Adjusting the rocker arm ratio is a technical modification that increases valve lift without replacing the camshaft. Increasing valve lift can improve engine breathing, but requires engine knowledge and can lead to performance losses if not done correctly. The ratio is adjusted by installing a rocker arm with a higher ratio or by adjusting the rocker arm itself, which increases valve travel and can improve engine performance.

Example: The original ratio is 1/1.15, so with 7mm of cam lift, you have 8.05mm of (theoretical) valve lift. Now the ratio is 1/1.2, so with 7mm of cam lift, you now have 8.4mm of (theoretical) valve lift. Multiply this by the effective surface area of your valve.