The Terminator X EFI line has always been aimed at giving street machine builders everything they need and nothing they don’t, in turn providing a system that keeps the setup simple and the costs low. While the original Terminator systems marked Holley’s first foray into throttle body injection systems with a motorsport-ready ECU, the company also noted the benefits of a TBI system with an ECU setup that focused on the fundamentals.

“We realized that there’s a sizable portion of our consumer base that wants to use a throttle body EFI system but doesn’t necessarily need all of the features that a Dominator ECU offers,” explains Colin Kinser of Holley Performance. “At the same time, they might also may need a wider feature set than our Sniper EFI systems can offer.”

And that’s where the Terminator X has helped to fill an important niche over the past few years. Now that same philosophy comes by way of the Terminator X Stealth 2x4 kits, which deliver those capabilities in a dual 4BBL carb-style setup for a period correct look that can support big power.

The Terminator X Stealth 4150 2x4 kit comes ready to install. All you need to have is a fuel system that can support EFI fuel pressures (43-58 PSI) and Holley recommends an ignition system that has timing control, such as the Sniper HyperSpark systems.

“The Sniper systems have been popular with those who’re looking for a straight-forward carburetor replacement EFI setup for a while now,” Kinser says. “We also released a Sniper 2x4 kit a few years ago, and that has been extremely successful in its own right. But there were those who wanted a similar dual carb-style EFI system that offered a wider array of features while also really retaining the look of a carburetor.”

Designed to mimic the classic look of conventional double-pumper while supporting up to 1500 horsepower, these systems bring all of the benefits of a Terminator X system with a layout that retains the old school cool of a dual carb setup.

Get In And Go

“I think this is really going to appeal to the street guys and anyone who wants to pop the hood at car shows,” Kinser tells us. “And it’s also a cool option for the folks who’re looking to support a lot of power with a dual setup. It’s great for blower applications – if you’ve got a roots-style blower that a dual 4150 flange, which is pretty common with a 6-71 or an 8-71, this is going to be right at home. And in that respect, there could also some racing applications where this setup would make a lot of sense as well.”

While a cross-ram manifold with a pair of four-barrels bolted up to it is a compelling nostalgic vibe, there’s a lot to be said for the benefits of modern technology. “Dual carbs are fun, but some people don’t want to deal with the tuning issues that are inherent to that kind of thing,” Kinser points out. “With fuel injection you don’t have worry about elevation, temperature changes, float adjustments, or anything like that – it’s EFI. And if it’s a vehicle that gets driven occasionally, it can make a lot of sense to pull the carbs off and swap this system in to have the ability to just turn the key and head out.”

The Terminator X Stealth 4150 throttle body units are designed to be a bolt-on replacement for the standard 4150 carburetor.

Kinser notes that the kit is designed to work in this 2x4 configuration right out of the box, so there’s no individual setup or tuning required to get the pair of throttle bodies working in harmony.

“It uses a unique harness versus the single throttle body Terminator X Stealth EFI system, but the tuning is just as straight forward. Here you have a primary throttle body that has four 100 Lb/Hr injectors, and that primary throttle body houses the throttle position sensor and the idle control valve. The secondary throttle body is just an air valve, so it has the throttle plates in it and four 100 Lb/Hr injectors – no other control parameters are on it. When you’re tuning it with the hand-held or a laptop, the ECU is pulling the fuel out across all eight injectors, so it’s not something where you need to mess with each throttle body individually to get everything running right.”

As with all Holley EFI setups, it’s a self-learning system that only requires some basic information to get up and running – no laptop required. “The calibration wizard will ask you about what your ignition setup is and whether or not you’re doing timing control. If you are doing timing control, it’s going to ask whether it’s magnetic or if it’s one of our products like the HyperSpark or Dual Sync. From there it will ask for fuel system information as well as a few basic engine questions such as whether your camshaft is considered street, mild street/strip, or race cam. That’s basically so the ECU knows where to look on the map for idle.”

Above And Beyond

Aside from its Stealth look, the Terminator X 2x4 systems offer several key features that the Sniper EFI 2x4 systems do not. “The biggest one is probably transmission control,” he says. “If you have a 4L60, 4L70, 4L80, or a Ford 4R70W handling the gear changes in your vehicle, the Terminator X kit allows you to program and control the transmission in terms of shift points, line pressures, and torque converter lockup.”

The Terminator X Stealth 2x4 system also offers more inputs and outputs, allowing you to expand the system’s capability to provide nitrous control, water-meth control, and other auxiliary systems. And of course the system is also plug-and-play compatible with a range of Holley EFI products like the 12.3” and 6.86” Pro Dash displays, the CANBus EGT kit, and the analog-style digital gauges.

Don't worry if the wiring harnesses that come with the Terminator X kit look intimidating. Between the instruction book and the clearly identified connectors, wiring will be a simple, straightforward affair.

In terms of engine applications, these kits are ostensibly universal. You’ll want to have an upgraded, electronic ignition system and you’ll need a fuel system that can support EFI fuel pressures to support the Terminator X system properly, but Holley’s got you covered there, too. “You can run it without timing control, but that’s generally not a great idea,” Kinser says. “An ignition system like the Sniper HyperSpark would work perfectly here, and our retrofit fuel systems will provide that high pressure that you’re going to need if you’re switching over from a carbureted setup. Carbureted systems usually need six to eight PSI to run, but an EFI system is generally going to need either 43 or 58 psi. We have replacement tanks that have EFI-compatible high pressure pumps built in, or you can also opt to run an external in-line pump.”

The systems are available in polished, black, and gold finishes as well as dual throttle body setups that come without injectors. “The air valve setups are mainly for customers who want to have the look of a carbureted system instead of a forward-facing traditional throttle body while running mutli-port fuel injection,” Kinser says.

"So they have a multi-point intake manifold with injectors per cylinder, and you’re using fuel rails to deliver that fuel into the cylinders. But since you’re using these carb-style throttle bodies you can use old school air cleaners, so when you pop the hood it’s all going to still have that period correct vibe.”

The LCD touch screen that comes with the Terminator X kit is your gateway to preparing the tune for your vehicle. Using the Calibration Wizard, just input your ignition system type, whether you are using timing control or not, basic fuel system information and a few basic engine questions, and the ECU will use the information so that the first twist of the key results in a running engine.