1. What is Camshaft Arm Ratio?

The camshaft arm ratio (also called rocker arm ratio) is the mechanical advantage provided by the valve train components. It determines how much the valve opens relative to the camshaft lobe lift.

2. How Does the Calculator Work?

The calculator uses the simple ratio formula:

Where:

• \( Valve\ Lift \) — Maximum valve opening distance (mm)
• \( Cam\ Lift \) — Maximum camshaft lobe height (mm)

Explanation: The ratio shows how much the rocker arm multiplies the camshaft's motion to open the valve.

3. Importance of Ratio Calculation

Details: Knowing the ratio is essential for engine builders to properly select camshafts and predict valve train behavior. It affects valve timing, spring requirements, and overall engine performance.

4. Using the Calculator

Tips: Measure both valve lift and cam lift accurately in millimeters. Typical ratios range from 1.1:1 to 1.8:1 in most engines.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical rocker arm ratio?
A: Most production engines use ratios between 1.5:1 and 1.7:1, though this varies by engine design.

Q2: Can changing the ratio affect engine performance?
A: Yes, increasing the ratio can improve airflow but may require stronger valve springs and can increase wear.

Q3: How do I measure valve lift accurately?
A: Use a dial indicator on the valve retainer while rotating the engine through full cam rotation.

Q4: Does ratio affect valve timing?
A: While it doesn't change cam timing directly, it affects the rate at which valves open and close.

Q5: Can I use this for overhead cam engines?
A: Yes, though many OHC engines use direct-acting buckets with a 1:1 ratio.