Eliminating A Classic Ford Bronco’s Fuel Injection Problems by Replacing Its Holley Sniper TBI With the Edelbrock Pro-Flo 4 Multi-Port EFI Part 1: Installation of the Edelbrock Pro-Flo 4 EFI Kit

To deliver a fair and unbiased report on why the owner of this classic Bronco wanted to replace the Holley Sniper TBI unit with an Edelbrock Pro-Flo 4 EFI, we referred to both the owner of the vehicle as well as the builder, Gateway Bronco. Read on to learn what they had to say about the two EFI systems and see how we installed a Pro-Flo 4 in the Edelbrock Garage.

Note: While this installation is performed on a classic Ford Bronco with a V-8 engine, most of the installation procedures and performance benefits of the Edelbrock Pro-Flo 4 apply to all vehicles.

You don’t have to be a Ford fan to appreciate the capability or cool factor of a classic Bronco, the “all-purpose vehicle” that paved the way for Chevrolet’s Blazer and Jeep’s Cherokee. The first-generation Bronco enjoyed a 12-year production run from 1966 through 1977 before it was revamped into a full-size SUV for the 1978 model year. The early Bronco was Ford Motor Company’s perfect off-road stablemate to their iconic Mustang ponycar that was into its second year of production in ‘66. The Bronco and Mustang were worlds apart in design, but they shared the same V-8 engine on the option list. While Jeep’s CJ-5 remained the top seller in the small 4×4 category, Ford produced nearly 35,000 Broncos in the first two years of production. At first, early Bronco buyers were limited to a 105-horse inline six for power, but when Ford added the 289-cubic-inch V-8 option shortly into the first year of production, the small-sized SUV became an instant hit among off-roading hot rodders of the era.

Mike Dorvillier’s Bronco Sport is a 1969 model, fully restored by Gateway Bronco in Hamel, IL. (Photo courtesy of Gateway Bronco)

Like many cars and trucks of the ‘60s, the classic Bronco is seeing a steady rise in both popularity and value as a collectible. In fact, a recent article from Haggerty reported that 1966-77 Broncos have increased in value by 200 percent over the past decade with no sign of slowing down.

Dorvillier’s Bronco is no run-of-the-mill build. Gateway calls this their “Restomod Fuelie,” one of three different versions of assembly-line restorations that you can order. The Fuelie is the hot rod version powered by a Ford 347-cubic-inch stroker with EFI. (Photo courtesy of Gateway Bronco)

While many Bronco owners stick with a utilitarian theme for their modern-day rebuilds, some guys like Michael Dorvillier want to take their on- and off-roading experience to the next level. For that, Dorvillier called upon Gateway Bronco, a facility with the space and expertise to build restored and modernized turnkey Ford Broncos on an assembly line. Located in the Midwest region of Illinois near Route 66, Gateway owner Seth Burgett oversees a team of experts who can produce any one of three different levels of badass Broncos depending on what your pocketbook can handle. Delivery time for a Gateway-built Bronco can be as short as two months, and all come with a warranty.

With prices starting at $95,000, Gateway Bronco buyers expect nothing less than perfection, both aesthetically and mechanically. According to Dorvillier and Gateway Bronco CEO/President Seth Burgett, there were just too many issues with the Holley Sniper TBI that couldn’t be solved, even with the help of Holley Tech Support. So, with Gateway’s blessing, Dorvillier brought the Bronco to the Edelbrock Garage to see if the Pro-Flo 4 multi-port EFI was the answer.

Dorvillier’s 1969 Bronco Sport is from the Gateway “Fuelie” line and, believe it or not, it’s the company’s base offering that starts at $95,000. The other two models in the Gateway lineup feature a 2018 Coyote 5.0L engine under the hood. Late-model Coyote power may be the ultimate for modern performance and reliability, but if you want a true hot rod version of the Bronco, then the Gateway Fuelie with a 302-based 347-cubic-inch stroker engine is the way to go.

The Edelbrock Pro-Flo 4 EFI System comes complete with throttle body and fuel rails preassembled on a single-plane manifold. The kit includes an Edelbrock distributor, ECU, gaskets, wiring harnesses, and even an optional Android tablet with the Edelbrock tuning app loaded.

The list of modifications and options on Dorvillier’s Gateway-built Bronco is as long as your arm with a fully restored and custom-painted Ford Bronco body, a custom leather interior, a stoutly modified drivetrain that includes the aforementioned warmed-over 347 Ford stroker backed by a four-speed automatic transmission, along with plenty of custom options. Up until recently, all of Gateway’s 347 engines have been fueled by Holley’s Sniper throttle body injection in an effort to add modern EFI drivability with a minimal increase in cost. But after experiencing numerous drivability issues with this and other builds with the Sniper TBI, all of that is about to change.

Owner Mike Dorvillier said the Holley Sniper TBI made the Bronco “a real chore to drive.”

Dorvillier was pleased with the power and torque that the 347 provided, but he was less than thrilled with the cold-start characteristics, stalling, and general drivability issues that the Sniper TBI-equipped engine exhibited. The stalling began to occur after Dorvillier took delivery of the Bronco so, under warranty, he sought help from an authorized repair shop in California who, after consulting with Holley, moved the idle up to prevent the stalling.

