1. What is Rocker Arm Ratio?

The Rocker Arm Ratio is a mechanical measurement that describes the relationship between the input and output arms of a rocker mechanism. It determines the mechanical advantage and valve lift in engine valve trains.

2. How Does the Calculator Work?

The calculator uses the simple ratio formula:

Where:

• \( Y \) — Output arm length (distance from pivot to valve contact point)
• \( X \) — Input arm length (distance from pivot to pushrod contact point)

Explanation: The ratio indicates how much the input motion is multiplied at the output. A higher ratio means greater valve lift for a given camshaft lift.

3. Importance of Rocker Arm Ratio

Details: Proper rocker arm ratio is crucial for engine performance, valve timing, and preventing valve train component failure. It affects valve lift, duration, and overall engine efficiency.

4. Using the Calculator

Tips: Measure both Y and X distances accurately in the same units (inches or millimeters). Both values must be greater than zero for valid calculation.

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 2.0:1 or higher.

Q2: How does rocker ratio affect valve lift?
A: Valve lift = Cam lift × Rocker ratio. Higher ratios increase valve lift without changing the camshaft.

Q3: Can I change rocker ratios on my engine?
A: Yes, but it requires careful consideration of valve train geometry, spring pressures, and piston-to-valve clearance.

Q4: How do I measure rocker arm ratio?
A: Measure from the pivot center to the pushrod cup center (X) and from the pivot center to the valve tip contact point (Y).

Q5: What are the limitations of changing rocker ratios?
A: Higher ratios increase valve train stress, may require stronger components, and can affect valve timing and duration characteristics.