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We make a 1964 Chevelle more reliable and efficient with Holley Sniper EFI

Effortless EFI: We Wake Up a Sleepy 283 with Holley’s Sniper EFI System

Tommy Lee Byrd Nov 27, 2017
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The popularity of modernizing a classic Chevrolet is undeniable. The automotive aftermarket supports the modifications with lots of great parts that allow you to bolt modern technology to a vintage platform. And while LS swaps are commonplace, a good old-fashioned small-block Chevy can be treated to modern technology and still retain its nostalgic nature. In our case, we’re dealing with a bone-stock 283ci small-block Chevy under the hood of a 1964 Chevelle. This engine has never been cracked open or messed with, so it’s a great application for daily driving, especially when we replace the leaky and wheezy Rochester two-barrel carburetor.

Our choice for a modern induction system is a Holley Sniper EFI system. The system bolts to any manifold with a four-barrel carburetor flange, and will work on a 600-horsepower stroker as well as our 200-horsepower stocker. The beauty of the system is that it tunes itself as you’re driving down the road. It’s fully configurable to your own custom settings, but it’s also equipped with default settings that can get you wherever you need to go. For our setup, it made the most sense to include a Holley EFI-ready fuel tank with our Sniper system so the fuel pump would be submerged in the tank for quiet and reliable operation.

The combination of the EFI-ready fuel tank and the Holley Sniper EFI system offered an easy and clean installation. We wanted the old-school engine to have the right look so we took the opportunity to clean the engine and outfit it with some fresh Holley accessories while it was apart. Without a close visual inspection, you’d never know the car has fuel injection, but the ease of operation makes it quite obvious that we’re no longer dealing with an old Rochester carburetor.

After the Holley system tuned itself and we tweaked a few of the air/fuel ratio settings, it was time to put some miles on the refreshed 283, and we did just that. Cold start and hot start behavior improved greatly. We also noticed a small bump in average fuel mileage, going from 16 mpg to nearly 18 mpg. Given the upgrade to an aluminum dual-plane intake manifold and the precise fuel curve of the Holley Sniper system we undoubtedly gained horsepower but didn’t feel the need to twist the guts out of the tired 283 on the dyno. After all, this install isn’t strictly about power and torque—it’s about user-friendly technology that can bring any old-school engine into the modern era.

We installed the system in our garage with standard tools that are mostly likely already in your toolbox. If you’re doing the fuel tank and the Sniper system install like we did, set aside a couple of good weekends in the shop to make the conversion. Whether you’re dealing with a bone-stock engine like this one or a rowdy Saturday night special, this Holley Sniper EFI system is a bolt-on solution to fuel system tuning that you can install and tune at home.

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1. Our starting point is the original 283ci small-block in our 1964 Chevelle. We’ve already installed a new water pump, electronic ignition, Vintage Air A/C, and a Powermaster one-wire alternator. It’s time to wake up this sleepy Mouse motor with Holley EFI.

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2. The original air cleaner goes to the swap meet pile, and the old Rochester two-barrel carburetor isn’t far behind. Despite a recent rebuild, it still leaked and had an off-idle hesitation.

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3. Before we get too carried away, we spin the engine over to the timing mark to make sure it is on top dead center before we remove the distributor and continue the disassembly process.

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4. One of our first modifications to the 283 was an electronic ignition system. And since the Holley Sniper EFI is compatible with our current distributor, we’ll be reusing it, but freshening up the ignition system with a new coil and plug wires.

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5. After removing the upper radiator hose, heater hose, throttle linkage and fuel line, we yank the cast-iron intake and Rochester two-barrel carburetor. Judging by the condition of this car, this is probably the first time the intake manifold has been removed.

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6. We stuffed rags into the ports and scraped gasket material until the cylinder heads were clean. With more than 50 years of heat cycles the gaskets were baked on, but a sharp putty knife did the trick.

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7. Replacing the original cast-iron intake manifold is this Weiand Street Warrior dual-plane aluminum intake (PN 8150). It was a no-brainer to go with an aluminum intake versus a stock-style cast-iron unit for weight savings, a clean appearance, and, of course, a four-barrel flange for easy installation of the Holley Sniper EFI system.

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8. Using a combination of Fel-Pro gaskets and Permatex RTV on the ends, we create a welcoming environment for the new intake.

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9. We carefully lower the intake manifold into place, being sure that our bolt holes are lined up and that we don’t damage the beads of silicone.

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10. After grabbing a new engine bolt kit from Summit Racing, we installed the new hardware and tightened it while the silicone was still pliable. We start by tightening the four bolts closest to the carburetor flange and then working our way outward.

