How to calculate camshaft duration?
- Lobe Centers. Imagine a line passing from the center of the cam directly through the highest point on the cam lobe.
- Calculating Valve Lift. Net valve lift is a function of camshaft lobe lift and rocker arm ratio. ...
- Finding TDC. ...
- Degreeing the Cam. ...
- Intake Opening Method. ...
- Intake Centerline Method. ...
- Calculating Valve Overlap. ...
What does duration of camshaft mean?
Duration Camshaft durationis the amount of crankshaft rotation that occurs as the cam lobe moves the lifter off of the base circle; it is measured in crankshaft degrees to make it easier to degree (check) the cam to make sure it is positioned properly in the engine.
What does cam duration mean?
What does camshaft duration mean? DURATION: Duration is how long the cam holds the valves open. It’s expressed in degrees of crankshaft rotation (remember, the cam rotates at half the speed of the crank). A 280-degree-duration cam holds the valves open longer than a 260-degree-duration cam.
What is a camshaft and how does it work?
The camshaft is critical to the basic function of an engine. Comprised of two distinct parts, the cams and the shaft, the camshaft is the element that enables valves to open. As the shaft rotates, the egg-shaped cams (or "lobes") push the valves open in sync with the crankshaft gear. A collection of camshafts from the engines of cars and trucks.
What is a good 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 increasing cam duration do?
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.
How 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 makes a cam sound choppy?
Registered. 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.
Does a bigger cam mean more power?
Are Bigger Cams More Powerful? Yes. A bigger cam will open the intake valve wider, allowing more fuel and air into the cylinder.
How does a cam make more horsepower?
Performance cams increase the duration and timing of the valve openings during the engine stroke, increasing horsepower and making your car accelerate more quickly. You'll idle slightly rougher with a performance cam, but get a throaty rumble that's desirable for some gearheads, depending on your vehicle.
What makes a cam sound lumpy?
what makes the cam have that lumpy sound? The overlap of the exhaust valve closing and intake valve opening causes the engine to be inefficient at low speed which results in the lumpy idle. The closer the Lobe Seperation Angle the more the overlap, the more duration the more (typically) the overlap.
How do you get lumpy idle?
You can get a lumpy idle by retarding the timing and adding too much fuel.
How do you choose a camshaft?
0:402:53How To Choose The Right Cam - YouTubeYouTubeStart of suggested clipEnd of suggested clipBe easy on valve train parts have long durability. And be economical typically for this setup theMoreBe easy on valve train parts have long durability. And be economical typically for this setup the budget is the limit.
Why do cammed engines chop?
0:000:49Why Camshafts “CHOP” At Idle Explained - YouTubeYouTubeStart of suggested clipEnd of suggested clipThe more duration your camshaft. Has causes more overlap. And also a lower low separation angleMoreThe more duration your camshaft. Has causes more overlap. And also a lower low separation angle causes more overlap as well they are contributing factors.
What does an aggressive cam do?
What is an Aggressive Cam? Most people look at a large or a fat cam lobe and automatically assume it is aggressive. They might also say that it has an 'aggressive ramp'. The reality is that you cannot visually see if a cam is 'aggressive' or not.
Why do race cars idle so high?
The ones that have higher idle speeds do so because they have aggressive valve timing (hot cams) that do not have good combustion quality at low speeds, even with variable valve timing.
How does cam lift affect power?
CAMSHAFT LIFT Lift describes (usually in millimetres) how far the valves open – the higher the lift, the taller the camshaft lobes have to be to achieve this. More lift gives more flow, which, in turn, usually gives more power, and with only very minor ill-effects to performance elsewhere in the rev range.
What do high lift camshafts do?
1:135:35Camshaft - High Lift and Duration - Increase Horsepower - YouTubeYouTubeStart of suggested clipEnd of suggested clipSo one thing that you can do in order to push that valve down further. And allow more air to flow inMoreSo one thing that you can do in order to push that valve down further. And allow more air to flow in is have a higher lift. So if we had our camshaft here everything that you see in pink.
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.
What is the difference between lift and duration?
0:329:59What is the Difference Between Lift and Duration of a CamshaftYouTubeStart of suggested clipEnd of suggested clipIt's not going to last that long if you do so lift is certainly a very very important number theMoreIt's not going to last that long if you do so lift is certainly a very very important number the duration is how long once it starts to ramp up and the valve starts to open the length of time.
