Photography By The Author and Courtesy of the Manufacturer
It’s natural to always want more, but sometimes too much of something isn’t a good thing. For example, using a camshaft or cylinder head that’s too big for your engine combination can result in lackluster performance and some serious head scratching. But there are areas in the automotive world where too much can be okay, and going big on a vehicle’s fuel system can earn a check mark versus a head shake. But before allowing yourself to think a Dominator carburetor is the ticket to more performance on a 400 horsepower small-block, cool your jets. By going big on the design of a fuel system and picking the right fuel pump and sizing the fuel lines correctly, the ability to change engines and still have room to grow into more power is achieved. As an added bonus, not taxing out any part of the fuel system keeps the amount of heat generated to a minimum.
Having roots dating back to the late 1,800s for tinkering with engines, Holley is credited with being one of the four original suppliers to Ford Motor Company. That dedication led to the introduction of the now-common 4150-series four-barrel carburetor in 1957, as well as the “blue” electric fuel pump that gained cult-like use starting in the early 1970s. Today, Holley stands as one of over 20 brands under a single umbrella, with over 300 part numbers in the fuel pump and regulator segment alone. That can easily lead to confusion over what parts to choose for a fuel system, but with Blane Burnett from Holley and Jason Rollins of Rollins Automotive Speed and Custom in our corner, we can attempt to tackle the mysteries of fuel systems.
“The key to understanding fuel systems is identifying your key factors,” said Rollins. “You need to establish the type of induction system, projected horsepower, and how the vehicle will be used.” With that knowledge in hand, a game plan can be designed. “You want to consider the type of fuel system the vehicle already has on it,” said Burnett, adding that will influence what pump options exist. “It may be easier to purchase a pump rated for higher horsepower that is a factory drop-in replacement unit that requires no modifications to the rest of the system for installation.” But in our case, a complete revamp of the system and possible four-digit power in the future meant selecting a pump that can handle a lot of load.
“Holley’s Dominator pump is designed with two separate veins/motors, so it can be set up to accommodate different needs,” said Rollins. “You could run one side for daily driving, or pit use only for a race car if needed. This will keep the heating of the fuel down versus using both when the volume isn’t needed. The second motor/vein can be routed to a toggle switch, a boost-referenced switch, a wide-open-throttle switch or even an ECM trigger when running fuel injection to bring it in.”
With the fuel pump selected, the next step is to map out how the fuel system will be run. Keeping fuel away from heat and moving parts might seem easy enough, but doing it without excessive twists and turns in the fuel’s travels from the tank to the engine can be difficult.
“Hard 90-degree forged fittings are sometimes a necessity in the tight confines of an engine bay, but they should rarely be used due to the flow restriction,” Burnett admits. “Compared to a 90-degree tube fitting, a hard 90-degree forged fitting is like adding eleven feet of line to a fuel system. Using fittings that require less changes in direction and take the least hard angles is always the way to go.”
The next decision is whether to use a return-style system or a return-less version, and while Burnett believes it is personal preference, Rollins normally goes for a return-style set-up.
“I’ve seen more consistent fuel pressures on a return-style system, especially with carburetors,” Rollins admits.
Choosing the correct line and size can be a common problem as well, and operating pressure and fuel choice will dictate your parameters.
“Typically anything under 600 horsepower can be adequately supplied by -6 AN or 5/16-inch line,” said Burnett. “Above that mark, it is common to upgrade to -8AN.” But choosing E85 as a fuel choice will shift those recommendations. “All things being equal, an engine that that uses E85 requires 30 percent more fuel to supply the engine over traditional gasoline,” said Burnett. Fuel injection and boosted applications also raise fuel line requirements, and going to a slightly larger line is better than restricting the system’s ability to function.
“BSFC, or Brake Specific Fuel Consumption, is why fuel pumps are rated differently for EFI and boosted applications over a naturally aspirated carbureted one,” said Rollins. “Boosted and EFI systems can require 10-15 percent more fuel volume, and that requirement should also be figured into line selection.”
Building a turbocharged powerplant with a target goal of 850 horsepower as a starting point, Rollins wanted to build a fuel system that would not only handle the engine’s initial power level, but also be able to move beyond it.
“You need to look beyond your current status and not build a system that could be obsolete in a year,” said Rollins. “Doing a fuel system can be tedious, so taking a little extra time to make sure the right components are used, the right amount of line to cover it, and all the different fittings needed can mean the difference between an easy day and pulling your hair out. Even if you’re starting from scratch, the right parts and a clear vision means a system can be assembled in just one day, even if it’s on jack stands in a driveway.”