If you own a classic car and you want to keep things 100% original – right down to the carburetor – you probably wouldn’t think about installing a custom fuel tank. But once you start modifying things, such as converting to an EFI system, then a custom fuel tank starts moving up on your list of priorities.
A typical fuel tank on a classic car is just a large, unchambered reservoir and the harder you drive the car the more the fuel moves inside the tank. Make a hard right turn, and inertia causes the fuel to move left. Accelerate hard, and as the car lunges forward inertia causes the fuel to move backwards.
We learned this simple principle in physics class: it’s called Newton’s First Law of motion, or the law of inertia. In simpler terms, and for this article, we call this form of inertia fuel slosh.
To solve our fuel slosh problems, we reached out to Hector and Rick Guerrero, father and son owners at Rick’s Tanks, to help explain how to properly control fuel slosh inside a fuel tank, and to provide us with a solution to our fuel starvation woes.
Controlling fuel slosh inside the tank might not be as important with a carburetor because some fuel is stored in the carburetor’s fuel bowl. The bowl typically stores enough fuel that inertia inside the tank doesn’t become much of a problem for regular driving. But fuel slosh can be a big problem with fuel injection conversions because the only stored fuel is in the tank itself.
After Project Track Attack was converted to EFI, we began to battle with fuel slosh during competitive events. We tried a couple of methods to control fuel delivery, but throwing the big B-body around in the turns proved to be too much for the factory fuel tank.
We even purchased an aftermarket tank, but that didn’t solve our problems and we were baffled as to why we still had fuel starvation issues. Rather than trying to fix what we knew was already broken, we decided to go to the experts for some answers.
Baffled Fuel Tank
With our first baffled fuel tank purchased from a local hot rod shop we had hit the track again, but after a couple of hard turns we still found that fuel starvation was affecting our lap times, as well as our speed in the corners. In other words, the baffling wasn’t doing its job properly.
The tank we bought looked great, but what was on the inside mattered much more than how it looked on the outside. We needed to find out why we still had these issues, so we removed our fuel tank and sent it to Rick’s Tanks for their opinion, and an explanation as to why our baffled fuel tank was leaving us…well, baffled.
Owner Hector Guerrero cut the top off of our tank to have a better look inside, and to help us determine where the problem was. “They did a good job on the tank, it’s a nice unit,” he told us, “but the area for the fuel pump is still a little too big to control fuel slosh.”
The problem wasn’t that the tank didn’t have baffles, it was that the baffles were not in the proper location. One of the bigger problems was that the fuel pump had been mounted at the front corner of the tank. The car did okay on left turns, but right turns pulled the fuel inside the baffled area away from the pump, and that is when fuel starvation happened.
Controlling Fuel Slosh
There are a couple of ways to deal with fuel slosh for vehicles converted to EFI, and how the car is going to be used is a key factor. For many people who drag race, a fuel cell is a great way to control fuel slosh, but for a regular driver giving up valuable trunk space and fuel volume becomes an issue.
Most fuel cells are a bit smaller because they’re made for racing applications and they only hold about 10 gallons of fuel. Our car doesn’t hit the 1320, but it does see a lot of street use as well as hitting a racetrack a few times each year, so we needed something that would allow us to drive a little further than ten gallons of gas would allow.
To control fuel slosh a baffled tank is necessary, and based on whether the driving style is drag racing or road racing will help determine where and how the baffles need to be installed. But simply putting baffles into a tank won’t cut it, they serve a purpose and need to be designed to keep the fuel in a certain area in the tank, namely, the lowest part of the tank.
Baffles inside the fuel tank help keep the pickup point for the fuel pump submerged in fuel so that the fuel pump is constantly pumping fuel to the engine. If the fuel is pulled away from the pickup during acceleration or hard cornering, the pump begins to pull in air, and for an EFI system that can mean loss of power – or complete shut down – because EFI requires consistent fuel pressure.
Guerrero said, “Our main goal is to keep as much fuel as possible in the lowest part of the tank, and to put the pump where there will be the least amount of fuel slosh.”
As you can imagine, fuel tanks come in thousands of different shapes and sizes, but Rick’s can make a direct replacement that will fit the vehicle properly, and has internal baffles to keep the fuel where it needs to be.
As we mentioned, one of the biggest problems with our first tank was that the baffling was in the wrong place, and that caused a few other issues. The rear baffle was too far back and that caused some issues with filling the tank, as well as allowing the fuel too much movement during hard acceleration. As a result fuel often splashed up the filler tube and past the fuel cap.
Guerrero said, “If the rear baffle is not in the right place, it won’t control fuel slosh, there’s a balance to putting baffles in the tank. You can really bias a drag car tank. The first 60 feet needs help with fuel control.”
“We create a bias so that the fuel gets to the pump and reduce the capacity to increase the fuel flow,” he said. These reduced areas are populated by the fuel pump and are kept small so that the fuel cannot move much during hard acceleration. The principle is similar with road racing fuel tanks, however, they not only need the fuel to stay near the pump during acceleration, but during cornering as well.
Building a Stainless Steel Fuel Tank
All of the tanks that Rick’s Tanks builds are made from 16 gauge 304 stainless steel. A pattern is made on the sheet and it’s cut with a power sheer or a plasma cutter to begin the new tank. A press brake is used to make bends, and after all shapes are cut the pieces are TIG welded together to form the tank.
Guerrero recommends that when ordering a fuel tank to let them know if any custom work has been done to the exhaust or rear suspension. Other things that go into the design of the tank is the horsepower of the car, how it’s driven, whether it’s naturally aspirated or forced induction, and the exhaust diameter.