How to tell the duration of a camshaft?
When measuring the duration of a camshaft, it is measured in degrees of rotation.
What is the measurement of camshaft rotation?
When measuring the duration of a camshaft, it is measured in degrees of rotation. These degrees however, are not measured in camshaft rotation, but rather, the rotation of the crankshaft. When you look at the cam card, it will list several numbers that will dictate how this particular cam will operate in your engine.
What is a single pattern camshaft?
Single-pattern camshafts have the same duration and lift for the intake and exhaust valves, but if there are different lift and duration numbers for the intake and exhaust, these are called split-pattern or dual-pattern camshafts. When you increase the duration of a given camshaft, you shift the power and torque curves upward in the rpm range.
What is the best camshaft for a stock engine?
Camshafts that carry up to 220 degrees of duration at .050-inch lift are generally best for use with a stock, unmodified engine. Once you go beyond 220 degrees of duration, intake vacuum drops, and this causes issues with idle quality.
Why is the intake valve open at lower rpm?
Using a longer duration camshaft at lower engine rpm, causes the intake valve to be open too long for maximum efficiency, and allows some of the air and fuel mixture to get pushed out through the exhaust, and even back into the intake manifold (this is called reversion).
How to choose a camshaft?
Choosing a camshaft is easy. You can go to a cam manufacturer’s web site (Comp Cams in this case), and the brief description gives you the intended usage of each camshaft. If you are looking for a professional recommendation, calling the Comp Cams help line can you a professional’s opinion , or even a custom ground camshaft.
How many degrees of separation for a camshaft?
Most replacement camshafts with duration of less than 200 degrees at .050 inch typically have lobe separations of 112 to 114 degrees. Camshafts for mid-range performance typically have 110 to 112 degrees of lobe separation. With racing cams, you will find lobe separations that range from 106 to 108 degrees.
How to choose a camshaft?
If your knowledge is limited and you are set on selecting a cam yourself, pay the closest attention to two elements that are advertised by all camshaft manufacturers. First is the RPM band. This RPM or power band will denote the efficiency range that the camshaft was designed for and is typically displayed as "1500-6500RPM" for example. Match this RPM band closely with the intended use of the engine. Street cars will tend to spend more time at low RPM than High RPM, so an idle-5,500 or 1,500-6,500 would be best. Likewise, a high RPM race car that spends most of its time in the upper ranges will typically like cams that state 2,500-7,000 RPM or 3,500-8,000 RPM as two examples. The second element is the description or characteristics explanation of the camshaft. Most cam manufacturers put together a two or three sentence description of what the camshaft is best used for and/or it’s performance characteristics. These descriptions are like cliff notes for cam selection instead of having to read and understand the whole novel. Pick the one that describes best what you want and your intentions for the engine and you will typically make a wise choice. At JEGS we offer excellent Camshaft Manufactures such as Comp Cams, Crane Cams, Edelbrock,Ford Racing,Chevrolet Performance,Mopar Performance,Lunati,Crower, and Speed Pro. We also have our own JEGSline of Camshafts that we are proud of as well. If you would like to contact us for our advice feel free to call our tech line 24/7 @ 1-800-345-4545 option 2 on the menu. Do not hesitate to utilize our JEGS Ask A Techoption and submit your questions to one of our experienced team members who will be excited to help you with any of your High Performance needs.
What are the different types of camshafts?
Understanding Camshaft Fundamentals. Camshaft Types. There are two major types of camshafts: Flat Tappet and Roller Cams . Flat Tappet (lifters) are in most V8's and literally have what looks like a flat bottom where the cam lobe contacts the tappet (lifter). Lifters are not actually flat on the contact surface.
What is cam lobe lift?
It's important to be aware of a few ways camshaft lift is talked about. Cam lobe lift, also called Gross Lift, is the distance a cam moves a lifter/tappet. Because a rocker armmultiplies the movement of the tappet, valve lift is not the same as cam lobe lift.
How to tell cam lobe separation?
Cam lobe separation is the angle in degrees between maximum lift of a pair of cam lobes. To picture cam lobe separation a little better, look at the end of a traditional V8 camshaft. Draw a line through the center of the cam out through the point of maximum lift on each cam lobe on a pair of lobes. You'll usually find the measurement between 104 and 115 degrees. It's important to note that Lobe Separation describes how the intake valve reacts in relationship to the exhaust valve in the same cylinder. Where cam lift and duration describe the effect of each lobe on a valve. Cam Lobe Separation is an important performance characteristic because it times the intake and exhaust valves. If the Lobe Separation angle was 0 degrees, both intake and exhaust valves would be opened and closed at the same time. That obviously won't work, but it may help us understand what happens as the separation angle decreases or increases on a cam.
