1. What is Rocker Arm Ratio?

The rocker arm ratio is the mechanical advantage provided by the rocker arm in a valve train system. It determines how much the valve lift is multiplied compared to the camshaft lift.

2. How Does the Calculator Work?

The calculator uses the rocker arm ratio formula:

Where:

• \( Valve\ Lift \) — Maximum lift at the valve (mm)
• \( Cam\ Lift \) — 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 Rocker Arm Ratio

Details: The rocker arm ratio affects engine performance by determining valve lift and duration. Higher ratios increase valve lift without changing the camshaft profile.

4. Using the Calculator

Tips: Enter valve lift and cam lift in millimeters. Both values must be positive numbers for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical rocker arm ratio for small engines?
A: Most small engines have ratios between 1.1:1 to 1.8:1, with 1.5:1 being common.

Q2: Can changing rocker arms affect engine performance?
A: Yes, higher ratio rocker arms increase valve lift and can improve airflow, but may require valve spring upgrades.

Q3: 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).

Q4: Are there limitations to increasing rocker arm ratio?
A: Excessive ratios can cause valve train instability, increased wear, and may require modifications to avoid piston-to-valve contact.

Q5: Does rocker arm ratio affect valve timing?
A: While it doesn't change the cam's timing events, it can affect the effective duration as seen at the valve.