They’ll also need to know the ohm reading for the fuel gauge so they can install the proper sending unit for the vehicle. The tanks will come with a pump and a sending unit unless otherwise requested.
We already had a new Aeromotive Stealth 304 fuel pump installed, and they already have the templates for the fuel pump flange for most pumps on the market. Since we had a popular pump it wasn’t a problem and we didn’t need to send them our pump.
“Our first challenge is the shape of the tank,” Guerrero said, “We want to reproduce the shape of the factory fuel tank. The second challenge is where to put the baffles.”
Our first challenge is the shape of the tank. The second challenge is where to put the baffles. – Hector Guerrero
Looking at the internals of the tank, the cavity that encloses the fuel pump is much smaller than it was on our previous tank. That area holds enough fuel to keep the engine running and has small notches at the bottom that allow fuel to enter the cavity, but won’t let it escape very quickly during spirited driving.
Whenever we filled up with fuel, a splash of gasoline would come from the filler pipe just before the automatic shut off occurred with the nozzle. Having the baffle so far back didn’t do much for controlling fuel slosh, it only made it a problem when filling up. Even as we drove the car, any fuel that was in the rear part of the tank ended up splashing out of the filler.
Our real problem with the prior tank came about during regular driving when we noticed that at a half-tank of fuel we still had fuel starvation on freeway ramps, for racing we even had those issues at three-quarters full. The area in the center of the tank was too large of a cavity and it didn’t help to equalize the fuel in the rest of the tank in the smaller baffled areas.
Guerrero takes all of this into consideration that most of the fuel is kept in the lowest part of the tank, but the baffling needs to slow the movement of fuel from one section to another. The way the fuel is controlled is with small areas where the fuel can flow from one section of the tank to another, but not flow through that area too quickly.
Installing The Tank And Filling Up
With the fuel pump and sender installed, we connected our hoses to the tank and put some fuel in the tank to make sure we don’t have any leaks out of the top. Tilting the tank forward so that the fuel reaches the fuel hat will let us know if we have a leak at the gasket or not, and once we were satisfied with the seal we proceeded to install the tank. Filling up with 15-20 gallons with the tank installed is not the time you want to find out that a gasket isn’t sealing properly.
Installing an empty fuel tank might seem like an easy task, but keeping it level and centered is important. We also needed to connect our fuel lines to the Aeromotive Phantom pump that we installed, so we needed to raise the tank and connect the lines while we still had access to the fuel hat. To help hold the fuel tank in place, and to insulate it from the trunk floor, we used a 3/16-inch rubber sheet between the tank and the underside of the car. It was purchased at an industrial supply store in the area and was cut to size for us.
In order to do this installation ourselves, we built a jig for the floor jack from spare lumber in the garage to hold the tank level, and raised the tank enough to connect the fuel and electrical lines. Our tank had a single strap in the middle, which is another reason why using a floor jack alone would have been a problem. The jig we built allowed us to install the tank strap that Rick’s Tanks supplied.
Before we completely installed the tank, we inserted the filler tube into the filler grommet in the tank, and made sure it was centered and secure, then we raised the tank up to the trunk floor and tightened down on the tank strap. The tank needs to be secure and the strap needs to be tight but care should be taken to not overtighten the strap. Guerrero tells us that we won’t have to worry about compressing the tank, but we could damage the strap.
Upon first filling up the tank it takes a few minutes for the fuel to reach the baffled area. This is because each baffled area is designed to keep the fuel from flowing too quickly from one baffled area to another. Once the main area is filled, that’s where most of the fuel ends up staying. Unlike some tanks, ours is long, and has a low spot towards the front. Inside, a baffle will keep that fuel from splashing back to the filler like it did on the prior tank.
Ready For The Track
Our first test with the car was to fill up the tank about half way, and take it out to one of the freeway ramp cloverleafs and see if the fuel slosh problem went away. After a few attempts, we noticed no fuel starvation issues and we knew we were ready for the track. Willow Springs was calling again, and in early October we hit the big track and ran the car hard.
Filling up prior to racing wasn’t a problem this time, because the baffling was in the proper spot and we didn’t get black flagged for spilling fuel out of the filler. After a day of racing, and seeing the fuel level get down to a quarter tank, we continued to push the car hard in the turns and the new tank performed as expected. Even with the lower fuel level, we experienced no fuel starvation problems out on the track.
There are plenty of shops that will build a fuel tank for you, but its important to know that they have experience in building a tank and baffling it properly. It’s not an inexpensive purchase, and if you don’t do your homework you can end up with something that doesn’t perform properly.
This is not to say that the prior tank was not built well – it was a nice tank. But for the type of driving that Project Track Attack sees occasionally, we needed to make sure that the tank was built by a reputable shop that specializes in building fuel tanks.
After a month of driving the car and two days of racing, we are pleased with our selection of Rick’s Tanks to keep the fuel where it needs to be. We went as far as sending our original fuel tank and our fabricated tank to Rick’s Tanks so they had one to match up, and also to inspect our aftermarket tank to see where the problem was. This isn’t always necessary, but if they don’t have a pattern for your car, sending the tank will help them replicate the shape and dimensions.
Rick’s has hundreds of patterns for fuel tanks for some of the more popular musclecars, but they can also build a custom tank for just about anything. You can get in touch with them through their website, and keep tabs on what they’re up to on their Facebook page. And once you’re baffled, it’s time to hit the track with confidence.