Camshaft Duration is the measurement of the time one valve begins to open until it finishes closing. Duration is measured in degrees of crankshaft rotation, not camshaft rotation. You’ll see duration specifications at . 050 inches.

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 cam 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.

How do you calculate cam duration?

1. Using a Dial Indicator and Degree Wheel, find the opening and closing points of the valves at 0.050 in. of lift. If the intake valve opens AFTER TDC, use a negative value. If the exhaust valve closes BEFORE TDC, use a negative value.
2. Add the numbers together.
3. Add 180° to find duration.

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.

What does a mild cam mean?

An RV or towing camshaft, which is considered a mild performance or an economy cam, will often have a narrower LSA, between 112 and 114 degrees. … These camshafts have a larger amount of overlap, which results in great mid-range torque and high-rpm power production, but poor idle quality and low idle vacuum.

Which is better more lift or more duration?

Designing a cam profile with more lift results in increased duration in the high-lift regions where cylinder heads flow the most air. Short duration cams with relatively high valve lift can provide excellent responsiveness, great torque, and good power. But high lift cams are less dependable.

Does a cam increase compression?

Overlap is the time in which both valves are open as the piston pushes exhaust out and starts to suck new fuel and air into the cylinder. … It’s not “just” the cam making the power, it’s the cam’s scavenging effect working as the RPM increases which increases cylinder pressure (dynamic or effective compression).

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 does cam overlap do?

OVERLAP. Overlap is the angle in crankshaft degrees that both the intake and exhaust valves are open. This occurs at the end of the exhaust stroke and the beginning of the intake stroke. Increasing lift duration and/or decreasing lobe separation increases overlap.

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What happens when you advance cam timing?

Advancing or retarding a camshaft’s timing from its original “zero” position causes the valve events to happen either earlier or later in the engine’s cycle. A camshaft that is advanced four degrees will cause each opening and closing event to occur four degrees of rotation sooner than before.

What do the numbers on the end of a camshaft mean?

The first two numbers are the degrees of opening being 210 for the intake and 218 degrees for the exhaust given normally at . 050 inch of lift. The next two numbers are the valve lift of intake and exhaust in thousands of an inch. The final number is the degrees of overlap.

What is a good mild cam for 350?

• Comp Cams 12-602-4 Hydraulic Flat Cam.
• Comp Cams Xtreme Energy 242/248 Hydraulic Roller Cam.
• SB Chevy Hi-Perf RV Cam And Lifter Kit.
• Lunati Bare Bones Hydraulic Flat Cam.
• Lunati Voodoo Hydraulic Flat Cam.
• Melling Hydraulic Flat Camshaft.

How much horsepower does a cam add?

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.

What gives a cam a rough idle?

The rough idle for long duration cams is due to two primary factors: Large valve overlap (the period at TDC exhaust where both intake and exhaust valves are open) causes an increase in exhaust residual fraction.

Why do big cams sound 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 causes a lopey idle?

A rough idling engine can be caused by spark plugs or spark plug wires. Spark plugs use the electrical current received from ignition coils to ignite the air/fuel mixture within the combustion chamber. A plug that is damaged or installed incorrectly can result in fuel being burned at an inconsistent rate.

Do cams cause misfires?

A worn camshaft can lead to an engine misfire, which in turn, causes an increase in tailpipe emissions.

What does retarding cam timing do?

Advancing or retarding the cam pushes the centerline of the camshaft to one side or the other of the crankshaft centerline. This changes the Timing of the valve opening and closing events, in relation to the position of the piston in the cylinder.

What is meant by Valve Timing?

Definition of ‘valve timing’ Valve timing is the exact timing of the opening and closing of the valves in a piston engine. … The intake valves rely on valve timing to open their ports at the correct time for the air and fuel ingredients.

What does lobe separation mean?

The lobe separation angle or LSA is the angle in camshaft degrees between the maximum lift points, or centerlines, of the intake and exhaust lobes. … It affects the amount of valve overlap; that is the brief period of time when both the intake and exhaust valves are open.

What is the difference between a Stage 1 and Stage 2 camshaft?

Stage 1: these are generally considered exhaust and intake modifications to an otherwise stock engine along with the appropriate EFI Tuner. … Stage 2: this is typically referred to an engine with a performance cam upgrade as well as the other components within a Stage 1 combination.

What are the three types of cam?

• Wedge or flat cam.
• Disk or Plate cam.
• Spiral cam.
• Cylindrical cam.
• Heart-shaped cam.
• Translating cam.
• Snail drop cam.
• Conjugate cam.

What is considered a stage 3 cam?

The Stage 3 cam is designed to work with some larger valves, port work, and upgraded carburetor or EFI system. This cam starts moving the power band a little higher in the RPM range (2500-6000). This is the biggest cam we recommend for a street application.

Do camshafts make car louder?

Yes, especially if it has a nice lope to it. All my cammed cars got louder after adding a cam. Yes, it will be louder. The cool factor goes way up to when you hear the choppy idle to!

What is a three quarter cam?

The original 3/4 race cams are the forerunners of today’s street-performance grinds. The term likely originated in the ’50s as the burgeoning hot-rod industry was modifying Ford Flatheads to drag race on airport runways and attempt top-speed runs on dry lake beds.

How do you check a cam lift?

Simply measuring the diameter of the base circle, and subtracting that from the largest diameter of the cam, the lobe lift, will calculate the lift of the cam.

What is considered a high duration camshaft?

A 280-degree-duration cam holds the valves open longer than a 260-degree-duration cam. Holding the valves open longer allows more air and fuel into the engine and also allows more to get out through the exhaust. Longer duration (higher number) improves top-end power but almost always sacrifices low-end torque.

Does cam timing affect ignition timing?

How does cam timing affect ignition timing? In a short, two word answer… it doesn’t. I get questions from people asking: “My cam is advanced 4 degrees, where should I set the ignition timing on my engine?” The complete answer is; Wherever your ignition timing is normally set at. Cam timing is VALVE timing.

How does a cam affect vacuum?

That means more duration for both the intake and exhaust lobes, because at high rpms it can be difficult to get air and fuel into the combustion chambers and exhaust gasses back out in time. … Together, those qualities in a camshaft harm the amount of vacuum any engine will pull in the intake manifold plenum.

Is Cam overlap good?

Any camshaft with a significant amount of overlap is not recommended for street-driven cars. The engine will have poor low-end power. For vehicles with power brakes, Low Vacuum also makes for a very hard brake pedal. Overlap also contributes to Exhaust Reversion, which isn’t good.