The camshaft selector guide for beginners involves understanding the critical points for correcting “camfusion,” which is the process of selecting the right camshaft for your engine. There are many variables that will affect how a camshaft will perform in your engine, and it’s important to understand camshaft design at a fundamental level before diving into the numbers.
Camshaft Selection Explained
- Lift: Most street performance cams will range between .450 and .550-inches of lift. However, as you move to more radical profiles, say .460-inches and up, you’ll need to consider your budget and the necessary upgrades to the valvetrain components.
- Valvetrain Upgrades: High lift camshafts will require an upgrade to the original valve springs, rocker arms, and pushrods to prevent issues like coil bind, changes in clearance, or part failure.
- Engine Compatibility: If you have power brakes that require vacuum at idle or a stock transmission and converter, a high lift cam may not be the best choice.
- Mild Street Cam: On a near-stock engine, a camshaft around .450-inches of lift, 110 degrees of lobe separation, and .218 duration at .050-inch lift should provide a choppy idle while maintaining strong vacuum.
- Importance of Vehicle Characteristics: The right camshaft involves much more than just matching valvetrain components. The entire sum of the vehicle, including the transmission, torque converter, weight, compression ratio, tire size, and rear-end gear ratio, will all affect the rpm characteristics.
- Manufacturer Recommendations: Most camshaft manufacturers will list the optimum rpm range on each camshaft, but you should also consider your intentions for the car.
Expert Cam Recommendations
We consulted our tech experts at Speedway and asked for their recommendations on a ’32 Ford street rod and a ’55 Chevy.
’32 Ford Street Rod
- Engine: 350 cubic-inch, 9:1 compression
- Transmission: TH350, 2200rpm stall
- Rear Gear Ratio: 3.50:1
- Weight: 2800lbs
- Recommended Cam: Comp 260H grind, .440-inch lift, 212-degrees duration at .050-inch lift, 110 degrees of lobe separation
’55 Chevy
- Engine: 383 cubic-inch, 10.5:1 compression
- Transmission: TH350, 3000-3500rpm stall
- Rear Gear Ratio: 4.11:1
- Weight: 3,350lbs
- Recommended Cam: Comp 292H grind, .501-inch lift, 244 duration at .50-inch lift, 110 degrees of lobe separation
Camshaft Type
The type of camshaft you choose will also affect the selection process:
| Camshaft Type | Gear Type |
|---|---|
| Cast Iron Hydraulic or Solid Flat Tappet Cam | Cast Iron Gear Composite Gear |
| Austempered Ductile Iron Hydraulic or Solid Roller or Nitrided Cam | Melonized / Hardened Steel Gear Composite Gear |
| Billet Steel Hydraulic or Solid Roller Cam | Bronze Gear Composite Gear |
Camshaft Duration
- Camshaft Duration is the measurement of the time one valve begins to open until it finishes closing.
- Duration is measured in degrees of crankshaft rotation, not camshaft rotation.
- You’ll see camshaft duration listed in two ways: advertised duration and duration at .050-inch tappet lift.
- Advertised duration is the time between when the camshaft lobe first starts to open the valve and when it last closes the valve.
- Duration at .050-inch tappet lift is the time between when the valve begins to open and when it finishes closing, measured at .050-inch tappet lift.
Camshaft Selector Guide DIY
- If you’re having your engine assembled by a professional, involve their opinions and knowledge in the selection process.
- The most common mistake is selecting a cam that is too big, which can hurt performance.
- If you’re deciding between two camshafts, the smaller grind is typically the wise choice.
- Pay close attention to two key elements advertised by camshaft manufacturers:
- RPM Band: Match the RPM band closely with the intended use of the engine. Street cars will spend more time at low RPM, so an idle-5,500 or 1,500-6,500 range would be best. Race cars that spend most of their time in the upper ranges may prefer 2,500-7,000 RPM or 3,500-8,000 RPM.
- Characteristics Description: Most cam manufacturers provide a 2-3 sentence description of the camshaft’s best uses and performance characteristics, which can be helpful “cliff notes” for selection.
Camshaft Selector Guide Explained for Beginners
The camshaft selector guide for beginners involves understanding the critical points for correcting “camfusion,” which is the process of selecting the right camshaft for your engine. There are many variables that will affect how a camshaft will perform, and it’s important to understand camshaft design at a fundamental level before diving into the numbers. Once you have a better understanding of how each specification affects engine performance, selecting the right camshaft becomes less of a guessing game and more of a knowledge-based decision. The right camshaft involves much more than just matching valvetrain components – the entire vehicle, including the transmission, torque converter, weight, compression ratio, tire size, and rear-end gear ratio, will all impact the rpm characteristics. By considering all these factors and consulting expert recommendations, you can make an informed choice on the best camshaft for your build.
Reference:
– How to Pick the Right Camshaft
– Camshaft Selection Explained
– Understanding Cam Lobe Fundamentals: A Guide for Beginners
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