How to Install an Electric Vacuum Pump on Your Hot Rod

Granatelli Motorsports’ Solution To The Need for Supplemental Vacuum

By Brian Brennan – Photography By the Author & Granatelli Motor Sports

The car (most likely) parked in your driveway has some form of a factory vacuum pump. It functions via one of two ways: as a mechanical engine driven or electrically powered pump. It generates additional (supplemental) vacuum that is in addition to what the engine can produce. While new cars are designed with these as part of the integral workings, hot rodders need to take the needs this pump provides into consideration. We have a way for you to manage this dilemma: the Granatelli Motor Sports 12V Electric Vacuum Pump Kit.

02 Here are two examples of the Granatelli vacuum pump kit — Here are two examples of the Granatelli vacuum pump kit: gunmetal gray (PN 410103) in an ABS plastic outer shell and the electroplated black (PN 410101).

Why Hot Rods Need Supplemental Vacuum

Whether it be the stocker in your driveway or the hot rod tucked away in your garage, there is every likelihood that a function such as power brakes, wipers, or headlight doors, or some other form of engine management requires ample vacuum to properly operate. Many high-performance engines can be vacuum-deficient; we see this in the hot rod industry often.

03 The gunmetal gray pump is shown with its bracket and wiring ready to go for an installation — The gunmetal gray pump is shown with its bracket and wiring ready to go for an installation.

Common Causes of Low Engine Vacuum

Vacuum pumps are required in engines where the necessary vacuum cannot be garnered through the intake manifold. Think about the following. If your gasoline-powered engine has variable valve timing, direct fuel injection, or a turbocharger, there’s a good chance you will need additional vacuum. A little less exotic, how about power brakes or the controls on your heating and air conditioning system?

What an Electric Vacuum Pump Solves

Oh, did I mention that an auxiliary vacuum pump, such as the Granatelli 12V electrical unit, can add documented 10 to 35 usable horsepower back into the engine? That alone is a great reason.

Granatelli Motorsports 12V Electric Vacuum Pump Overview

04 The Granatelli MAVP sensor eliminates vacuum switch and relay design further eliminating most of the internal wirin — The Granatelli MAVP (manifold absolute vacuum/pressure) sensor eliminates the vacuum switch and relay design, further eliminating most of the internal wiring. Simple two-wire connection … the white wire is not used for this application.

Pump Features, Design, and Performance

J.R. Granatelli, of Granatelli Motor Sports, tells us that his 12V electric vacuum pump uses “forward thinking technology,” which basically means, “The Granatelli design utilizes a rotary vein-style pump with an enlarged diaphragm to ensure maximum suction while remaining nearly dead quiet and vibration free.” It also employs an MAVP (manifold absolute vacuum/pressure) sensor that was designed and patent-pending by Granatelli. It eliminates the need for vacuum switches and relays. The Granatelli pump also guarantees a quick vacuum recovery time, guaranteeing the delivery of 17-23 inches Hg Vacuum.

05 Here is the vacuum canister bracket Granatelli supplies — Here is the vacuum canister bracket Granatelli supplies. It isolates the pump, further enhancing the quiet operation.

Available Configurations and What's Included

The 12V electric vacuum pump kit comes in one of four configurations: the pump alone (bare), which is devoid of an outer shell (PN 410100); a black electroplated shell (PN 410101B); a chrome shell (PN 410102C); or a gunmetal gray (PN 410103) in an ABS plastic outer shell. (For those who wish to add a custom touch, Granatelli also offers custom colors to choose from for an added fee.) Included in the kit is 5 feet of synthetic reinforced 3/8-inch vacuum hose (0.170 wall thickness), an easy-to-install wiring harness (EMI/RFI protected with fuse for “plug-and-play” installation and no additional noise interference), and a vibration-dampening bracket. The pump is fully isolated, maintaining a noticeably quiet operation.

