Swapping carburetors for electronic fuel injection (EFI) is an excellent way to improve the drivability and fuel economy of your classic muscle car or truck. It’s also a powerful method to enhance the reliability of an older vehicle – and better reliability means you’ll spend more time enjoying your drive!
We asked Doug Flynn, Senior Systems Engineer for Fuel Injection at Holley, to share some insights on how EFI can reduce breakdowns.
“The biggest issue with carburetors is the composition of the fuel you get at the gas station,” he explains. “The fuel that’s blended today evaporates very easily, especially in the summer. If it’s hot enough, the fuel will boil and evaporate. With carburetors, that leads to a lot of problems with vapor lock. Maybe the engine doesn’t want to start, or it experiences inconsistent performance while driving. But with fuel injection, which is a closed system under high pressure, there’s no issue with fuel evaporation.”
“A second issue with modern fuel is that the ethanol content causes corrosion,” he continues. “You can end up with corrosion in the carburetor, leading to reliability problems. If the car sits for a long time and the fuel gets old, it’ll cause corrosion and contamination. The carburetor gaskets also harden, which can lead to additional problems.”
Variations in weather and altitude might not always lead to a breakdown, but they can cause issues with how smoothly a carbureted engine runs, requiring regular tuning and sometimes even a switch in setup from summer to winter. If installed and set up correctly, EFI removes climate variables by using sensors to automatically compensate for temperature, humidity, and altitude. This can be a huge advantage for owners who drive their classics regularly.
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According to Flynn, the right EFI setup involves more than just the injection system and ECU. Neglecting the fuel supply can undo the reliability benefits that fuel injection offers.
“Fuel tanks in older vehicles were designed for carburetors, not fuel injection,” he says. “I always recommend installing a new tank with an in-tank fuel pump and proper baffling.” Holley offers many solutions for this. “If you don’t go this route, you could run into problems when the fuel level drops below half a tank.”
“Pretty much every time someone uses an old tank, it’s full of contaminants. The EFI and the return line stir those up, and the next thing you know, the fuel pump’s dead and the filters are plugged. New fuel tanks are reasonably priced – often only a few hundred dollars. So, if a tank is available, it’s cost-effective and good preventative maintenance to replace it.”
“Inline electric fuel pumps don’t pull fuel well,” he adds. “An EFI high-pressure pump should be gravity-fed. If it’s pulling fuel up from the tank, the pump will eventually cavitate and fail. The fuel system needs to be ready for EFI, which is why I recommend a new tank and pump.”
For builders who’d prefer to keep the original tank, Holley offers the option to retrofit a new fuel pump and HydraMat. This patent-pending design uses surface tension and fluid wicking to prevent air from being drawn into the fuel system, which can cause poor engine performance, even with low fuel levels or during extreme use.
Flynn believes that an aftermarket EFI system, with a proper installation and a good fuel system, should be good for 100,000 miles without needing major maintenance. In comparison, a carburetor might require several rebuilds and new gaskets during that time.
In addition, the improved fuel economy – a 10 to 20% improvement is a reasonable estimate, depending on how well-tuned the carburetors were before – means that EFI not only pays for itself through saved maintenance hours but also at the pump. If you use your classic regularly, or like to drive long distances to shows, the savings will add up.
“If you drive your car a lot, the cold-start performance and drivability make a big difference,” notes Flynn. “It’s much better with fuel injection than with a carburetor. If you can make your old car drive like a new one, it’s just more enjoyable, and you’ll want to drive it more. EFI can also take a rowdy engine that’s difficult to drive with a carburetor and make it very enjoyable on the street.”
Flynn has also received feedback from racers that oil contamination is much reduced with EFI compared to carburetion, especially during rich running at cold temperatures. Not contaminating the oil with gas helps with motor reliability and longevity, which is important for race car drivers operating on a budget.
While a carburetor is inherently simple and can often be fixed with a few tools at the side of the road or track, taking proper care during EFI installation – despite its apparent complexity – means there will be far less routine maintenance going forward. The phone-app monitoring tools of products like the Sniper 2 EFI make it easy to keep an eye on the system and diagnose any issues.
“When you’re retrofitting fuel injection, the reliability is 90% based on the quality of your installation,” Flynn concludes. “You create the reliability. The wiring and the fuel system are key; if they’re done properly, your reliability will be high. EFI gives you the tools and components to ensure reliability, but it’s up to you to install it properly to take full advantage of that inherent reliability.”