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11. We want to get the water flowing as soon as possible on our daily driver Chevelle so we went with a 160-degree thermostat. It’s also important to note that the Holley Sniper EFI system does not start self-learning until the water temp reaches 160 degrees.

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12. The distributor easily slides back into place, with the rotor pointing toward the number one cylinder once the distributor is seated.

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13. Now it’s time for the fun stuff! We’re ready to install the Holley Sniper EFI throttle body. We ordered ours with the Classic Gold finish (PN 550-516), and it should look right at home on our stock 283ci engine.

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14. The Sniper EFI throttle body bolts onto a four-barrel intake, using four bolts, or in our case, four studs and nuts.

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15. Our original throttle linkage can be reused, but every car is different. Your application may need some adjustment to have the full range of motion.

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16. The Holley Sniper EFI kit comes with a modern style coolant temperature sensor, which threads into the Weiand intake manifold with a small amount of sealant on the threads. Then, we plug in the connector from the Sniper wiring harness.

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17. Wiring for the Holley Sniper EFI system is self-explanatory, as most of it is a simple plug-and-play connection.

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18. As we routed the wires and the fuel hoses (supply and return), we found a nice home for the fuel pump relay. This clamp holds the fuel hoses and the relay, and it mounts to the heater box stud for easy access.

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19. Our Chevelle doesn’t have many accessories so we were able to run the 12v power wire to an open terminal on the fuse block. The important thing is that the terminal provides a constant 12 volts with the key in the On position.

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20. The Holley Sniper EFI kit features a small yellow wire that connects to the negative side of the ignition coil. We shortened the wire and installed a ring connector before installing it on the coil.

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21. The final step for wiring is to install the main hot wire and ground directly to the battery. This works best if you have a battery with top and side posts. The only remaining wire in the system is the blue wire, which powers the electric fuel pump.

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22. The Sniper EFI throttle body has three options for the fuel supply line and we chose the one at the driver-side rear. The fuel return hose connects on the passenger side at the rear of the unit, where the built-in fuel pressure regulator is located. We used Earl’s 3/8-inch fuel-injection hose and clamps.

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23. There are a couple of options for fuel delivery. One is to install an inline fuel pump outside of the tank and the other is to install a new EFI-ready fuel tank. We opted for the new Sniper EFI-ready Fuel Tank (PN 19-105), as this allowed us to use the supplied in-tank Walbro 255-lph fuel pump.

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24. We covered the complete installation of the Holley EFI-ready fuel tank and pump system in a previous article. After fitting the fuel pump and sending unit assemblies to the new tank, we connect the blue fuel pump power wire, the grounds, and the fuel hoses.

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25. Since we’re swapping to an electric fuel pump, we need to block off the original mechanical fuel pump hole. Holley includes this finned plate in its Sniper EFI kit.

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26. Finally, we needed to install a bung for the O2 sensor. There isn’t a precise, preferred angle but as long as the O2 sensor is at least 90-degrees in relation to the ground, it will keep it from showing a false reading due to collecting condensation or raw fuel.

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27. Now we can finally put power to the system by hooking up the battery, and turning the ignition switch to the On position. The Holley Sniper EFI handheld display quickly loads and starts a series of options to select. First is the system type, which includes the part number of our Sniper EFI kit.

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28. From there, the display gives you the option for number of cylinders, which is obviously eight for this application.

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29. Holley’s system features a sliding scale for the cubic inches. We move the bar to 283 cubic inches and click Next.

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30. Next is the target idle speed, which we set for 850 rpm. This is something that we can dial in later, as the system tunes itself.

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31. The next option is for the type of camshaft in use. The three options give the Sniper EFI system an idea of your engine’s build type so that it can tune accordingly. Our old 283 is bone stock, so we chose the Stock/Mild option.

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32. Power Adder Type is the next option, which we answer with None. The Sniper EFI system is capable of supporting nitrous oxide, supercharged, and turbocharged combinations.

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33. The final option is the ignition source. For our application, we’re running an old-style small-body distributor with an external coil, so we choose the “Coil (-)” option.

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34. And now for the moment of truth, we turn the key and the car fires within a couple of rotations of the starter. The Holley system has default settings for target air/fuel ratios, which can be changed to your liking. The system begins self-tuning when the coolant temperature reaches 160 degrees (this can also be changed).

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35. We finished off the Sniper EFI install with a set of Holley’s new Vintage Series finned aluminum valve covers in polished finish (PN 241-241). We matched it with a 14-inch round finned aluminum air cleaner (PN 120-151), complete with 3-inch premium element.

Photos by Tommy Lee Byrd


Holley Performance Products
Bowling Green, KY 42101



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