Mark Houlahan
Tech Editor, Mustang Monthly
February 28, 2014

Holley is no stranger to delivering fuel to an internal combustion engine. Holley has been designing and building fuel delivery hardware since 1903 when Henry Ford himself asked the Holley brothers to build a carburetor for his new Model A he was building. From that first Model A to the 4150 four-barrel found on the '57 Thunderbird to generations of Mustangs with factory OE Holley carbs (and many more with aftermarket Holley four-barrel carbs) Holley and Ford have had a century long relationship.

When it comes to aftermarket fuel injection Holley has had their foot in that door for a long time, believe it or not. From early TBI-style conversions to performance EFI parts for late-model Mustangs, Holley is far from a newcomer to aftermarket EFI. The company has offered its Avenger EFI systems for a few years now and these systems offer a great way to update your driver with EFI. Alongside the Avenger EFI is Holley's HP EFI systems, which offer a head-swimming array of options for inputs/outputs that is the perfect solution for the drag racers out there or for people with complicated setups (supercharged, electronic transmissions, using OE-style EFI intake manifolds, and so on) but for the typical user the 16 or so decisions you have to jump through for ECU, harness, ignition, and more is a bit of a pain.

Holley's Dominator EFI, which is the next step above the HP system, is similar and for a typical small- or big-block Ford that is street driven with no power adders, trans brake, or other options these systems are overkill. Bolting an EFI throttle body down onto a four-barrel intake and connecting a few wires is what today's aftermarket EFI consumer is looking for. The throttle body systems found under the Avenger and HP lines do bolt to said intakes, but the programming and tuning takes a steeper learning curve, but that's also because they do so much more. Enter Holley's new Terminator EFI system.

The Terminator system uses a brand-new billet throttle body design that is similar to the one employed in Holley's new NASCAR EFI throttle bodies. This design features maximum air velocity into the engine with the injectors in a horizontal mounting position feeding into a quartet of annular fuel rings beneath the throttle plates. Unlike traditional TBI-style systems with the injectors above the throttle plates, which can induce delay and restrict airflow, these rings allow for the fuel to atomize better. This improved atomization increases fuel economy and performance.

While this new hardware is a huge improvement over past bolt-on EFI conversions it is only half the solution. The other half is the software and wiring. Holley's Terminator EFI uses a similar ECU to its big brother "race" systems, yet is streamlined for easier installation with fewer hassles. The Terminator EFI's basic options include the ability to control two cooling fans and to shut the A/C off at wide-open-throttle (WOT) like modern cars do for increased performance with less drag on the engine. The pre-terminated harness makes for quick wiring with just a few wires to connect and with the proper distributor the Terminator ECU can even control ignition timing. Finally, Holley uses its full color OELD handheld tuner with the Terminator system, so no laptop is required. Simply answer a few questions and let the self-tuning feature take over. Of course, if you simply can't resist tinkering there are several tuning options that can be adjusted from the handheld tuner to further tweak stubborn engine combinations.

Lest you think this system is only for stock engines, fear not, as the 80-lb/hr injectors and 950-cfm throttle body are cable of handling any engine from 250 to 600 horsepower. Of course you have to have the appropriate fuel system to support said horsepower and Holley has you covered there as well with four different EFI fuel system kits. Finally, if you do need the options and tuning capability of a more advanced EFI system in the future, the Terminator EFI ECU can simply be upgraded to the Holley HP EFI ECU's specs with a free software download from Holley's website. With the free upgrade you'll be ready for nitrous, a supercharger, or other performance enhancements.

