Installing a performance camshaft, or "camming" a car, primarily increases high-RPM horsepower and torque by improving engine breathing, resulting in a distinct choppy idle. However, this modification typically reduces low-speed driveability, decreases fuel efficiency, and requires supporting upgrades like an ECU tune for optimal performance.
Replacing the stock camshaft with a performance camshaft alters valve timing and lift. This allows more air and fuel into the combustion chamber, significantly boosting power output at higher engine speeds. Industry dynamometer data indicates that a properly selected performance cam can increase horsepower by 10-25% in the upper rev range, depending on the engine and supporting modifications. The trade-off is a noticeable loss of low-end torque, which can make the car feel sluggish during city driving or acceleration from a stop.
The characteristic choppy idle or "lope" is a direct result of increased valve overlap—the period when both intake and exhaust valves are open simultaneously. This design improves high-RPM exhaust scavenging but causes uneven cylinder filling at idle, creating the rhythmic sound. It is a normal operational effect, not a misfire. However, excessive overlap can lead to rough idling, potential stalling, and increased emissions.
To harness the power gains and maintain reliability, several supporting modifications are essential. A custom ECU tune is non-negotiable to recalibrate air-fuel ratios and ignition timing. Without it, the engine may run poorly or sustain damage. For higher-lift cams, upgrading to stronger valve springs and pushrods is often necessary to prevent valve float at high RPMs, a failure point noted in aftermarket performance builds.
Daily driveability is frequently compromised. A aggressive cam profile can make smooth low-speed maneuvering challenging and often leads to a fuel economy reduction of 15-30%, as observed in real-world user reports. Emissions compliance is another critical hurdle. In regions with strict standards like California's CARB, most performance cams are not certified, potentially failing smog tests and rendering the vehicle illegal for street use.
The decision to cam a car hinges on intended use. For dedicated race applications, the high-RPM power benefits are substantial. For a street-driven vehicle, the sacrifices in comfort, efficiency, and legality must be weighed carefully. Successful installations rely on a holistic approach, pairing the cam with complementary intake, exhaust, and tuning work to create a balanced and functional package.
