How to Add an EFI Fuel System to Your Muscle Car

10 min read

How to Add an EFI Fuel System to Your Muscle Car

10 min read
Holley EFI fuel system options.

Adding EFI to your ride has never been easier. Now, adding a fuel system to match is, too.

Back in the day, converting a carbureted vehicle over to electronic fuel injection was fraught with potential peril. From complicated wiring and tuning issues to concerns about parts compatibility and flow rates, it was a bit of a daunting prospect for shade tree mechanics and veteran gear heads alike. A lot has changed in recent years, though.

“It’s become far more accessible to the average guy,” says Holley project engineer Matthew Sosa. “These systems are much more of a plug-and-play kind of deal these days, and you don’t need to have a ton of EFI tuning knowledge to get it to run the way it’s supposed to. It’s a lot simpler than it used to be – we’re talking six wires with a Sniper system. And for those who want to get into the more advanced tuning stuff, that’s still there as well.”

Whether you want to go mild or wild, these days there’s a wide range of different kits available to get an EFI system up and running on just about any muscle car. But as with any project, an array of choices can lead to some uncertainty in terms of determining the best approach. Here we’re going to take a look at the various options builders have to get their fuel systems ready for EFI, and get the low-down on which types of applications each setup makes the most sense for.

Learn more about Drop-in Fuel Sender/Pump Modules

If you’ve got a street machine making up to 550 naturally-aspirated horsepower and you’re looking to get your fuel system EFI-ready, this will likely be the simplest, most straight-forward way to do it.

“We did a market analysis and made sure from the outset that we hit the big ones,” Sosa says. “We’ve got at least 19 different kits here, and each was developed for a specific platform, like ‘55 to ’57 Chevies, second generation Camaros, 1968-70 Mopar B-bodies, 1964-70 Mustangs, and so on.”

Muscle Car EFI Fuel Tank Modules are an extremely easy and cost-efficient way to add an in-tank pump. They install into your factory tank (application specific) in place of the fuel sender and feature a new sender, high-pressure pump, integrated fuel pressure regulator, and Holley HydraMat, a patent-pending fuel reservoir system that reduces fuel starvation issues.

Geared toward throttle body or multi-point-style EFI systems, these drop-in kits were developed with hassle-free simplicity in mind. “These units are designed to go into your factory fuel tank and they work with your factory hard line as well as your factory gauges,” Sosa explains. “So you don’t have to buy all-new lines and fittings and route them – it simplifies things a lot from an installation standpoint, and you won’t have to spend more money on a bunch of other stuff along the way.”

Both the pump and regulator are built into the unit, and since it’s a returnless system, you don’t have to worry about running a return line, either. “For the most part, factory-carbureted fuel systems are returnless, so you’ve already got the feed line you need,” Sosa adds. “You can add a return line if you want to, but you definitely don’t have to.”

Factory-style EFI Conversion Fuel Tanks

If you’re in the middle of a restoration project, or you’ve noticed your fuel system could use some attention in general, this solution might be just what you’re looking for.

“A lot of these cars are forty, fifty, sixty years old or more now,” Sosa points out. “And the same goes for the factory fuel tank if it hasn’t already been replaced. In some cases that’s fine, but in others you might discover that there’s a bunch of rust and other junk in it, and that stuff is going to make its way into the fuel system if it’s not addressed.”

One option is to buy a factory reproduction tank and use the aforementioned drop-in module system we detailed above. But if you want to skip some of the guesswork and get an all-in-one solution, Holley’s factory-style EFI conversion fuel tanks are the ticket.

“It’s all done for you – these tanks already have the pump, level sensor, tank and everything else ready to go in one package,” Sosa notes. “You’ve got everything you need right there, and you know ahead of time it’s all going to work together.”

As with the drop-in modules, these packages are rated for up to 550 naturally aspirated horsepower as-standard, but builders with forced induction applications and/or those making more than 550hp do have some options here as well.

“Most of these packages are available with a 400 liter/hr pump module, rather than the standard 255 liter/hr pump, and we also sell that 400 liter pump separately,” he adds. “That will support up to 750 horsepower, so it’s great if you’re really pushing those power levels, and it’ll provide more flexibility in terms of boost levels for the guys running forced induction.”

In-tank Retrofit Fuel Modules

If you’ve got a project that’s a bit unusual and the two options mentioned above don’t apply, this retrofit approach is for you. Designed to be installed on a tank that doesn’t have an application-specific drop-in module, a builder going this route would install this by cutting a hole in the top of their existing tank and installing the module inside.

“The system has these swing-out clamps that lock the module securely to the inside of tank,” Sosa says. “And we have versions that are returnless – the same kind of system as the drop-in units – as well as return-style systems for people who want to run an external regulator.”

While in-line external pumps are an option here as well, there are some benefits to installing the module inside the tank that are particularly notable for folks doing EFI conversions on street cars.

