Camshafts are the heart of an engine’s valve train, responsible for precisely controlling the opening and closing of the intake and exhaust valves. Understanding the intricate details of camshaft design and performance is crucial for anyone seeking to optimize the power and efficiency of their vehicle. In this comprehensive guide, we’ll delve into the measurable and quantifiable data that defines the critical aspects of camshafts in cars.
Cam Lobe Tolerance: Precision at the Micron Level
The tolerance of cam lobe grinding is a testament to the advancements in modern manufacturing techniques. Today’s camshafts are typically ground to a tolerance within 10-50 millionths of an inch (.000010″-.000050″), a level of precision that can only be achieved through the use of state-of-the-art CNC (Computer Numerical Control) machines. This tight tolerance ensures that the cam lobes are perfectly shaped, minimizing any potential for power loss or valve train issues.
Lobe Separation Angle (LSA): Balancing Valve Overlap
The Lobe Separation Angle (LSA) is a crucial parameter that affects the overlap between the intake and exhaust valves. This angle, expressed in camshaft degrees, plays a significant role in determining the engine’s power characteristics. For instance, a Summit Racing Pro LS series camshaft may have an LSA of (108 + 116) / 2 = 112 degrees, which is a common configuration for high-performance LS engines.
Lobe Lift: Measuring Valve Travel
Lobe lift is the vertical distance the valve travels from its closed position, and it is typically expressed in inches. This measurement can be taken at different points, such as at the valve face or at the lobe peak, providing valuable insights into the cam’s ability to effectively control valve movement.
Duration: Timing the Valve Events
Duration is the amount of time, measured in crankshaft degrees, that the valve is off its seat. This parameter is typically measured at 0.050″ lift and is a critical factor in determining the power characteristics of an engine. Precise duration tuning can help optimize an engine’s performance across a wide range of rpm.
Intake Centerline: Determining Camshaft Advancement
The intake centerline is the crankshaft degree position where the intake valve reaches its maximum lift. This measurement plays a crucial role in determining the camshaft’s advancement, which can significantly impact the engine’s power delivery and efficiency.
Mechanical Valve Lash: Maintaining Proper Clearance
Mechanical valve lash is the clearance between the rocker arm and the valve tip, measured with feeler gauges when the engine is at full operating temperature. This clearance must be measured when the cam lobe is on the base circle, as it ensures the proper valve train geometry and prevents potential issues such as valve float or premature valve train wear.
Lobe Angle: Controlling Lifter Velocity
The lobe angle affects the speed at which the lifter can be raised. For example, a stock Chevy 0.842 diameter lifter has a maximum velocity of 0.00700 inch per degree, while a Ford 0.875 lifter can reach 0.00735 inch per degree. Careful consideration of lobe angle is essential to prevent excessive lifter velocity, which can lead to premature wear or even catastrophic failure.
Advertised Duration vs. Duration at 0.050″
It’s important to understand the distinction between advertised duration and duration at 0.050″. Advertised duration is the duration measured at the lobe’s maximum lift, while duration at 0.050″ is measured when the lifter is 0.050″ off the seat. This difference in measurement points can provide valuable insights into the cam’s overall performance characteristics.
By mastering these technical details, enthusiasts and professionals alike can make informed decisions when selecting, tuning, and maintaining camshafts for their high-performance engines. Understanding the nuances of camshaft design and analysis is the key to unlocking the full potential of any engine.
References:
– Camshaft Art and Science: You Get Out What You Put In
– How to Read a Cam Card to Understand Camshaft Specs
– Camshaft Design Science
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