1. Typical Stock Cam Setup
With the throttle plate closed on a stock engine/camshaft setup, approximately 15.0 inHg of vacuum is created, which helps the brake booster function normally.
2. Big Cam Setup
When big camshafts are installed, vacuum can drop to the 1.0-3.0 inHg range. This is not enough vacuum to assist the brake booster. The result is heavy pedal pressure and poor brake function.
3. Any Vacuum Setup with a Vacuum Pump
With the vacuum pump and vacuum switch installed, vacuum pressure is maintained between 18-22 inHg, regardless of the camshaft being used. Normal or improved brake pedal effort and function result.