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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?
     

 

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.

 






 

 

"Hey Pierre! This new tank you made me seems to have a hole in it."
 
At every step of this project, any burrs that are created need to be cleaned up. The last thing you want are small bits of metal breaking off at some later date and ending up in the fuel system. Here, we are using a half round file to clean up sawn edges of the sheet metal tank.
     

The next step in mounting the Tanks Inc. kit is to flatten out the sheet metal around the 4 ½" hole to give a flat surface for the pump assembly to seal against. The flat area needs to be about ¾" wide. This step requires some patience and an assortment of tools. A pair of vise grips can be used to pinch the tank's ribs flat.
 
If you have a wide welding clamp around, you can use it to flatten out the ribs in a more even manner than is possible using the thinner vise grips.
     

When all else fails, go for the big-fricken-hammer. Here, we're using a 2-pound engineer's hammer as a dolly inside the tank and applying a beating with a ball peen hammer around the 4 ½" hole's circumference. With some care, this method can be used to even out a circular area around the hole.
 
Once the area around the hole is relatively flat, the kit's support plate can be clamped in place and used as a template to locate the bolt holes that must be drilled. While it would be possible to carefully mark the holes, remove the plate, center punch the marks and then drill the holes, this method might introduce some errors in hole placement. That would create problems. So, we decided to clamp the plate in place and use a sharp 1/8" drill bit to locate our holes. Care was taken to insure the bit did not rub against the edges of the bolt holes in the plate. These holes are threaded, and the flutes of the drill could cause damage if care is not taken.
     

Here are the holes drilled out to the proper size. You'll note that the area around the mounting holes is as flat as we could make it using available hand tools.
 
A shop vac is useful to get some of the metal shavings and debris out of the tank. However, this alone is not sufficient. All of the steel burrs, shards, chips and dust must be cleaned out of the tank. A tack cloth is an excellent tool to wipe down the inside of the tank and pick up metal dust. A magnet is also a good tool. Plan on spending a good thirty-minutes cleaning out the tank.
     

Here's a handy tool, a 14-year old with steady hands and a fine attitude. (The metal cutting band saw is a handy tool too of course, and won't cause your automobile insurance to skyrocket when it turns 16. )
 
We've marked the fuel pump support to give us 8" of overall height to our fuel pump assembly. When mounted, this will put the bottom of the anti-slosh tray right against the high points of the bottom of the fuel tank. The Tanks Inc. fuel pump assembly has several mounting slots that can be used in to mount the anti slosh tray. However, in our case, none of the mounting slots were able to be used, as the 8" assembled height is somewhat shorter than was originally envisioned for this pump assembly.
     

A mounting hole is needed in the support bar to fasten the anti-slosh tray to. The hole is carefully marked
 
The mounting hole is then drilled as indicated.
     

The tank is set into place to check the position of the inlet and outlet fittings with the pump assembly rotated to the correct position.

Next, it's time to give some thought to how the pump assembly will need to be rotated in the tank to get maximum benefit from the anti-slosh baffling. Tanks Inc. recommends mounting the pump toward the front of the car, near one side of the tank or the other, with the anti-slosh tray running side to side. The anti-slosh tray includes an auxiliary fill hole that should be pointed toward the nearest tank wall. In our case, it should have pointed toward the driver's side of the tank. However, due to the radius on the bottom of the tank, our mounting location required the anti-slosh tray to point toward the center of the tank rather than the side. This put the auxiliary fill hole facing the wrong way. If left uncorrected, this would allow fuel to move away from the pump during left-hand cornering, so a fix was needed.
 
A bolt and nut were used to plug the auxiliary fill hole. New holes were drilled on the other end of the tray. The purpose of these holes is to allow the anti-slosh tray to pick up fuel during situations where the tank is nearing empty. When the car accelerates hard or turns right, the remaining fuel will tend to slosh to the driver's side tank wall, form a swell, and fill the anti-slosh tray through the auxiliary fill holes. Of course, like all fuel pumps, this Walbro pump should never be run dry, so the best solution would be to keep a few gallons of fuel in the tank to help the anti-slosh baffling keep the pump inlet covered with gasoline at all times.
     

Here's the other side of the tank assembly. The pump is clamped in place with the filter just slightly above the tray bottom. The fuel return line is cut off about an inch above the tray bottom. You'll note that any fuel that is returned to the tank by the return style fuel regulator will help to refill the anti slosh tray. A constant flow of high pressure fuel to the engine and back to the tank's return line should make vapor lock a distant memory for our vintage ford.
 
How do you get a 6" ring into a 4 ½" hole? The designers at Tanks Inc. have that puzzle solved. The mounting ring is split so it can be maneuvered inside the tank as shown.
     

A few of the included mounting screws can be used to locate the support plate inside the tank and hold it in the proper position.
 
While not completely necessary, it is a good idea to tack weld the edge of the support ring to the top of the tank. This will prevent the ring from being dropped into the tank if the pump assembly must be removed in the future. The kit includes fasteners that will allow the pump to be assembled with no welding whatsoever. However, welding the ring in place makes a lot of sense if you're using a new tank and have a suitable welder available.

Four or five small tack welds are sufficient to permanently mount the support ring. Any weld bead that sticks upward above the original gas tank surface will cause sealing problems so they should be carefully ground flush before going any further. Also, after all of this welding and grinding don't forget to use your tack cloth to clean the inside of the tank out again. Remember, metal dust and moving parts do not a happy couple make.
     

A good aircraft quality gasket dressing should be applied to each side of the cork gasket included with the PA-4 kit. This will help insure a tight seal around the new pump assembly. The gasket dressing should be allowed to dry for a few minutes before final installation.
 
The bolt threads are a potential leak source too. Tanks Inc. recommends anti-seize on these threads to help seal them. Obviously it will help in disassembly too, should the pump need to be replaced in the future.
     

The pump assembly can now be set into the tank using the gasket we prepped in step 23, and "clocking" it to our predetermined position.

 
The final step in mounting the pump to the tank is simply starting all of the included bolts through the top plate and gasket and screwing them into the support plate mounted inside the tank. Do not over tighten the mounting bolts. They should all be tightened evenly and firmly but care must be taken to prevent any crushing of the cork gasket. If the gasket is crushed a fuel leak is likely. Here, we're using a nut driver to start all of the mounting bolts. An end wrench or socket set should be used to snug the bolts to their final torque.
     

Now that the pump is assembled and mounted in the tank, we are ready to run a new larger fuel line as well as a brand new return line in our vintage mustang. A high pressure fuel filter, pressure regulator, and proper tank venting must also be included for the system to work properly. These items, including how to properly wire the fuel pump, fuel pump relay, and an inertia switch, will be covered in a future article as the final step in upgrading a vintage Ford's fuel system for the new millennium.


Posted by strtcar, 02/23/08 03:32pm:
bravo...bravo..night write-up
Posted by eliteman76, 02/24/08 03:06pm:
Good article. I think this would be of benit fit to guys like me running the 72-up intermediates, but at the same point, what is the cost for this kit, the tank, versus going to a safety fuel cell with pump? I would be inclined to go this route, but at the same point for the money would rather put a steel case fuel cell in. What about running a return line? What sort of rating does there line support?
Posted by Husky44, 02/29/08 11:44pm:
Great Aticle, but I couldn't find a link to purchase the system. Am I just web-challenged?
Posted by Starhonk, 03/01/08 02:07pm:
Go to the company's website and call them. http://www.tanksinc.com/





 

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