A cam, short for camshaft, is a rotating shaft inside your car's engine that acts like a precise choreographer for the engine's valves. Its primary job is to open and close the intake and exhaust valves at the exact right moment. This allows fresh air and fuel to enter the cylinders and lets exhaust gases escape after combustion. Without a camshaft, the engine's valves wouldn't open, and the engine simply couldn't run.
The camshaft is located in the cylinder head and is driven by a timing belt or chain connected to the crankshaft. Along the shaft are egg-shaped lobes, which are the actual "cams." As the shaft rotates, the high point of each lobe presses against a component (like a lifter or follower), which then pushes the valve open. When the lobe rotates away, a spring closes the valve. The specific shape and orientation of these lobes—a design known as the camshaft profile—directly influence the engine's character. A profile designed for low-end power will differ from one optimized for high-RPM performance.
There are common configurations, such as Single Overhead Cam (SOHC) and Double Overhead Cam (DOHC). DOHC engines, often found in performance vehicles, use two camshafts per bank of cylinders—one for intake valves and one for exhaust valves—allowing for more precise control and better airflow, especially at high speeds.
| Engine Configuration | Typical Number of Camshafts | Key Characteristics |
|---|
| Inline-4 (SOHC) | 1 | Simpler, more compact, cost-effective. |
| Inline-4 (DOHC) | 2 | Better for high-RPM power, allows for variable valve timing. |
| V6 (DOHC) | 4 | High performance, complex, common in sports sedans and SUVs. |
| Pushrod (e.g., V8) | 1 | Compact design, excellent low-end torque, simpler valve train. |
A related advanced technology is Variable Valve Timing (VVT). This system allows the camshaft to change its timing relative to the crankshaft, optimizing valve operation for both power and efficiency depending on engine speed. In short, the camshaft is a fundamental component that dictates engine breathing, directly impacting power delivery, fuel economy, and emissions.
