cam be ground on, say, 112-degree LCA, which gives an overlap of 66 degrees. For a typical performance-headed 350, the optimal LCA is usually 108 degrees.

Does cam duration affect idle?

Again, keeping all else constant, more duration will make the engine less efficient at low rpm, with more overlap dilution of the induction charge, and the later intake valve closing reducing the trapping efficiency. Therefore, a long-duration cam will cause rough running at idle (lope) and a loss of low-rpm torque.

Do camshafts increase rpm?

Generally, cams with smaller duration numbers make peak horsepower at lower rpm. These cams are often used for stock replacement, daily driver, and towing applications. As you increase the duration, you increase the peak power the engine can make. However, you also move the power curve higher in the rpm range.

What is and when does overlap happen with cam timing?

Overlap is when the intake and exhaust valves are open at the same time. It is expressed in degrees of crankshaft rotation. Not all camshafts have overlap. If they do, it happens at the end of the exhaust stroke and the beginning of the intake stroke.

How do you size a cam?

Take your digital caliper and measure the smallest diameter on the cam. This is called the base circle. This cam measured at 1.10 inches and 87 thousandths. The next value you will need is the largest diameter on the cam, the lobe part, which is called the base circle and lobe lift.

What is duration and lift on a camshaft?

Lift and duration are the primary factors that determine a cam’s profile. Lift is the amount a cam lobe actually moves a valve off its seat and is measured in fractions of an inch. Duration is the amount of time a cam keeps a valve off of its seat, measured in degrees of crank rotation.

What is a good mild cam for 350?

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