How To Install An Electric Vacuum Pump On Your Hot Rod

In The Garage Media published "How To Install An Electric Vacuum Pump On Your Hot Rod" by Brian Brennan on August 31, 2022. The story follows the installation of the Granatelli Motor Sports 12V Electric Vacuum Pump Kit on a hot rod and explains why many performance engines need help making vacuum.

Why a Hot Rod Can Run Short on Vacuum

According to the article, power brakes, wipers, headlight doors and heater or A/C controls can all depend on vacuum, and many high-performance engines do not make enough of it. The writer lists variable valve timing, direct injection and turbocharging as common reasons an engine may need a supplemental source.

Camshaft choice is a big factor. The article explains that long-duration, high-overlap cams reduce the vacuum an engine pulls, and that modern EFI engines can idle smoothly on a big cam while making very little vacuum. You may not notice until the brake pedal feels soft.

What the Granatelli Motor Sports Kit Includes

• A rotary vane pump with an enlarged diaphragm, described as quiet and nearly free of vibration
• A Granatelli MAVP (manifold absolute vacuum/pressure) sensor that replaces the usual vacuum switch and relay
• 5 feet of reinforced 3/8-inch vacuum hose, a fused plug-and-play wiring harness and a vibration-isolating bracket
• Four finishes: bare, black, chrome or gunmetal gray, with custom colors available for an extra charge

The article reports that the pump delivers 17 to 23 inches Hg of vacuum with quick recovery.

Installation Notes

In the featured install, the pump was connected to the power brake booster. Wiring is two wires: red to power and black to ground. J.R. Granatelli told the magazine the pump with the supplied hose "is all you need to maintain a firm pedal," and suggested adding a small accumulation tank if one system will also run vents and headlights.

Checking for Vacuum Leaks

The writer also covers leak hunting. Cracked hoses and leaking intake gaskets are the usual suspects, followed by throttle body gaskets and boosters. Symptoms include a rough idle, weak acceleration and a lean air/fuel mixture, and a hissing sound is often the first clue.

Read the Full Article

Read the full installation story at In The Garage Media

More answers are in our Brake Booster Vacuum Pump FAQ, or shop the Granatelli Motor Sports 12V electric vacuum pumps.