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This permits the cylinder to begin building pressure sooner and that boosts low-speed torque.

A larger angle yields less valve overlap (the period when both valves are open at the same time). In terms of engine performance, the lobe center angle is significant. Note that 0.050-inch tappet lift equals 0.050 times the rocker ratio to indicate valve lift at the checking point. In addition to lift duration and overlap, it also indicates the intake and exhaust centerlines, lobe separation angle, and the location of timing events relative to the four cycles. This illustration tells you everything you need to know about camshaft operation. When you do this you are effectively moving the intake lobe centerline closer to or farther from TDC. The lobe centerline can be altered by advancing or retarding the cam. Lobe center angle is fixed and cannot be changed after the cam is ground.

To avoid confusion when comparing cams, remember that the lobe center angle is measured between the centerlines of the intake and corresponding exhaust lobes, while lobe centerline is the angle measured between the center of the lobe and TDC.

This is the geometric centerline of that particular lobe. Imagine a line passing from the center of the cam directly through the highest point on the cam lobe. As the cam rotates, the lifter moves up the flank of the lobe and over the top to open the valve. Intake Valve Closes – Compression Stroke b) The basic cam lobe shape is an eccentric with the lifter riding on the base circle. You can copy and paste this link to share: Ī) A. SHARE THIS ARTICLE: Please feel free to share this article on Facebook, in Forums, or with any Clubs you participate in. For a comprehensive guide on this entire subject you can visit this link: LEARN MORE ABOUT THIS BOOK HERE

This Tech Tip is From the Full Book, PERFORMANCE AUTOMOTIVE ENGINE MATH. This chapter looks at the basic calculations relating to camshafts and valvetrain components and how you can use them to equip and tune your particular combination for top performance. Most enthusiasts have a basic understanding of the cam, lifter, pushrod, rocker arm, and valve relationship, but keeping all the numbers straight is often intimidating. There’s lift and duration, overlap and lobe centers, lobe separation angles and so on, and all of them have numbers attached. Camshafts are a subject that all car guys love to talk about, and those who listen tend to roll their eyes at the staggering number of terms and numbers.