Edelbrock R&D tech Preston Rice began the Pro-Flo 4 installation by removing the Sniper TBI as well as the intake manifold, which happened to be an Edelbrock Performer. An MSD distributor was also tossed as was the Sniper wiring kit that was spliced into the Bronco harness.

The Sniper is a throttle-body injection unit (TBI) that supplies fuel through injectors located in the throttle body.  Aside from its slightly more appealing price point, another feature of a TBI kit like this is that installation can be relatively simple since it is a direct-fit, universal replacement for a 4150-style four-barrel carb and is sometimes the only solution for obscure engines that do not have a direct-port intake manifold available.

As you can see, there is nothing about a multi-port injection that is any more complicated than TBI. The Edelbrock Pro-Flo 4 EFI comes preassembled exactly as you see it here with throttle body and fuel rails in place. If you can install an intake manifold, you can install a Pro-Flo 4 EFI.

The cost factor never fails to raise this question: Are the few benefits of a TBI system worth the slight savings in cost, and more importantly, does the TBI system provide enough of an improvement over a carburetor to make it a worthwhile investment?

Learn more about the differences between TBI and multi-port EFI in this video from the Edelbrock USA YouTube channel.


 To get to the bottom of Dorvillier’s TBI problems, we went straight to Gateway Bronco, builders of the truck. According to Gateway President Seth Burgett, the problems that their engine department has experienced with the Holley TBI is not exclusive to Dorvillier’s Bronco. After no less than eight installations using the Holley TBI, Gateway has had key issues with each one. Burgett pulled no punches when he listed the problems that his engine department was having with the Holley Sniper TBI. The major issues were:

  • SYSTEM FAILURE – Premature failure of the Sniper system in the field. Following a proper tune, it would backfire on the customer and then fail to start. This occurred with two of the eight installations.
  • BACKFIRING, BOGGING AND SURGING – Tuning was erratic. Burgett said that after properly tuning, they would see lean conditions with backfire into the intake, hesitation at start, bogging under hard acceleration, and surging.
  • EXCESSIVE IDLE SPEED – High idle speeds were set by an authorized independent repair shop under warranty in an effort to prevent stalling when shifting into Drive or Reverse. (Burgett says that this solution was provided by Holley Tech Support and the repair shop, not Gateway Bronco.)
  • INCONSISTENCY – Throttle response with the Holley Sniper could be exceptional on one vehicle, but poor on another with the exact same engine, ignition, tires, transmission, and gearing.
  • BURGETT SAID that when they tried to transfer a Sniper TBI to another vehicle to determine where the problem was, the same issues would follow the TBI unit.

From a business standpoint, it was logical for Gateway Bronco to seek out the most cost-effective EFI system for their line of classic Bronco restomods. But after trying diligently to solve multiple issues with the Holley Sniper TBI, Burgett says that Gateway Bronco has transitioned exclusively to Edelbrock Pro-Flo 4 for their EFI systems.

While TBI kits continue to be a viable aftermarket EFI option for some applications, many high-performance engine experts and hot rodders in general are moving away from TBI in favor of multi-port EFI simply because they feel that TBI is a rudimentary system and nothing more than a glorified carburetor since it delivers fuel into the air stream at the plenum directly below the throttle body, just like a carb. With TBI, fuel is not equally distributed to all the cylinders, oftentimes puddling at the plenum. This means that the air/fuel mixture injected differs for each cylinder.

After meticulously cleaning all mating surfaces, Preston applies Gasgacinch to the cylinder heads to help hold the new gaskets in place.

A small bead of RTV silicone goes around each port on the manifold side of the gaskets and on the end seals.

The Edelbrock Pro-Flo 4 intake manifold and throttle body are then installed. The throttle body, fuel rails and intake manifold come preassembled in the Pro-Flo 4 kit. There is no need to disassemble them prior to installation. Scroll down to see the complete installation.

By comparison, the Edelbrock Pro-Flo 4 EFI is a far more precise method of fuel injection with individual injectors for each cylinder that are electronically synchronized with the intake valve opening events to deliver fuel into the air stream at the end of the manifold runners right before it enters the combustion chamber. This produces the absolute best fuel atomization with perfectly even distribution to each cylinder.

The multi-port design is so superior that, in 2017, Edelbrock discontinued production of their E-Street TBI kits in order to fully concentrate on the continued development of its Pro-Flo multi-port EFI product line.

So how much of a difference did the Edelbrock Pro-Flo 4 make compared to the Holley Sniper TBI on this classic Ford Bronco? Of course, we were just as curious as you are so after the Edelbrock-equipped Bronco was delivered to Dorvillier, we got in touch with him to get his initial impression of everything that he previously had issues with including cold-starting, idling, surging and stumbling under hard acceleration. This is what Dorvillier had to say:

It’s a night-and-day difference! I can tell you that after driving it around the area, and my son also took it for a spin around our community, it’s more enjoyable to drive. I’m not fighting the darn thing anymore. I’m just driving it and enjoying it.”

