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Holley Sniper EFI Meets Old Jeep

Posted in How To: Engine on July 25, 2017
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They say once you taste steak, it’s hard to go back to just eating hamburger. Such is the case with electronic fuel injection versus basic carburetion. So, what if you have an older carbureted Jeep that doesn’t quite warrant an engine swap, but you want more of what a modern fuel system can provide. You know: easy cold starts, smoother idle, increased power, and better fuel economy. Well, Holley may have your answer.

The 1969 Jeepster we used for this exercise in modern fuel delivery was powered by the venerable, but still carbureted, Buick 261ci V-6, a common enough engine in Jeeps of the day. It had occasional problems with cold starts, plus it stumbled badly when climbing hills. The latter killed a lot of the fun factor when out wheeling. The owner chose to upgrade the fuel system with a Holley Sniper EFI Self-Tuning Kit. The throttle-body system flows up to 800cfm and supports naturally aspirated engines making up to 650 hp. It has an integrated fuel pressure regulator, along with the ability to function with a wide variety of OEM and aftermarket ignition systems.

The engine control unit (ECU) inside the throttle body assembly will tune itself with a self-learning technique. The user can also override many of the parameters using the 3.5-inch display controller that comes in the kit. The ECU is highly customizable and includes rev limiting, nitrous injection control, and many fuel mapping functions.

A complete wiring harness is included, and the only external connections needed are battery positive, switched ignition, tach signal, and ground. It has the ability to control electric fans, interface with an air conditioning relay, and drive an aftermarket tachometer or Holley EFI analog gauges. A wideband oxygen sensor is used to monitor exhaust composition and provide data to the ECU to further tune the fuel map for the particular engine.

With the hardware and wiring install complete, we turned on the ignition and followed the setup instructions in the Calibration Wizard software using the handheld controller. It walked us through a series of questions about the engine it was attached to. Once it set up a baseline fuel map, we were instructed to fire up the engine. It started almost immediately and soon settled into a nice base idle speed.

After a short adjustment of the idle settings it was time for a test drive. There was initially a bog off idle when stepping on the gas. However, the ECU quickly starting learning once the engine hit normal operating temperature and smoothed everything out. Driving the V-6 powered Jeepster quickly revealed a smoother running engine with more power under throttle than it ever had with its previous 4-barrel carburetor.

Holley’s Sniper EFI Kit came with everything to hook up fuel connections, ignition, electrical wiring, and an oxygen sensor. Initial installation time took just less than 8 hours and we had the Jeepster running again.
The ECU is mounted within the Sniper EFI throttle body assembly so there are no other boxes or modules to mount. Up front are two of the possible three fuel inlet locations that are available.
Another fuel inlet location was located on the rear along with the fuel return outlet. The assembly had an idle air control (IAC) valve connected to the harness to control idle speed and quality.
A 3.5-inch color, touchscreen controller was used to walk us step by step through initial setup and tuning. It then can be used with gauge sets to monitor a large number of operating parameters.
Here’s what we started with in the ’69 Jeepster. It had a Buick 231 V-6 that was topped with an Edelbrock 4-barrel carburetor sitting on an Edelbrock intake manifold. The engine also had a GM HEI electronic ignition.
We began by disconnecting the throttle linkage, vacuum lines, choke wiring, and fuel lines before unbolting the old carburetor. The Sniper throttle body mates to any 4-barrel, 4150-style square flange or universal flanged spread-bore manifold.
The system ECU monitors the engine coolant temperature to make fuel mixture changes. We installed a coolant sensor provided by Holley in a threaded port in the intake manifold. The Holley touchscreen controller displays coolant temp using this sensor, but we also retained the factory sensor to continue use of the stock analog dash gauge.
Holley provides several common throttle-cable ends to place on the linkage. Our old carburetor had a ball stud so we installed a matching one on the Holley throttle body.
We bolted the new throttle body in place on the manifold using the supplied gasket and reconnected our vacuum lines to the available ports on the base of the Sniper throttle body.
The throttle cable assembly was installed using the old return spring. Holley’s kit provided several throttle and transmission kickdown cable brackets. We easily modified one to support our existing throttle cable.
The Bosch wideband oxygen sensor needs to be mounted close to the exhaust manifold. We found a good location just below the manifold flange, one we could access from under the front fender. It was necessary to drill a 3/4-inch hole for the Holley-provided saddle mount that clamps the oxygen sensor onto the exhaust pipe. No welding is needed.
We connected fuel supply and return lines to the throttle body using fittings and the high-pressure-rated fuel-injection hose provided by Holley. Lines can be plumbed straight or with elbows that are included in the kit.
Here’s the pump and filter assembly built using the supplied parts. A 40- to 100-micron pre filter (right) was used before the inline pump, followed by a 10-micron post filter. Fuel pressure in the system was 58.5psi and the injector size was rated at 100 lb/hr. A mechanical fuel pump block-off plate was included in the kit as well.
It’s possible to transition the fuel supply and return paths to steel lines, but Holley provided plenty of rubber hose so it was routed up high along the frame rail and run back to the fuel tank area. The pump and filters were mounted at the rear of the Jeepster near the tank using some clamps that were purchased at a hardware store. Holley also provided a bulkhead fitting to install on the fuel tank should it be needed.
Next, the harness was fitted under the hood and connected to the throttle body. These are the inline fuse and fuel pump relay on the harness. We mounted them to the inner fender with a couple of screws. Holley recommended that the harness be connected directly to the battery terminals. We kept the GM HEI ignition intact and let it control timing for the engine.
The only wiring that needed to go into the interior was the cable for the controller. Holley provided a large firewall grommet, but we found an available grommet on the firewall and passed the wiring through it.
The controller can be used for programming and tuning, as well as to provide a good variety of display modes. Gauge displays can be customized to show the parameters you are most interested in seeing.


Holley Performance Products
Bowling Green, KY 42101

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