MSD Atomic EFI On A Big-Block - Splitting The Atom

Ditch That Carb

Harry WagnerPhotographer, Writer

Wheeling has changed a lot through the years. Bigger tires, lower gearing, and fuel injection are mainstays nowadays. Electronic fuel injection (EFI) comes on every new vehicle, but that was not always the case. When we dusted off the family heirloom (literally) the first thing he wanted to add was MSD’s Atomic EFI. While fuel injection usually runs cleaner and generally delivers better mileage than carburetors, neither was the deciding factor for this upgrade. Our ’67 FJ40 is smog exempt, and it is a fool’s errand to expect the 468ci big-block under the hood (that’s right, I said big-block) to sip fuel with a massive four-barrel carburetor.

So what was the motivation? Fuel injection allows an engine to run at any angle on the trails, starts up easily, and automatically adjusts for different elevations and temperatures, unlike a stock carburetor. These situations are common to off-roaders and are on the radar for the Cruiser’s future. However, some fuel injection systems have a reputation for being complicated and difficult to install. All of that changed with MSD’s introduction of Atomic EFI. With half the connections of other systems, MSD claims that its product can be installed in a day. That may be true for a professional mechanic in a fully equipped shop, but could it be done by a couple of guys with basic handtools in a two-car garage? We wanted to find out.

The kit we ordered (PN 2900) is rated to support up to 525 hp and includes the throttle body, power module (with wide band O2 sensor), handheld controller, fuel pump, fuel filters, and all related wiring and hardware. If you already have an electric fuel pump capable of delivering the required 60 psi to the Atomic throttle body, a kit is also available without the fuel pump and is even easier to install. MSD engineers have incorporated most of the input sensors into the throttle body, which makes the system compact and clean-looking—perfect for our classic Land Cruiser.

The throttle body actually houses the ECU and incorporates the throttle position sensor (TPS), manifold absolute pressure sensor (MAP), intake air sensor (IAT), and fuel pressure sensors in one location on the right side of the unit. Also integrated into the throttle body are internal fuel rails that provide fuel to four 80-pound/hour fuel injectors, one at each corner of the throttle body.

Even with a few unforeseen challenges due to our unique drivetrain combination, we were able to install MSD’s Atomic EFI in a day at home in the garage. Once wired and plumbed the system fired right up and idled smoothly. With just basic input parameters and with the self-learning capabilities of the system, the throttle response and idle continue to improve with every mile we drive. We can now enjoy consistent fuel delivery at any angle on the trail and didn’t have to spend four years getting a degree in electrical engineering to do it.

Return or Returnless Fuel System?
Atomic EFI has the option to be installed as either a return or returnless fuel system. Returnless is the easiest to install because you only need to run a fuel line from the tank to the electric fuel pump and up to the throttle body. In contrast, a return-style fuel system uses a regulator and a second line running back to the tank with any excess fuel.

Several factors will help you determine which is best for you, including quality of fuel, ambient temperature, and distance of the fuel pump from the tank. While our parameters put us on the edge of the ability to use the returnless system, we chose it simply based on ease of installation with our existing fuel tank.

Adding a fuel pump in the tank and/or a return fuel line and regulator is more complicated. However, it will virtually eliminate the possibility of fuel pump cavitation (with symptoms similar to vaporlock) in hot conditions. If our installation creates issues in the future we will be certain to remedy the fuel routing and let you know.

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