Installing Holley’s Sniper EFI Quadrajet System on a 1970 Corvette
Inject-a-Vette
HOT ROD StaffWriter
Fuel delivery technology has come a long way in the past few decades. Yesterday's carburetors can't hold a candle to modern EFI systems in terms of driveability, economy and reliability. Changing weather conditions and modern fuels can still cause the best-running carburetor to stumble or leave you stranded. If you really like driving your Corvette but wish it had better manners, the best solution is to invest in a modern fuel-injection system.
For many owners, installing a complex EFI system and maintaining originality is an oxymoron. Well, Holley believes that simplicity and originality are also important when converting to EFI. Holley leverages its "keep it simple" philosophy with their Sniper EFI systems.
Their hot-selling Sniper throttle-body injection systems have replaced thousands of carburetors across the world, but until now, those looking to replace their Quadrajet carburetors were out of luck without a manifold change. Owners of Quadrajet-equipped vehicles can now enjoy the benefits of a Holley Sniper EFI system without sealing plates, adapters, or swapping intake manifolds.
The Holley Sniper EFI Quadrajet is a self-contained throttle-body injection system that's a direct replacement for spreadbore Quadrajet carburetors found on many classic GM vehicles. To simplify installation, the Sniper throttle body contains the EFI computer, air temperature sensor, idle control and fuel injectors.
Owners also don't need a PhD in computer science to tweak the Sniper EFI system. Got some fingers and a right foot? That's all you need to tune the Holley Sniper EFI Quadrajet. After selecting a few options on the included handheld touch screen, the Sniper EFI Quadrajet system adjusts itself while you drive. The included Bosch wide-band oxygen sensor and smart self-tuning strategy do all the hard work while you simply enjoy your car.
Though Holley went to great lengths to simplify the Sniper EFI Quadrajet system, they didn't skimp on powerful features. When installed with Holley's HyperSpark distributor, the Sniper has full control over the ignition timing for even better power, economy and driveability.
EFI systems require a much higher fuel pressure, so Holley offers a wide range of fuel system options; from simple, in-line fuel pumps to EFI-ready replacement fuel tanks.
We've heard a lot of good things about Holley's Sniper EFI throttle-body systems. To see what all the fuss was about we followed along as Holley technicians converted a 1970 Corvette to Sniper EFI. Though it would've been simpler to use an in-line, external fuel pump, Holley went a different route. Because the factory fuel system had seen better days, they decided to replace the fuel tank with one of Holley's EFI conversion tanks. The tank includes a drop-in, in-tank pump and fuel level sender for quiet operation and modern convenience.
The 1970 Corvette still had the original ignition system, so using the Holley Sniper EFI HyperSpark distributor eliminated the troublesome break point distributor and gave full ignition timing control to the Sniper EFI Quadrajet. Vette
Besides the Holley Sniper EFI Quadrajet system, Holley opted to replace the original factory fuel tank with one of Holley's EFI conversion fuel tanks. They also used one of Holley's HyperSpark ignition distributors to replace the factory points distributor, which gives the Sniper EFI system full control over the ignition timing.
We began by removing the factory Quadrajet carburetor from the intake manifold.
The Holley Sniper EFI Quadrajet throttle body (right) matches the spreadbore pattern of the factory Quadrajet carburetor (left).
To simplify installation, the Sniper throttle body contains the EFI computer, air temperature sensor, idle control and fuel injectors. Only four wiring connections are required (power, ground, switched ignition and rpm signal), greatly simplifying installation.
Because this Corvette still had the factory points ignition system (and they wanted to control ignition timing with the Sniper), Holley chose their Sniper EFI HyperSpark distributor (PN 565-300) along with a HyperSpark Coil (PN 556-152) and Sniper EFI Coil Driver Module (PN 556-150).
To keep things simple, they chose Holley's Sniper EFI Coil Driver Module, (left), but for higher performance applications Holley offers a capacitive discharge ignition amplifier (PN 556-151).
After removing the spark plugs and wires, we removed the original points distributor.
Next to go was the factory mechanical fuel pump, which was replaced with a block-off plate.
Next, we removed the factory fuel tank. From the smell of it, the gasoline inside might've been original.
Holley offers this cool Sniper EFI Fuel Tank System, (PN 19-148) that includes a 255-lph fuel pump and fuel sending unit compatible with a factory-style fuel gauge sending unit.
We ran the fuel pump power wire from the Sniper EFI harness back to the tank and found a good ground on the frame for the pump.
We extended the wire for the fuel level sender, which is relocated to the top of the Sniper EFI conversion fuel tank.
To supply the Sniper EFI Quadrajet system with clean fuel at the right pressure, we chose a popular LS-style GM fuel filter regulator and used Earl's fittings (PN 961965ERL and AT991966ERL) to connect to -6 Earl's Vapor Guard hose and fittings.
We mounted the fuel filter regulator to the back bumper bracket.
We used Earl's Vapor Guard hose to connect to the factory hard line, and used some rubber hose for the tank vent.
With the pump and sender installed in the tank, we used Earl's Vapor Guard hose and fittings for the pump's feed and return connections.
Next, we lifted the tank into position and used the included tank straps to keep it in place.
Moving up front, the old coolant temp sensor was replaced with a new sensor (included with the Sniper EFI kit) that will allow the system to adjust its operation based upon engine temperature.
After finding a suitable location for the included wide-band oxygen sensor, we used a step drill at a downward angle to make the required hole in the exhaust pipe.
Holley includes this handy clamp-on oxygen sensor bung if you don't have access to a welder. It's a great solution (either temporarily or permanently).
After rotating the engine to top dead center on cylinder No. 1, we installed the Holley HyperSpark distributor.
The included alignment cap takes the guesswork out of syncing the distributor pickup with the distributor cap terminal for cylinder No. 1. Going forward, ignition timing adjustments will be controlled exclusively by the Sniper EFI.
Rather than mount the HyperSpark Coil remotely, we installed an MSD Blaster can-style coil that fit the factory coil bracket.
After finding a suitable location for the included wide-band oxygen sensor, we used a step drill at a downward angle to make the required hole in the exhaust pipe.
Next, we finished the battery, ground and remaining wiring connections and bolted the Holley Sniper EFI Quadrajet throttle body to the factory intake manifold.
Even the factory throttle linkage hooked right up to the Holley Sniper EFI Quadrajet throttle lever.
We ran a length of Earl's Vapor Guard hose from the factory hard line to the inlet on the Holley Sniper EFI Quadrajet throttle body, and used an Earl's -AN fitting to make the connection.
With the pump and sender installed in the tank, we used Earl's Vapor Guard hose and fittings for the pump's feed and return connections.
Heck, even the factory air cleaner and chrome ignition shielding fit perfectly. With the Sniper system fully installed the engine compartment looks completely stock, and all of the modifications we made are completely reversible!
With everything hooked up, we followed the setup wizard on the hand-held Sniper EFI touch screen before firing the engine.
We were impressed how the engine started right up and idled smoothly. We drove the Corvette moderately for a few miles so the Sniper EFI Quadrajet system could dial itself in before romping on the gas.
Photography by Wes Duenkel
Source:
Holley Performance Products
(866) 464-6553