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.
Whether it be the stocker in your driveway or the hot rod tucked away in your garage, there is every likelihood 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.
Does your hot rod have a remote vacuum pump, or should it have one?
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 have need for additional vacuum. A little less exotic, how about power brakes or the controls on your heating and air conditioning system? 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.
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.
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 410101); chrome shell (PN 410102); or 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.
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.
Read More: EFI Troubleshooting/Tuning Tips
For as long as we have seen high-performance street rods with big cams, the subject of engine vacuum is on the table. Does cam lift affect vacuum? The result of longer lobe cam durations that are combined with more overlap pull the air/fuel into the combustion chambers. We have known those qualities in a camshaft harm the amount of vacuum an engine will pull through its intake plenum.
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.
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 is 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.
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
Granatelli Motor Sports
Hot Rods by Dean