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.
To check your LSA you calculate it by adding the intake and exhaust Lobe Centerline figures together and dividing their sum by two (Ex: 112 intake Centerline + 116 exhaust Centerline = 228 / 2 = 114-degree LOBE SEPARATION ANGLE). There's more.
Definition & Description. 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.
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.
Valve lift is increased by using taller lobes on the camshaft and/or higher ratio rocker arms. Increasing valve lift improves airflow up to a point, so you want more lift in a performance cam. But airflow eventually peaks out because of restrictions in the cylinder head, intake or exhaust system.
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.
A flattened cam lobe will often manifest first at low rpm, especially for engines with hydraulic lifters. At idle and low rpm, the valve is barely open even when the cam is brand new; when the lobe flattens out, the valve may not open at all until the lifter pumps up at higher rpm.
A long-duration cam will only take the engine so far in terms of additional top end power and rpm whenever the engine is rpm-limited by the flow capacity and velocity of flow in the cylinder head ports. Therefore, a long-duration cam will cause rough running at idle (lope) and a loss of low-rpm torque.
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.
busfran) Lope is a result of the intake and exhaust valves both being open at the same time. This is called overlap. Mild cams have little or no overlap at any valve opening that makes a difference. Hotter aftermarket type cams have a lot because it aids high RPM breathing.
The camshafts have the job of opening the valves that let air into and exhaust out of the engine. The camshaft uses rotating lobes, called cams, that push against the valves to open them.
jz78817 , 05-04-2014 08:50 PM. back in the day (like, way back[/i]) having a V8 with a lopey idle meant you had a hot camshaft (long duration/overlap) in it. now that we have variable cam timing, it's mostly for show.
Overlap can be calculated by adding the exhaust closing and the intake opening points. For example, a cam with an exhaust closing at 4 degrees ATDC and an intake opening of 8 degrees BTDC has 12 degrees of overlap.
Locate the ID number on the camshaft. It is typically located in the center of the cam between the lobes. The ID number will consist of either eight or nine digits; the last four numbers identify the cam and its specific application. Match the number to a Chevrolet camshaft part number listing.
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).
One way to improve the low-speed torque on a camshaft with too much duration is to advance the intake lobe in relation to the exhaust. Advancing just the intake lobe opens and closes the intake valve sooner which is one way to help improve the low-speed torque.
To advance or retard a camshaft is to change the alignment between the camshaft and the crankshaft. Advancing or retarding the cam pushes the centerline of the camshaft to one side or the other of the crankshaft centerline.
A Basic Overview of Cam Timing
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.A performance camshaft
is just a camshaft whose lobe profile is tailored to utilize more of an engine's potential. usually a higher lift on the lobe, which increases in length of the valve stroke, which allows for more air to enter through the inlet valves, increasing the power potential of the engine.Intake Cams will have the most noticeable effect on engine performance. Intake Duration determines how much time the engine has to take a breath of fresh air/fuel. In general, shorter duration will increase low RPM torque and longer duration will increase high RPM horsepower.
Timing in the Camshaft. Rotate the crankshaft clockwise to 90 degrees after TDC. This will make sure all the pistons are half way down the bore. Now position the dial gauge so that it can read the lift of the inlet valve of number 1 cylinder from the top of the valve retainer (see left).
Cam timing is VALVE timing. Ignition timing is SPARK timing. If your engine likes 36 degrees of total timing, then that's where you set the timing at, whether the cam is 2 degrees retarded, 4 degrees advanced, or straight-up, it makes zero difference because neither have anything to do with each other.
Short duration cams are good for low speed torque and throttle response while long duration cams are best or high revving engines that need to make lots of top end power. A cam with a duration of 240 degrees of higher will typically produce the most power from 3,500 to 7,000 rpm.
A camshaft can boost your horsepower since they can increase the amount of time or duration a valve remains open. Increased duration results in increased airflow. The more air flows through the engine, the more horsepower is generated.
It is listed in degrees of crankshaft rotation. When someone refers to a "big cam," they mean it has longer duration, not higher Lift. Duration at 0.050" is the degrees of crankshaft rotation between when the lifter is raised 0.050" and when it is 0.050" from its resting position.
Find the profile or grind number. This number should be on your camshaft, followed by a number of degrees. For example, you might have a camshaft stamped with the numbers 899C, followed by various numbers with degrees. Take the 899C and add it to the model prefix.
A performance camshaft
is just a camshaft whose lobe profile is tailored to utilize more of an engine's potential. usually a higher lift on the lobe, which increases in length of the valve stroke, which allows for more air to enter through the inlet valves, increasing the power potential of the engine.DURATION: Duration is how long the cam holds the valves open. 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.
The two don't necessarily need to be used together. Roller camshafts and lifters can be used in an engine that features nonroller rockers; by the same token, roller rocker arms can be used in an engine that features a flat-tappet solid or hydraulic camshaft.