“There’s a reason why the OEMs do it this way,” he tells us. “First off, you’re keeping the pump cooler – the fuel itself actually cools the pump, so that will benefit the pump’s potential longevity. The other benefit is noise reduction – external inline pumps are not quiet, and they tend to use the chassis as a tuning fork when they’re on. When you suspend the pump in fuel, the noise is dampened by that fuel, and it’s also suppressed by the tank itself as well as its physical distance from the passenger compartment. That might not be a big deal if you’ve got a really rowdy car to begin with, but others might not want to hear that high pitched hum.”

Pumps ranging from 255, 340, 450, and 525 liters/hr are available with this solution, with the latter supporting up to 1200 EFI-fed horsepower.

external efi pump

External pumps, such as this, Atomic EFI pump (2925) are extremely easy to install and very economical but tend to run hotter and louder than in-tank pumps due to the lack of liquid insulation.

External In-line Pumps

If you’ve got a dedicated race car, an external in-line pump offers a few important advantages over an in-tank solution. “A lot of drag racers and road race guys use these because it is super easy to service or change out the pump in this setup – you don’t have to pull the tank down or take a fuel cell out,” Sosa says. “And some guys like them for street applications for the same reason.”

And while this setup doesn’t have the same cooling benefits as an in-tank module, Holley has designed these in-line pumps to function similarly. “Basically the pump is encased in a fully sealed housing, and that housing is allowed to fill with fuel as it flows through from the low pressure side in order to provide that same cooling effect for the pump and enhance its longevity.”

Some of Holley’s in-line systems are also available with dual pumps, which can be set up as either supplemental or redundant setups.

“Let’s say you have a boosted application,” Sosa posits. “Cruising around, you only need to run on one fuel pump. But when you get into boost, you need the volume of that secondary pump, and you can set it up in our EFI software so that the second one will automatically come on when you need it.”

And in racing applications, redundancy ensures that if there’s a problem with the primary pump, you’re not faced with a potential DNF. “If you’re in the middle of the race and there’s an issue with the primary pump, you can literally flip a switch and move to the secondary pump. That can be a game changer in endurance events, and that’s one of the reasons why you’ll find these pumps in a number of different racing series.”

Brushless Pumps

Whether it’s a seriously potent racing machine or a particularly brutal street car, those with extreme applications should check out Holley’s new brushless pumps.

“We’re talking about ludicrous power levels here – each of these pumps will support up to 2200 horsepower from an EFI system,” says Sosa. “So with the dual-pump housing options, you’re potentially looking at north of 4000 horsepower.”

The VR2 brushless pump is an extreme duty pump designed for engines making huge power. The VR1 supports 2,200 horsepower where the VR2 (two pumps in one housing) can support 4,400! Brushless pumps use a controller that allows precise metering of pump output.

Along with their massive flow capacity, a key benefit of the brushless pumps is their low amp draw, which is especially helpful for race teams. “A lot of the cars at these power levels aren’t running alternators for a number of different reasons,” Sosa notes. “So a lot of these race cars are running sheerly on battery power, and some of those bigger traditional pumps can pull a lot of energy. These brushless pumps are far more efficient – the VR2, which is two pumps in one housing with the capability of supporting 4400hp, has a maximum draw of 38 amps. If you used four brush pumps to get similar capacity, you’d be looking at more like 80 amps.”

Holley Fuel Cell Module

Holley Fuel Cell EFI Pump Module Assemblies are designed to attach to popular 12-bolt fuel cell caps, making them very quick to install. They have convenient AN style ports and can support up to 1,100 carbureted horsepower.

Brushless pumps are also designed to work with a dedicated brushless controller, and that allows for significant flexibility in terms of pump capacity. “You can run one pump at half speed, one at full speed, both at half speed, or both full speed. So with one pump running at half speed, this would work fine in an EFI setup running around 1100 horsepower, which is about the same output as a single 525 liter/hr brush pump. You have a wide breath of flow ranges you can use here, and you can stage them in as necessary.”

And that means that if you have a Holley EFI system, you can have it interface with those brushless controllers to tell it to change based on variables like boost levels and throttle position. So, if you wanted to, you could still run one of these on the street.

EFI Fuel Cell Pumps

Also aimed primarily at the motorsports set are the EFI fuel cell pumps offered by both Holley and Sniper. “These are also available in single and dual pump units, and they’re designed to mount directly to the fuel cell filler, so you get those benefits of an in-tank system,” Sosa explains.

Offered the standard six, ten, twelve, and 24-bolt patterns (the latter as an adapter for the twelve-bolt option), these pumps have an integrated fill cap and AN-style inlet and outlet fittings so you can adapt this system directly to your existing fuel cell setup with zero hassle.

“It a nice, clean package, and you get that additional cooling from the in-tank design versus an in-line setup.”

Adding EFI to your muscle car, whether a fire-breathing race machine, or a vintage cruiser, is a task that can be accomplished in many ways. That said, it's far from insurmountable, and with the amount of universal options available to make it pain-free, one should ask themselves what's keeping them from the added drivability, fuel, economy, and power electronic fuel injection has to offer.


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