And the best part is that the Pro-Flo 4’s self-learning fuel technology will continually adjust calibration and improve engine performance as the vehicle is driven, with no laptop tuning required. The system will automatically compensate for altitude and weather changes, and through the E-Tuner app, you maintain full control with the ability to adjust air-fuel ratios, ignition curve, idle speed, acceleration fuel, cooling fans, rev limiter RPM, and more. Or you can simply monitor the engine vitals in real time from the optional Android tablet or your smart phone.

Since the Bronco was already plumbed with a fuel return line for the Sniper TBI, Preston moved the fuel lines to the rear of the Pro-Flo 4 fuel rails. This is a simple swap that takes just a few minutes.

Preston dropped the distributor in to check clearance with the kit-supplied crossover line. It was a tight fit so to be on the safe side, he made a longer line to clear the housing using Russell Twist-Lok hose and black-anodized fittings.

While not available from Gateway, another option for delivering high-pressure fuel to the EFI that eliminates the need for a return line is the Edelbrock Universal EFI Fuel Sump, seen here on one of the Edelbrock project cars. This is a complete self-contained system that can be installed under the hood of any vehicle to maintain consistent high pressure without the need to re-plumb the system.

This new Twist-Lok press from Russell Performance allows effortless assembly of custom lines that use Twist-Lok hose and fittings.

The 14-inch air cleaner on Dorvillier’s Bronco was not fitted with an air temperature sensor so Preston had to drill an opening for the 5/8-inch grommet.

The air temperature sensor was placed in a spot that would clear the manifold and not interfere with the throttle linkage.

Since the wideband oxygen (O2) sensor is responsible for sending important data to the ECU, we pulled the existing Holley sensor (left) and replaced it with the new one provided in the Edelbrock Pro-Flo 4 kit.

Preston installs the O2 sensor making sure to route the wiring away from the exhaust system and any moving parts of the drivetrain. The exhaust system must be properly sealed (i.e. no air leaks upstream of the sensor) and there must be at least 24 inches of exhaust pipe after the sensor for the ECU to read correctly.

The Pro-Flo 4 coil connection is a simple two-wire sub-harness connection.

Before the old distributor was removed, the engine was rotated to 12 degrees before top dead center (BTDC) with the number-one cylinder on compression stroke. The Edelbrock distributor is installed with the rotor pointing towards the number 1 mark on the housing. Always be sure to seat the distributor completely.

Next, the Pro-Flo 4 wiring harness is prepared for installation. A tidy harness without excess wiring is important for a custom look so Preston is carefully terminating the fuel pump connector here.

While the Sniper’s ECU concealed in the throttle body may look trick and ease the installation, remember that heat and electronics don’t play well together. The Pro-Flo 4 ECU is a small unit that Preston mounts on the backside of the right inner fender near the wiring harness and away from heat.

The plugs for each injector are clearly marked. Remember that “left” will always refer to the driver’s side and “right” is the passenger side.

After double-checking all of the connections and components, the battery is reconnected to perform the final steps of the installation. When you’re ready to proceed, switching the key on will send power to the ECU that will in turn cycle the fuel pump. At this point, check all fuel connections for possible leaks. If no leaks are detected, it’s time to pair the system with the tablet. When the E-Tuner is paired, you’ll see a green check mark that will replace the red X in the top right engine icon. Once you see the green check, you can proceed with the Setup Wizard.

After answering a few simple questions (engine type, cubic inches, firing order, cam profile) in the Setup Wizard, the system will then select the best map based on the information that you provided. The Setup Wizard will load the base map into the ECU and after another 10-second key-off-key-on cycle the engine is ready to start. Have a timing light ready for the first start-up so that you can set timing at 12 degrees and tighten the distributor. Once the base timing is set, you can make any fine-tuning adjustments in the app. The system will then select the best map based on the information that you provided.

Here’s an example of the Idle Tuning screen in the app. It shows throttle position at zero with an idle speed of 869 RPM. Touching the plus (+) or minus (–) button will set your target idle speed so that the ECU will know whether to raise or lower the RPMs to the desired idle speed.

This is the Digital Display screen that shows engine vitals as well as green indicators that show when the electric fan is on, when the system is in closed loop mode, and when the ECU is in the “learning” mode. The idle air control (IAC) is adjusted by the throttle screw to 5-15 percent at idle.

With all of the ECU parameters entered in the Setup Wizard and the engine idling at the target RPM, it’s time to drive and let the ECU self-learn and make its adjustments based on your particular driving style and environment. This data is constantly being monitored and updated into the ECU as you drive. The learned values are saved when the system is powered off for at least 10 seconds.

Now that Mike Dorvillier is enjoying the newfound drivability with his Pro-Flo 4 EFI Bronco, we’re going to give him time to really get used to the system and follow up with a long-term driving impression in a few weeks. So stay tuned here on the Edelblog!

For more information on the Pro-Flo 4 or other Edelbrock products, visit edelbrock.com.