Summit Racing™ Street Vacuum Pumps

KEY POINTS SUMMARY

• Engines with aggressive camshaft profiles can have insufficient manifold vacuum for power-assisted brakes

• Mild street engines generally have 17-23 in.Hg of vacuum, and power brakes require 16-17 in.Hg

• Summit Racing street vacuum pumps plumb between the engine and brake booster, supplying 20-23 in.Hg of vacuum on demand for safe, reliable brake performance

• Summit vacuum pumps are 12V diaphragm or rotary vane units, and many include hose, wiring, and installation hardware

High-lift, long-duration cams with tons of overlap are great. They help your engine make big horsepower and give you the loping, choppy idle that every gearhead loves. They do have a drawback, though, and it’s a big one: low manifold vacuum that can make power brakes dangerously ineffective. Fortunately, Summit Racing vacuum pumps are a simple solution to a serious problem.

How Vacuum Assisted Brakes Work

The mildly tuned engine in a typical daily driver makes around 18-22 in.Hg of manifold vacuum at idle. This gets stored in the vacuum booster located behind the brake master cylinder, multiplying the force at the brake pedal when the brakes are applied, referred to as vacuum assist. During every brake application, vacuum is used and immediately replenished by the engine’s manifold vacuum. A minimum of 16-17 in.Hg of vacuum is necessary for proper power brake operation.

The Problem with Aggressive Cams and Low Manifold Vacuum

In the case of the high-performance vehicles we all love, an aggressive camshaft can easily reduce vacuum below what’s required for power brakes to function safely, sometimes into the single-digit range. A single-plane intake manifold can make the problem worse.

Vacuum Pump Installation

Summit’s vacuum pumps are plumbed into the vacuum line between the engine and the brake booster. That way, you get to use whatever the vacuum the engine makes, plus the vacuum created by the pump. Summit vacuum pumps make 20-23 in.Hg—exactly what your power brakes need! They’re also automatic, only running when vacuum is depleted. They require 12V DC, and are simple to wire in.

Summit Racing street vacuum pumps are available in both diaphragm and rotary vane styles, and many include hose, wiring kits, and mounting hardware.

FAQ SECTION:

Q. What does a brake vacuum pump do?

A. A brake vacuum pump creates a vacuum supply for the brake booster. This allows power-assisted brakes to function properly.

Q. What happens when a brake vacuum pump fails?

A. If a brake vacuum pump fails, vacuum assist is reduced to whatever the engine can provide on its own (this amount varies by vehicle). The brake pedal will require more force for sufficient braking.

Q. Why does my brake pedal go to the floor, but the fluid reservoir is full?

A. This could happen for a few reasons, and none of them are related to brake vacuum assist. Typically, when you don’t have enough vacuum, the pedal is hard; not soft. Reasons the pedal is going to the floor with a full reservoir include air in the brake hydraulics, a faulty master cylinder, or even drum brakes that are out of adjustment (this won’t generally cause the pedal to go to the floor, but it can cause excessive pedal travel). Badly rusted pad backing plates and rotors, and pads stuck in the carriers can also contribute to excessive pedal travel.