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by Phil Ross aka. HoosierBuddy

"Pumps don't suck," Professor Davis liked to tell our Hydraulic Power class. "Or, at least they don't like to" he would sometimes add.

The concept that pumps don't suck might come as big news to anyone with a car like the beauty on Fast Phil's sign; a 1965 Mustang that was equipped from the factory with a mechanical fuel pump. Located several feet away from the car's

Phil Ross is a FordMuscle contributor and goes by the handle "HoosierBuddy" on the FM Forums. He drives a 1965 Mustang Convertible which is in the process of receving a fuel injected 347 stroker.
stock 16 gallon fuel tank, this pump was designed to suck gasoline through a 5/16" fuel line, pressurize that fuel to around 5 pounds per square inch, and pump it into the carburetor's fuel bowls for later delivery to the engine. While a mechanical diaphragm pump is designed to suck gasoline, Professor Davis' point is still somewhat true. Even though they will if they have to, pumps don't like to suck. Pumps work much more efficiently when they have a "pressure head." Fuel pumps are happiest when they are being fed a steady of diet clear, cool pressurized gasoline. This positive feed is one of the major advantages a tank-mounted, or in-tank fuel pump has over an old style engine-mounted pump. If properly designed, these newer style systems use gravity to feed fuel into the inlet side of the pump. A pump that is being fed fuel has a much easier job than a pump that has to suck fuel.

Another major disadvantage of pulling fuel from the tank all the way to the front of the car is that volatile gasoline exposed to the pump's vacuum and heat can tend to vaporize in the fuel line. Vapor lock, the bane of many high performance cars, can easily occur when this happens. A fuel pump that struggles to suck liquid fuel from the tank will fall flat on its face if it suddenly loses prime when low pressure fuel turns from a liquid to a gas while still in the fuel line. This can cause the pump to run dry and wear out in a very short period.

So, what's the horsepower loving street driver to do when the old stock mechanical pump just won't bring it anymore? Turn to a high performance mechanical pump? A pump that will create even more vacuum and heat than a stock pump? For a street driven car in the summer, that fix can be like using gasoline to put out a fire. A high performance mechanical pump may work great on a strip car that gets run hard and shut down quickly, but on the street, that expensive race pump can cause some serious headaches.

A better solution is to ditch the stock mechanical fuel pump mounted on engine's front cover, and go with a pump mounted closer to the gas tank. Your grandfather might have seen a few vacuum driven pumps before the war, but in this day-and-age a pump mounted away from the engine is generally powered by electricity. A good electric fuel pump, properly sized, selected, and installed can be a great improvement for your hot rod or vintage muscle car.

Keep in mind though that electric fuel pumps are not all the same. Pumps are rated to operate at different pressures and different flow rates. Also, while many electric fuel pumps are designed to be mounted between the gas tank and the engine, some are designed to be mounted inside the tank itself. While mixing the electricity that it takes to run the pump with gasoline might seem a bit disingenuous at first, in fact that is the system that is preferred in many OEM applications like all late model mustangs. Newer mustangs and many other late model cars have their fuel pumps mounted in the gas tank.

In-Tank Fuel Pump Considerations
When considering a retrofit installation, mounting the pump in the gas tank is a little more involved than mounting it outside the tank. Mounting the pump in the tank has a few definite advantages though. Most importantly, the fuel tank inlet can be located very close to the lowest point on the inside of the tank with relative ease. Secondly, the pump itself is submerged in gasoline that will keep it nice and cool when it's in operation. Third, a pump that's inside the gas tank tends to be quieter than a pump mounted in the open in front of the gas tank. Finally, locating the pump in the tank eliminates the hassle of trying to find the perfect compromise location for an externally mounted pump. External pumps work better the lower they are mounted. However, get them too low and they might get hit by something off the road. Once you've decided to mount the pump in the tank, you have all the room in the world, or at least all the room in the tank, to mount it in.

While mounting a pump in a late-model mustang gas tank that was designed for that specific purpose is a fairly simple job, mounting a pump in an older tank that has no provision for an internal pump has involved a lot of engineering, custom design and fabrication for those hardy souls that have pioneered in-tank fuel pump mounting for older cars. Luckily, as more and more hot rods and muscle cars have been converted to Electronic Fuel Injection, that by its nature requires higher fuel pressure, necessitating electric fuel pumps, the aftermarket has responded. Tanks Incorporated manufacturers and sells complete "universal" in-tank fuel pump assemblies that can serve as the basis for an in-tank electric fuel pump system. The Tanks Inc. unit is a well thought out assembly that already has the engineering and design work built right in. This is good news for those of us that are ready to upgrade our fuel systems for the new millennium.

 

Installation
Although it is possible to assemble the PA-4 kit into an existing gas tank, this does create a large safety concern. It is extremely difficult to empty a gas tank completely, remove every bit of gasoline residue, and vent all the flammable vapors left by gasoline. Never cut, drill, bore, weld or file on a gas tank that has the slightest trace of gasoline in it. The safest and best thing to do is to purchase a new fuel tank for this sort of conversion.



For our installation on a 1965 Mustang Convertible, we elected to ditch the old, original style 16-gallon tank and install a 20 gallon tank that was designed for a 1969 Mustang. This tank is the same width and length as the stock unit, but is slightly taller above the flange to allow for the additional capacity.
 
The unit shown is an American Designers tank manufactured north of the border by our friends in Canada. It includes a very handy drain plug too. Be aware the sending unit, which powers the car's fuel gauge, must be matched to the gas tank. So in this case, we needed to purchase a new sending unit for a 1969 mustang as well. It will work fine with the stock gas gauge.
     

The pump assembly should be mounted toward the front and near one side of the tank to maximize the benefit of the anti-slosh baffling. Here, the 6" diameter mounting ring is used as a template to draw an outline of the hole that must be made in the tank. A jigsaw could be used to make this cut, but if available, a hole saw will make short work of this job.
 
Since we planned to use a hole saw, the next step was locating the exact center for the pilot hole. If you remember anything from high school geometry, you might remember this: 2 chords struck across the intersections of two radii scribed from the circumference of a circle will cross at the circle's exact center.
     

HUH??? Well…have your smart teenager show you how to find the center of a circle or make your best guess and start drilling. Either way, you'll end up with a hole.
 
After center punching the exact center for our circle, we proceeded to void the warrantee on our new American Designer's 20-gallon tank. A 4 ½" hole saw is the slick way to make this cut. Unfortunately, a lot of hardware stores don't carry hole saws bigger than 4" and the ones that do charge about 35 bucks for one. Luckily, a friend of a friend was found that had this saw in their tool box and made it available. Aren't friends with tools great to have around?
     

(Installation continued)
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In This Article...
Learn the benefits of installing a late-model style in-tank fuel pump in your classic Ford muscle car.


 
Tanks Inc. Conversion Kit
Here we see all the goodies that come with the Tanks Inc. PA-4 Fuel Pump package. The kit includes a baffled assembly to protect against fuel slosh, inlet and return tubes, fittings, mounting hardware, a gasket, and a Walbro fuel pump rated at 250 liters per hour.


Fuel pumps need to be sized properly for the engine they will feed. In our case, we will be using the new pump to eventually supply a 347 stroker with EFI. The 250lph pump will support about 400 normally aspirated horsepower, EFI or carbureted as long as the proper fuel pressure regulator is utilized. Initially we are installing a return style fuel pressure regulator adjustable to around 5 pounds per square inch to the current carbureted 289 motor. We'll switch over to an EFI regulator once the 347 is in place.

 






 


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