Everyone knows that electronic fuel injection is great, but messing with computers, wires, a new intake manifold, sensors, and having to program it on a laptop makes dealing with tuning a simple carburetor much more appealing. Many owners of older cars equipped with a two- or four-barrel carburetor, would rather put up with hard starts in the morning and changing power valves to optimize fuel during winter and summer seasons, than deal with the difficulty of upgrading to an aftermarket electronic fuel injection system.
But the fact is that many aftermarket EFI systems have become much easier to install and tune. Easier still is Holley’s Avenger EFI system that doesn’t even require a new intake manifold and can literally have you swapped from a carburetor to EFI in a matter of hours. The Avenger EFI system is unique, as it replaces any carburetor with a computer-controlled throttle-body injection system. What’s more is that the TBI unit simply bolts onto your existing intake manifold so there’s no need for new gaskets, draining the coolant, and all the extra expenses.
Despite the fact that it’s a throttle-body injection system and not a multiport EFI, (Holley makes those too) the Avenger EFI is powerful enough to work with a variety of engine and horsepower applications from 275-600 hp and with cfm ratings from 600-900 cfm. So it can work on anything from a Chevy 250ci inline-six, a street-performance small-block 350 V-8, or a 502 big-block bracket-race motor.
Installation is simple and we looked on as Rob Green, of JKR Racing in Orange, California, installed the Avenger EFI system onto a ’61 Corvette that was being built as a performance street vehicle. One of the first things Green had to do was create a fuel return line for the system. Fuel injection systems provide constant pressure to the injectors, and a return line ensures that the system doesn’t get starved (vapor lock) or over pressurized with fuel.
Green used Earl’s AN-8 stainless steel braided fuel hose that would eventually attach to the outlet of the throttle body and connect to a hard stainless steel line he bent, which runs alongside the frame. The line feeds into another braided piece of fuel hose that goes back into the tank. In this case the Corvette uses a fuel cell located in the trunk and has AN fittings for both a fuel inlet and return line already on it. If you have an OEM fuel tank, you can simply purchase a return line adapter that fits between the rubber filler neck of the tank. Moroso makes a nice one (PN MOR-6535) that’s made from aluminum tubing and retails around $40.
Holley’s Avenger EFI system comes with a high-pressure inline fuel pump that must be adapted to your vehicle’s existing fuel line. In this case, the Corvette already had an electronic pump with a separate regulator. Green removed both and replaced them with the new Holley electric pump supplied in the kit. After finding a suitable location away from the exhaust, he mounted the new pump to the frame using the isolator clamps provided in the kit. A fuel filter is also included, and Green plumbed it all together using stainless braided hose and the appropriate AN-8 fittings. Once he was done, both the fuel line and return line now run directly from the fuel cell, along the inside of the frame and up to the throttle-body.
The engine in this application was a 427ci small-block stroker that was outfitted with a four-barrel carburetor on top of a Weiand Street Warrior dual-plane intake manifold. Swapping it was only a matter of unbolting the four-barrel carburetor and bolting on the new Holley TBI unit. The fuel inlet hose was attached to the rear of the throttle-body, which already has a pre-adjusted fuel pressure regulator. The new fuel return line was then attached to the outlet on the throttle body that leads back to the tank.