Electrification might be the latest trend that’s on enthusiasts’ minds these days, but let’s not forget that we’re currently enjoying the second golden age of the muscle car. Factory-produced hot rods with supercharged V8s that dish out nearly 800 horsepower are readily available at dealerships all over the country, and many more late model muscle cars that are currently on the road are just a few bolt-ons away from those power levels – or even more.

Getting big horsepower is more than just a matter of throwing a turbo or a blower into the mix and calling it a day, though. If you want power that’s consistent and reliable, you’re also going to need a fuel system that’s up to the task. And that’s where Holley’s range of drop-in fuel pumps come into play.

“Over the past few years, we’ve been hard at work developing fuel pumps for late model muscle cars that would enable these vehicles to support significantly more power than the factory pump can handle,” says Matthew Sosa of Holley Performance.

“If you’re going from a naturally aspirated setup to forced induction, or are looking to move over to E85 to make big power, the reality is that the stock stuff probably isn’t going to cut it. So we started with the 2011-17 Ford Mustang and its Coyote 5.0-liter V8, and then we introduced support for the Hemi-powered late model Mopar passenger cars – Dodge Challenger, Charger and Magnum, along with the Chrysler 300. And now we’re working on some of the GM stuff as well.”

Properly Feed The Beast

Sosa explains that the design limitations of modern OEM fueling systems can pose a challenge for builders that are looking to take things to the next level.

“Most modern fuel tanks straddle the driveshaft – hence the name ‘saddle tanks.’ They basically have two main cavities and a crossover in the middle. The issue is that with the factory setup you’ve got a pump on one side of the tank, so they needed to figure out how they were going to transfer fluid from the side of the tank that doesn’t house the pump to the one that does. To do that, the factory systems use a venturi jet pump and use a portion of the fuel pump’s output to drive this jet pump to create a vacuum that pulls the fluid over from the other side. And that jet pump system uses up to 20 gallons per hour of fuel pump’s output. That’s flow being used just to make that transfer from one side of the tank to the other happen.”

Factory systems are typically oversized to account for that additional burden, but it also means that when you’re adding significant amounts of power to the vehicle, the fuel pump can quickly run out of the headroom required to accommodate it.

A few years ago, the engineers at Holley noticed that while many other solutions on the market put multiple pumps on the same side of the tank, they didn’t incorporate a venturi jet pump into their design, and that resulted in significant caveats for the end-user. “They’d made these stipulations that you basically couldn’t run their pumps at lower than half a tank of fuel,” Sosa says.

“And reason for that is because half a tank in a modern car equates to one side of the tank being almost completely full while the other is pretty much empty. So you’ve effectively cut your fuel capacity in half because there’s no transfer happening from one side of the tank to the other, aside from slosh, and the pumps are only pulling from one side. We didn’t think that was a very good solution.”

Holley instead developed a system for those initial applications that placed a pump on each side of the tank to allow the system to draw from its full capacity. “We also put HydraMat on the modules to ensure that they would handle low levels of fuel well, too – even with the higher flow rates,” he notes.

Elements of the factory fuel pumps’ designs were incorporated into these new modules for the sake of packaging and overall ease of use, but with a few key differences. “We eliminated the jet pump from the equation because, at 20 gallons per hour, that’s costing you roughly 200 horsepower of support on gasoline. And to address that fluid transfer issue, we incorporated a section of submersible fuel line that can be used as an internal crossover. That way you still only have one outlet, but the secondary module is able to feed the primary module through that crossover line.”

Don't think we've forgotten about older platforms, either! Drop-in modules for older cars, like the ones pictured (from left to right: 1974-1981 GM F-body, 1963-1976 Mopar A-body, and 1978-1988 GM G-body) are designed to drop in, replacing the stock fuel sending unit. They support fuel injected applications with pumps rated from 255 to 525 LPH pumps.

The modules include 3/8ths and 5/16ths Quick-Connect fittings, too. “The factory fuel line will support a more power than a lot of folks think they will,” Sosa points out. “So we tried to limit the amount of plumbing that would be required to make this work. But the modules also have -8 O-ring ports in the flanges for both the feed and return, so you can run AN plumbing if you want to.”

They’ve also been designed so that users can configure the system to be return or return-less. “We put 4.0 bar regulators into the flanges,” he says. “Obviously that will work great for a naturally aspirated setups, and it’ll work well with mild boost – maybe running a supercharger with 10 to 12 psi of boost. Or you can remove them and there’s plugs that will plug the regulator ports, so you can just run a feed and a return line.”

Importantly, the Holley modules are designed to be E85 compatible, whereas the factory fuel pump can be suspect. “Some pumps have plastics in them that aren’t rated for E85. And you just need a lot more flow than what the factory system can handle in order for E85 to really be a feasible route.”