Edelbrock Performer Camshaft Timing Degrees
Edelbrock offers two camshafts in the "Performer" family--the Performer-Plus and the Performer RPM--for AMC, Buick, Chevrolet, Chrysler, Ford, Oldsmobile and Pontiac engines. (Only the Performer-Plus is available for the Buick engine.) The valve-timing events of the Performer-Plus cams are designed for good off-idle through 5500 rpm performance, while the Performer RPM series use lobe profiles that extend the range to 6500 rpm for higher performance.
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How Lobe Design Affects Engine Performance
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Camshaft lobes are designed with specific, precise eccentrics (a "rise" outside the base circle of the lobe) to impart an opening and closing event of the intake or exhaust valves. This controls the distance the valves open, the duration--in crankshaft degrees--they are open, and the "shape" (exactly when and how) of their movement.
Typical production cams are designed to open valves a moderate distance for a short period of time. Reliability and acceptable low engine-speed performance are the goal of standard-duty cams. By modifying the shape of the lobe, the valve-events can be improved resulting in greater potential power output. Along with the cylinder heads and induction system, camshaft design is one of the most critical factors in how the engine "behaves".
Duration and Engine RPM Range
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Duration is the length of time a valve is open, and most frequently noted as "advertised" and "@ .050-inch lift" specifications. Advertised durations are less-absolute values because manufacturers can measure them at different points of movement. The duration at .050-inch lifter-rise is a standard and certain point by which to compare one camshaft with another.
Most standard production cams have "@ .050" durations in the 200 to 210 degree range. These are considered "short" durations and offer good low-rpm performance. By lengthening the duration, the valve is open longer and the power output of the engine moves higher in the rpm range. As a general rule, a 10-degree increase in duration moves the power range higher by 500 rpm.
As an aside, one of the next most important specs of a cam lobe is the lift, or the distance it opens the valve. Through the combination of all lobe factors (duration, lift and lobe separation angle, among others), more air/fuel mixture can be introduced into the cylinder.
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Performer-Plus Camshaft Timing
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This series of Edelbrock camshaft is designed for improved performance over a factory production cam. They provide increased torque and horsepower by increasing the duration beyond the factory grind by 5 to 10 degrees, thereby moving the powerband of the engine up a few hundred rpm. Across nearly all engine families, the Performer-Plus grinds commonly have 204 to 214 degrees of duration at .050-inch lift.
The exceptions are for the larger displacement engines--400 cubic inches and up--which can have as much as 218 to 228 degrees of duration. (Larger engines require a more duration to provide more air and fuel.)
Total valve lift is slightly larger than stock.
Performer RPM Camshaft Timing
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To move the powerband up 1000 rpm, the Performer RPM cams add an additional 20 degrees of duration to the valve-events. Using the small-block Chevy engine as an example, the Performer RPM durations are 234 and 244 degrees for intake and exhaust valves, respectivel,y while they are 204 and 214 degrees for the Performer-Plus grind. (The total valve lift is also between 10 and 15 percent greater on the RPM series compared to the Plus series.)
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