06 Here is the chrome version vacuum pump is bolted to its bracket and ready to go — Here, the chrome pump (PN 410102) is bolted to its bracket and ready to go. The vacuum hose (barb fitting) is loosely positioned but will be pushed fully into the station when installation is complete.

How the Vacuum Pump is Installed

Granatelli also tells us, “The pump, when used with all the supplied hose length, is all you need to maintain a firm peddle. Your brake booster also acts as an accumulation tank, a reservoir of sorts. If your hot rod has no brake booster, the Granatelli Motor Sports Vacuum Pump kit can do the job of both, but it may be a good idea to also add a small accumulation tank if you need one system to run heater vents, headlights, and your brakes.

07 In our installation the vacuum pump is hooked up to the power booster that is an integral part of the power brake system — In our installation, the vacuum pump is hooked up to the power booster, which is an integral part of the power brake system.

How the Camshaft Design Affects Engine Vacuum

For as long as we have seen high-performance street rods with big cams, the subject of engine vacuum is on the table. Does the cam lift affect the vacuum? The result of longer lobe cam durations that are combined with more overlap pulls the air/fuel into the combustion chambers. We have known those qualities in a camshaft that harm the amount of vacuum an engine will pull through its intake plenum.

08 The synthetic reinforced 3 8 inch vacuum hose 0 170 wall thickness is provided with the Granatelli kit — The synthetic reinforced 3/8-inch vacuum hose (0.170 wall thickness) is provided with the Granatelli kit.

The same can be said for LSA engines. For our street rod, an ideal idle vacuum, fuel economy, and tuning all factor into selecting the proper camshaft. These motors that are LSA-equipped (supercharged) make great low-end torque. Furthermore, today’s sophisticated EFI engines can run much larger camshafts, creating far less vacuum while still maintaining perfect street manners. So, you’d never know your baby is idling at say 7 inches of vacuum until you hit the brakes or try to pop open your headlights, only to feel that soggy pedal. The old saying about “everything comes at a cost” also applies here. Idle vacuum suffers with an LSA engine, but something like a Granatelli Motor Sports vacuum pump kit can correct this situation easily.

09 The electrical wiring of the vacuum pump is straight forward — The electrical portion of the hookup is simple. The “black” wire is for ground (-) while the “red” wire is for power (+). In our installation, there was a “white” wire in the wire loom that was not used.

Diagnosing and Fixing Vacuum Leaks

What are some causes of a vacuum leak? Keep this in mind. The most common is the simplest too … a cracked vacuum hose followed by a leaking intake manifold gasket. But it does not stop there. While it is a simple fix, finding a vacuum leak can be time-consuming. Other places to look for a leak are the throttle body gasket, a cracked intake manifold, or a faulty vacuum boost that you might have for power brakes. Should your hot rod have a power booster for the brakes, you may also find yourself with poor brake performance because of the vacuum leak. Oftentimes, a vacuum leak will manifest itself in a drop off in acceleration, reduced power, or a poor idle. This vacuum leak can also cause the air-to-fuel ratio to lean out. Even though your engine may be equipped with a computer, trying to correct this situation, you can still cause severe engine damage. What’s the “low budget” way to find a vacuum leak? Listen carefully—assuming your hot rod has a quiet exhaust—for a hissing sound. If you have spent enough time around motors, you will be able to notice this sound. Keep this in mind.

10 These two illustrations of the inner workings of the Granatelli 12V electric vacuum pump give you an idea how the pump is positioned — These two illustrations of the inner workings of the Granatelli 12V electric vacuum pump give you an idea how the pump is positioned. Also, remember you can get the same pump without the protective housing, if so desired.

Final Thoughts on Installing an Electric Vacuum Pump

Installing the Granatelli Motor Sports 12V Electric Vacuum Pump Kit is a sure way to gain vacuum and cure problems. It will also make your hot rod driving experience much more desirable. Follow along; the installation is a simple Saturday morning project. MR

Sources

Granatelli Motor Sports
(805) 486-6644
granatellimotorsports.com

Hot Rods by Dean
(623) 581-1932
hotrodsbydean.com