Camshaft Selection Small-Block Chevy

Article by Mark Trotta

Before computer-controlled engines, the 'brain' of the engine was the camshaft.

Factors when choosing a cam should include engine size and compression, cylinder heads and valve size, transmission type, and vehicle weight.

Camshaft In Operation

The lobes on a camshaft push against the push rods and rocker arms to open the valves as the camshaft rotates. The valve springs push them closed on their return. In proper sequence, these series of events produce an efficient and strong-running engine.

The best camshaft for your application will allow all engine components to work well together (carb, manifold, exhaust, etc).

Lift

To a point, the further the valve rises from its seat the more airflow can be released. At very high RPM, valve bounce may result. This happens when valve spring tension is insufficient to keep the valve following the cam at its apex. Too high a lift may also cause interference with the valve head and the top of the piston.

Duration

Duration is the number of crankshaft degrees of engine rotation during which the valve is off it's seat. As you increase the duration of the cam, you increase the peak horsepower, but at the expense of low end torque. Do not overdo the duration when selecting a camshaft. Over-camming is an all-too-common common mistake when building a street motor.

Because different measuring points are used for advertised duration, the industry established .050" of tappet lift as a common measuring point, allowing cams from different companies could be accurately compared.

If you can't decide between two cams, choose the milder one.

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Single Pattern vs Dual Pattern

Camshafts were originally designed with the same duration and lift on both the intake and exhaust lobes. These are referred to as single-pattern cams.

Through the years, cam manufacturers have found that many engines prefer more duration on the exhaust lobe than on the intake lobe. These are called dual-pattern cams.

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Edelbrock 2102 Camshaft Kit

Here's one of Edelbrock's mid-performance cams for 1957-1986 Chevy small-blocks. The 2102 cam optimizes low to mid-range torque from off-idle to 5500 rpm. It features smooth idling for daily driven cars and light trucks.

As you can see from the dyno chart results, there is an increase in throttle response and torque.

Edelbrock 2102 Cam Specs

The 2102 cam kit includes camshaft, hydraulic lifters, assembly lube and instructions. It is to be used with stock ratio rocker arms only. Fits 1957-1986 small-block Chevy 283-400 V-8's and is 50-state legal.

Shop: Edelbrock 2102 Camshaft Kit

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Edelbrock 7102 Camshaft Kit

From Edelbrock's "Performer Plus" series, the 7102 cam features a more aggressive profile than the 2102 cam. It is designed to increase horsepower and torque from idle to 6,500 rpm.

This is a good cam for high performance street use. It's also dyno-matched to Edelbrock's Performer line of intake manifolds.

Edelbrock 7102 Cam Specs

Shop: Edelbrock 7102 Camshaft Kit

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1970 Chevelle SBC Camshaft Selection

When I bought my old 1970 Chevelle, the engine had been modified with a slew of aftermarket pieces installed by the former owner. It made great power after 3,000 rpm, but was sluggish at lower RPMs.

Since the car was to used as a daily driver, I needed to bring performance back to a streetable level. I took out a 350 horsepower cam and installed a 300 horsepower cam, along with new timing chain and gears.

Also removed was a single-plane intake manifold and double-pumper carburetor, replaced with a dual-plane manifold and Holley 1850 carburetor.

These changes made the Chevelle a good daily driver, and still made enough power for occasional bursts of "spirited" driving.

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Related Articles:

Best Heads For Gen-1 SBC

1970 Chevelle Restoration

1966 Corvette Project

327 Chevy Camshaft Installation

Gen 1 Cylinder Head Assembly and Installation

Install and Adjust Push Rods and Rocker Arms

SBC Timing Chain, Gears, and Cover

Best Oil for Classic Cars

Best Engine Assembly Lube

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NHRA Stock Eliminator Winner

Back around 2010, Wade Owens of Cape Girardeau, Missouri, ran a 283ci motor in a 1966 Chevelle, and successfully competed in NHRA's Stock Eliminator class. Duration on his cam was about 258/260 degrees at 0.050 inch, and lift for this engine combination was rules-limited to 0.399 inch, measured at the retainer.

With this relatively mild camshaft, Wade's Chevelle consistently ran in the mid-11s, which was at or under the national Stock Eliminator class record.

Read More about Wade here: Drag Central "Horsepower Happy"

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