Why are roller cams fatter?
Roller cams have fatter lobes because of the way the cam lobe contacts the lifter. Roller lifters reduce friction, increase RPM potential and allow higher valve spring pressures to be used. Flat tappet camshaftscan only withstand so much valve spring pressure pushing the lifter against the cam lobe.
How does a cam lobe affect idle?
Since the angle is narrower, the 2nd valve in the pair is beginning to open before the first one is closed. How far the first valve is open when the 2nd valve begins to open depends on the Cam Lobe Separation. (The shape of the cam lobe also effects this.) A narrow angle will increase cylinder pressure, make an engine idle worse and reduce idle vacuum. Cylinder pressure increases because after the exhaust stroke, the piston is pulling air into the cylinder. If the intake valve opens earlier, more air can be sucked into the cylinder.
What happens when the intake valve opens earlier?
If the intake valve opens earlier, more air can be sucked into the cylinder. If the Lobe Separation is Wider:As a cam turns, one valve opens. As the cam continues to turn, that valve starts to close. With a wider angle, the 2nd valve in the pair is starting to open later.
What is a camshaft?
A camshaft is really a device used to convert rotating motion into linear (up and down) movement. This is accomplished by use of a cam follower or lifter that starts on the round portion of the eccentric, which is called the base circle.
What is the column before duration on a camshaft card?
These are the center lines of the intake and exhaust lobes expressed in crankshaft degrees. The intake center line occurs 108 degrees After TDC while the exhaust center line is positioned at 116 degrees Before TDC. The intake center line is often used as a primary point for degreeing the camshaft.
What is a Camshaft Timing Card or Cam Card?
One area of confusion is certainly a camshaft timing card. All aftermarket and production camshafts use a series of terms and specifications to identify their operating characteristics. These may seem obscure and even perhaps baffling, but in fact these cam specifications lay out a simple way of determining exactly how a particular camshaft will operate in the engine. That’s vitally important when it comes to choosing the right camshaft.
What does +4 advance mean on a camshaft?
What this means is that when this camshaft was machined, the specs called for advancing the intake lobe four degrees. This is often performed on street camshafts as a way to enhance low-speed performance.
What is the length of a Summit Racing cam?
You will see that this Summit Racing cam offers duration in two different tappet lift specs of 0.006-inch and also at 0.050-inch. In the early days of camshaft design, the manufacturer decided the beginning and ending positions in terms of tappet lift. Some companies use 0.004-inch and others use 0.006-inch.
How much lift does a cam lobe have?
Note that in this particular case, both the intake and exhaust lobes generate a lobe lift of exactly the same amount: 0.321-inch. You will often see where the lift will be different for the intake versus exhaust.
Why do crankshaft degrees matter?
Crankshaft degrees are used because that’s the easiest way to measure these points on the actual engine. Keep in mind that the camshaft turns at half engine speed because the cam drive gear is twice as large as the crankshaft gear. That means the crankshaft has to spin twice for the cam to turn one revolution.
What is the camshaft duration?
Camshaft durationis the amount of crankshaft rotation that occurs as the cam lobe moves the lifter off of the base circle; it is measured in crankshaft degrees to make it easier to degree (check) the cam to make sure it is positioned properly in the engine.
How to determine camshaft duration?
If you're not sure of the duration of your camshaft but have determined the intake and exhaust closing points, you discover the duration by adding the opening and closing point values to 180 degrees. For example: if the intake valveopen value is at 0.050-inch lift of 2 degrees and has an intake closing value of 40 degrees, we simply add both amounts to 180 (2 + 40 + 180 + 222) and we have 222 degrees of duration at 0.050-inch lift. This works just as well for the ex-haust side.
How does degreeing the cam affect the intake valve?
This can be altered by degreeing the cam after it's been installed in the engine. Moving the camshaft from its installed position affects all four opening and closing points; generally, the most important is intake closing. So by advancing the cam, the intake valve closes sooner. While this improves low-speed torque, it compromises top-end power.
How to choose a camshaft?