1 The Terminator EFI system ships as a fully assembled throttle body. There’s nothing to do to but bolt it to your four-barrel intake manifold. Included with the system are pre-terminated wiring harnesses, the ECU, a wideband oxygen sensor, and the handheld tuner. The only kit options are throttle body finish—Hard Core Gray or tumble polished.
2 The Terminator system is designed to be used with a high-pressure EFI return-style fuel system. Holley makes it easy with a system-matched kit available as an option with pre- and post-filters, a fuel pump, a regulator, fittings, EFI-rated hose, and even a fuel pump block off plate. There are four fuel system options and we chose the PN 526-2 with billet pump and filters and Earl’s Pro-Lite 350 hose.
3 Typical of most classic Mustangs today, this ’65 coupe was running an Edelbrock intake and Holley four-barrel carburetor. The Air-Gap manifold will work fine for our conversion but first the old Holley squirter has to go! Remove the four carb retaining nuts but don’t pull the carb just yet.
4 To prevent spilling fuel on the freshly painted intake (even without paint fuel can stain a bare aluminum manifold) the fuel feed line from the mechanical fuel pump was disconnected so that the carb and feed line could be removed as an assembly.
5 Now, while holding the fuel line higher than the carb, the carb and fuel line are lifted off of the engine. Cover the manifold inlet with a shop rag or some wide painter’s tape for now.
6 The mechanical fuel pump is added to the spare parts pile next. Remove the two attaching bolts, disconnect the fuel feed line from the pump and snake the pump out of the timing cover. When installing the included block-off plate shorter bolts may be necessary.
7 This ’65 had a custom 3⁄8-inch aluminum fuel line and hidden fuel filter in the left front fender apron area. While we could possibly have used it for the new EFI system we felt it best to strip the car of all old fuel lines and run new lines once our pump and filter locations have been confirmed.
8 With the Mustang stripped of all old fuel system parts it is time to crack open the Holley Terminator box and start installing our shiny bits. First up is the throttle body. Remove the shop rag or tape you had used to prevent ingestion of small parts to the intake manifold and slip the throttle body down over the studs. New studs are included if your existing ones aren’t the correct length.
9 Mounting the ECU in the car should not present too much of a challenge. The unit is slightly wider than your typical CD ignition box and can be mounted inside (preferred) or under the hood. If mounting under the hood ensure the connector face is pointing down or away from potential water splash. Be sure to use the included mounting hardware and pre-installed insulators.
10 Once the ECU is mounted the ECU’s main wiring harness can be roughed in between the ECU and the throttle body. Begin by connecting the two ECU main input/output connectors, labeled P1A and P1B to the ECU and then route the harness to the engine, keeping it away from direct heat and moving parts. The third connector (not shown) includes the heavy gauge power and ground wiring that is routed directly to the battery and terminated there with the included ring terminals and shrink wrap.
11 All sensors and actuators are integrated into the throttle body assembly except for the engine coolant temperature sensor (ECT) and the wideband oxygen sensor. The ECT needs to see coolant temp from the main water passage in the intake. Do not install the sensor in the radiator, rear intake ports, or in the thermostat housing.
12 On most manifolds there are but two such ports in the main water crossover—one for the heater hose fitting and one for the gauge sender. To solve the problem of needing three ports with EFI some people use the late-model Mustang metal heater tube (with ECT fitting in it). Another option, if you have a 1⁄8-inch gauge sender, is to drill and tap the top of the heater elbow to relocate the gauge sender. We did this on our Factory Five Cobra build many years ago with no issues.
On most manifolds there are but two such ports in the main water crossover—one for the heater hose fitting and one for the gauge sender. To solve the problem of needing three ports with EFI some people use the late-model Mustang metal heater tube (with ECT fitting in it). Another option, if you have a 1⁄8-inch gauge sender, is to drill and tap the top of the heater elbow to relocate the gauge sender. We did this on our Factory Five Cobra build many years ago with no issues.
13 After routing the harness and connecting the ECT on the engine the remaining connections require attention. There are two CANbus connectors near the ECU. This CANbus terminator is plugged into the second one.
14 The handheld tuner is then plugged into the first CANbus connector. The red/white stripe wire near the CANbus connectors requires power in START and RUN and is best routed directly to the ignition switch.
15 From the grommet in the inner fender the handheld tuner harness and the red/white stripe wire are routed along the top of the fender (in the wheelwell) and then pass through this owner-installed grommet in the firewall used to hide the engine bay wiring.
16 The Holley Terminator system can use a late-model Ford Thick Film Ignition (TFI) distributor from a 5.0L Mustang with a special adapter harness sold separately. However, if you already have a capacitive discharge ignition box (MSD, Mallory, and so on) the supplied plug-in adapter’s single yellow/black wire needs to be connected to the “tach” terminal on the ignition box, which the owner had installed on the firewall inside the car.
17 The ECU harness does have four loose wires that require termination/routing to complete. The red and black wires are power and ground respectively, while the green wire is power to the fuel pump. The yellow wire is for some ignition systems but not being used on this installation and will be capped with shrink wrap.
18 The red wire is a hot-at-all-times connection and it was routed to the battery stud on the nearby alternator. The green wire for the fuel pump followed the heater hoses rearward off the back of the engine, while the ground wire was connected to the throttle body mounting bolt/stud, seen here.