1. What is Rocker Arm Valve Ratio?

The rocker arm valve ratio is the mechanical advantage provided by the rocker arm in an engine's valvetrain. It determines how much the valve opens relative to the camshaft lift.

2. How Does the Calculator Work?

The calculator uses the valve ratio formula:

Where:

• \( \text{Valve Lift} \) — Maximum lift at the valve (mm)
• \( \text{Cam Lift} \) — Maximum lift at the cam lobe (mm)

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

3. Importance of Valve Ratio

Details: Valve ratio affects engine performance by determining valve timing and lift. Higher ratios can increase airflow but may require stronger valve springs.

4. Using the Calculator

Tips: Measure 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, while performance engines may use higher ratios.

Q2: Can I change my rocker arm ratio?
A: Yes, by installing different ratio rocker arms, but this affects valve timing and spring requirements.

Q3: How does ratio affect engine performance?
A: Higher ratios increase valve lift and duration, potentially improving high-RPM power but may reduce low-end torque.

Q4: Does ratio affect valve spring pressure?
A: Yes, higher ratios increase the load on valve springs as they multiply both motion and forces.

Q5: How do I measure valve and cam lift?
A: Valve lift is measured at the valve stem, cam lift is measured at the lifter or pushrod (before the rocker arm).