Choosing the best camshaft depends on vast criteria. If you use your car for daily transportation, you'll want to consider a camshaft with shorter duration and relative lift. Most of the cam companies offer copious assistance to match the best cam with the type of driving or racing you do. If you're looking for something wild, remember to match the rest of your engine and vehicle to your cam choice. Transmission type, vehicle weight, stall speed, compression, cylinder heads, and much more only begin the list. In this section, we've only touched on the fundamentals of camshafts. If you'd like to learn more, visit the some of the cam manufacturer's Web sites (listed in the source box). They hold a wealth of camshaft knowledge that is ever-evolving, and the tech sections of these Web sites are packed with information. Understanding the basics of camshafts may be difficult at first, but after reviewing the information, you'll find that you've learned quite a lot. The knowledge that you gain will surely help you choose the best cam for your particular engine.
What is camshaft understanding?
Basic Camshaft understanding discussing lift, duration, degrees, overlap, dialing in cam timing, and grinds for max power and fuel efficiency and torque
How many lobes does a camshaft have?
One of the camshaft's most fundamental tasks is to transform its rotating motion into linear motion or lift. This is accomplished on a typical Chevy V-8with 16 lobes (an intake and an exhaust)--all of them ground to an eccentric shape called a lobe to allow each lifter to raise and fall above a base circle.
What is a dual camshaft?
A dual-pattern camshaft generally offers more exhaust duration to improve the flow of an otherwise marginal cylinder-head exhaust port. Intake Centerline. The cam's centerline specification is used to determine the position of the lobes on both the cam and as installed in the engine.
What is the camshaft type on an overhead valve engine?
On most overhead valve engines there are two main types of camshafts, either a flat tappet camshaft or a roller camshaft. Whether it’s your first time building an engine or you’re just looking for a performance upgrade, understanding camshaft specifications and design is a must.
What is cam profile?
Cam Profile. The cam profile is the actual shape of the camshaft lobe. A flat tappet camshaft is slightly more pointed on the nose of the lobe, while a roller lift camshaft has a more rounded profile on the nose of the lobe.
What is the separation angle of the intake and exhaust lobes?
This is the angle in degrees between the centerlines of the intake and exhaust lobes. A 112-degree lobe separation angle means that the peak opening points of the intake and exhaust lobes are 112 degrees apart. This measurement is another way of expressing valve overlap, which is the amount of time that both valves are open on the same cylinder. If the lobe separation angle were 0 degrees, both the intake and exhaust valve would open and close at the same time. Measurements typically range between 104 and 115 degrees.
How to measure cam lobe lift?
Typically camshaft manufacturers list this measurement by multiplying the cam lobe lift by the stock rocker arm ratio, usually 1.5:1. For example, if your cam lobe lift is .319 and you're using a 1.5:1 rocker arm ratio, you can take .319 x 1.5, which is .479 inches of overall valve lift.
What is the round part of the cam lobe called?
The base circle is the round portion of the cam lobe where the valve lash adjustments are made. A slight high spot on the base circle is called base circle runout.
What is the heart of an engine?
Some might refer to the camshaft as the brain or heart of the engine. It determines when, how long, and how far the valves open and close in relation to the pistons. For every two revolutions of the crankshaft the camshaft rotates one revolution.
How to explain camshaft lift?
The easiest way to explain camshaft lift is to think of it as how far the valve opens to its furthest point off of the valve seat. Camshaft duration can be simply explained as how long the valve stays open off of the valve seat. These two very simple movements are ultimately what establish how much horsepower can be made with a camshaft, ...
Who explains how the camshaft plays into this concept with a simple analogy?
Yoder explains how the camshaft plays into this concept with a simple analogy.
What is the bottom end of an engine?
The bottom end of the engine is just a big air pump, so all it does is just move air around. The camshaft is the software controlling your valve moments, so if the valve timing and the amount the valves are open don’t match what the heads, valvetrain, or induction system like, the engine won’t make as much power as it should.
Do you need to guess camshaft numbers?
With today’s modern engine building technology, you don’t need to guess on numbers or just select a camshaft based on how well it works for someone else. Knowing your flow numbers is important to getting the right camshaft lift. If you make any changes to the cylinder via porting, that needs to be considered when selecting a camshaft.
Does a camshaft make more torque?
“Duration wise it’s more relevant to RPM range. The less duration the camshaft has, the more torque an engine will make; the higher the duration, the engine will make more top-end horsepower, but not as much torque . One of the reasons they don’t make as much ...
