1. What is Rocker Arm Ratio?

Rocker arm ratio is the mechanical advantage provided by a rocker arm in an internal combustion engine. It determines how much valve lift is achieved relative to camshaft or pushrod movement.

2. How Does the Calculator Work?

The calculator uses the rocker arm ratio formula:

Where:

• Lift at Valve — Maximum valve lift measurement (inches)
• Lift at Pushrod — Corresponding pushrod/camshaft lift measurement (inches)

Explanation: The ratio represents the mechanical multiplication factor between the camshaft/pushrod movement and the actual valve opening.

3. Importance of Rocker Arm Ratio

Details: Understanding rocker arm ratio is crucial for engine builders and tuners as it affects valve timing, engine performance, and camshaft selection. Higher ratios provide more valve lift from the same cam profile.

4. Using the Calculator

Tips: Enter both lift measurements in inches. Ensure measurements are taken at the same reference points for accuracy. Typical rocker arm ratios range from 1.5:1 to 1.8:1 in most production engines.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical rocker arm ratio?
A: Most production engines use ratios between 1.5:1 and 1.7:1, while performance engines may use ratios up to 1.8:1 or higher.

Q2: How does rocker ratio affect valve lift?
A: A higher ratio increases valve lift without changing the camshaft profile, potentially improving airflow and engine performance.

Q3: Can I change rocker ratios in my engine?
A: Yes, many engines allow aftermarket rocker arms with different ratios, but this may require additional modifications and clearancing checks.

Q4: Does rocker ratio affect valve timing?
A: While the ratio primarily affects lift, it can slightly alter valve timing characteristics and should be considered in camshaft selection.

Q5: How do I measure lift accurately?
A: Use a dial indicator at both the valve tip and pushrod end, measuring maximum lift during cam rotation.