Cammed Cars: What The Term Means And Why People Do It

Back in the days before variable valve timing (VVT) and computer-controlled engine tuning, one of the best ways to improve stock engine performance was to install an aftermarket camshaft, a process referred to as "camming" a car. But don't get different parts like camshaft and crankshaft confused. Even though changing either (or both) can improve engine performance, they're two entirely different projects. Replacing the crankshaft in an engine with a longer-stroke crank creates a stroker engine with a higher displacement than the stock version.

While building a stroker engine requires removal and a complete teardown of the car's engine along with some precision machining, you can often cam an engine by simply removing components in front like the radiator and belt-driven accessories. While removing the cylinder heads can make the job even easier, replacing the stock camshafts in single and double overhead cam (SOHC and DOHC) engines is a simpler task than with the centrally-located camshafts in pushrod engines.

An engine's camshaft has egg-shaped lobes that act as ramps to open the intake and exhaust valves. Stock cams typically have a modest profile designed to time the intake and exhaust strokes with a bias toward efficiency and quiet performance. Replacing the stock camshaft provides an opportunity to install a cam with a more aggressive profile delivering higher horsepower levels.

The primary reason for camming a car engine is to gain improved performance. For example, upgrading the cam in a third-generation 5.7 HEMI can provide gains of around 67 horsepower. Secondary to these power increases is the symphony of new sounds that emanate from the engine thanks to the new high-performance aftermarket cam. Camming a car can change the rhythm, tone, and volume of your car's exhaust sound. To better explain what a more aggressive cam does, we'll describe the profile of each of a camshaft's lobes in terms of degrees of rotation for which it holds the valves open, and the distance they open in inches.

For example, the GM Performance 350 HO Deluxe crate engine is rated at 330 horsepower. While there are other important specifications, the included camshaft (P/N 24502476) holds the intake valves open at least 0.05 of an inch for 212 degrees and keeps the exhaust valves open through 222 degrees of rotation. It also provides 0.435 of an inch of lift to the intake valves and 0.46 of an inch to the exhaust valves with 1.5:1 rocker arms. In comparison, GM Performace's SP383 Deluxe crate engine, a 383 stroker engine, provides 435 horsepower thanks in part to its camshaft. That camshaft, P/N 19210723, provides 222 degrees of intake and 230 degrees of exhaust valve opening at a minimum of 0.05 of an inch. With the same 1.5:1 ratio rocker arms, the cam provides 0.509 inches of lift to the intake valves and 0.528 inches of lift to the exhaust valves.

Whether your camming a car for increases in intake or exhaust capabilities (or both), we'd be remiss not to mention the potential downsides. When automakers design an engine to power their cars (even performance-oriented versions) they do their best to find the sweet spot between performance, fuel efficiency, and drivability. Installing a high-performance cam in your car tilts the equation toward performance, usually to the detriment of the other two factors. While you might see an improvement in your car's performance in higher rev ranges, camming a car often results in a loss of low-rpm torque and reduction in fuel mileage.

Replacing your engine's camshaft can also change its emissions levels, potentially putting you afoul of your area's standards. For example, California residents must use a California Air Relations Board (CARB)-compliant upgrade when camming their cars. Camming your car might also be a violation of your warranty, so carefully read any relevant documentation before swapping your cam.