Sniper EFI Installation Guide & What's Involved

10 min read

Sniper EFI Installation Guide & What's Involved

10 min read

So you're ready to switch from carburetor to fuel injection, but you're unsure of what all is involved. This guide will walk you through a basic installation including what parts are necessary to swap as well as what to watch out for. It's time to move towards better fuel economy, increased performance and perfect cold starts. Let's get started!

Which Sniper is for Me?

Let's begin with the most crucial factor; will it fit? Manufacturers have used a variety of bolt patterns and it can be difficult determining which one you have. That's why we have this handy bolt pattern guide with printable templates to measure your intake. Sniper EFI currently offers the following bolt pattern options:
ModelBolt PatternSupported HP (N/A Unless Otherwise Noted)# of Injectors
BBD3.25" X 1.87"350HPTwo 100lb/hr
2GC Small Bore3.25" X 1.87"350HPTwo 100lb/hr
2GC Large Bore3.685" X 2.00"350HPTwo 100lb/hr
2300 2-BBL 5.16" X 3.46"350HPTwo 100lb/hr
Super 2300 2-BBL5.16" X 3.46"350HP (N/A) - 650HP (Forced Induction)Four 100lb/hr
Quadrajet4.25" X 5.62" (Spreadbore)500HPFour 100lb/hr
4150Dual (Spreadbore & Squarebore)650HPFour 100lb/hr
Super 4150 650 Dual (Spreadbore & Squarebore)650HPFour 100lb/hr
Super 4150 1250Dual (Spreadbore & Squarebore)650HP (N/A) - 1250HP (Forced Induction)Eight 100lb/hr
4150 2 X 4Dual (Spreadbore & Squarebore)1250HPEight 100lb/hr
Super 4150 2 X 4Dual (Spreadbore & Squarebore)1250HP (N/A & Forced Induction)Eight 100lb/hr
Sniper X-FlowDual (Spreadbore & Squarebore)800HPFour 120lb/hr
Sniper X-Flow 1375Dual (Spreadbore & Squarebore)800HP (N/A) - 1375HP (Forced Induction) Eight 120lb/hr
Stealth 41505.16" X 5.62" (Squarebore)650HPFour 100lb/hr
Super Stealth 4150 6505.16" X 5.62" (Squarebore)650HPFour 100lb/hr
Super Stealth 4150 12505.16" X 5.62" (Squarebore)650HP (N/A) - 1250HP (Forced Induction)Eight 100lb/hr
Stealth 45005.38" X 5.38" (Dominator)1500HP (N/A) - 1250HP (Forced Induction)Eight 100lb/hr

Fuel System Requirements

Okay, great! We've found a Sniper TBI system that will bolt onto your existing intake, but what else is required? For starters, your fuel system will need to be upgraded. Holley carburetors operate at a range of 5.5 to 7.5 psi of fuel pressure and use a 40 micron filter. Sniper EFI throttle bodies require 58-60 psi of fuel pressure and a 10 micron filter. Let's take a look at the items that would need to changed or can handle the higher pressure.

Fuel Pump: On average, your block mounted mechanical pump will produce up to 10 psi of pressure. While it can move the required volume of fuel, it cannot maintain a pressure needed to supply your Sniper's fuel injectors. Alright, but what electric fuel pump should I use? We have three options when it comes to high pressure pumps:

  1. Electric In-Line- Included with most Sniper EFI masker kits, these pumps will be mounted in-line within two (2) feet of the fuel tank and below the lowest point of your tank (gravity feed). Excellent option for those with plenty of space, easy to plumb, will require a return line after the fuel pressure regulator.
  2. Electric In-Tank- Often referred to as "pump on a stick", these fuel pumps will either replace your existing sending unit or require cutting a hole and mounting into your existing fuel tank. Excellent choice for owners with cramped space and those who would like to tone down fuel pump noise. Do not require a return line or external regulator.
  3. Replacement Fuel Tank- Sniper EFI now offers bolt-in fuel tanks for most popular applications, these require assembly but include new straps, fuel pump and sending unit. Perfect for owners working on a project that requires a new tank. Return line after the fuel pressure regulator necessary.

Fuel Line: Unfortunately that 5/16" rubber line with a rusty hose clamp will not live up to the pressure requirements of your new electric pump. For all standard applications, it is recommended to use a 3/8" fuel injection approved hose for your supply and return plumbing. In lower horsepower applications a 5/16" supply line can be utilized but it is vital to take multiple pressure readings to ensure consistency. Our Sniper EFI Master Kits are supplied with 20 feet of EFI compatible rubber hose.

Fuel Filters: Most carbureted applications will require a 100 micron pre-filter (before fuel pump) and a 40 micron post-filter (after pump, before carb). A Sniper EFI system requires the use of 100 micron pre-filter and 10 micron post-filter. It is critical to use high pressure clamps or AN fittings to reduce the possibility of a fuel leak.

Fuel Pressure Regulator: The majority of Sniper EFI systems come with a pre-installed fuel pressure regulator that will work great for all naturally aspirated, nitrous and roots supercharged applications. Blow-through applications will require the use of an external boost referenced regulator (example: 12-848). Below is a list of systems that will require an external fuel press regulator :

  • Sniper EFI Stealth 4150
  • Sniper EFI Stealth 4500
  • Sniper EFI Quadrajet
  • Sniper EFI 4150 2X4
  • Sniper EFI X-Flow

Fuel Fittings: All Sniper EFI systems will use -6AN fuel inlet/outlet connections (Stealth 4500 utilizes -8AN O-Ring Fittings). NOTE: Higher horsepower applications will require installing an -8AN O-Ring fitting (3/4-16 Male O-Ring) to provide sufficient fuel supply.

Ignition Requirements

Spark! No gas engine will run without it, so let's take a peak at what the Sniper EFI requires. All systems are compatible with traditional single coil, even fire 4, 6 and 8 cylinder engines. Timing control is NOT required for the system to function, but it is recommended for optimum performance. Five ignition options are supported: CD Box, Coil (-), Magnetic Pickup Distributors, Holley Dual Sync Distributors and Sniper EFI Hyperspark Distributors. Each ignition option will require a unique configuration, see below for details.

CD Box (Non-Timing Control)

Coil (-) (Non-Timing Control)

Magnetic Pickup

Dual Sync


Wiring Overview

Here we find our overall wiring schematic, detailed explanations for connectors are found in the tables below. Below is a run down of other notable connections: Main Power & Ground - The main power and ground MUST GO TO THE BATTERY. This will be allowing the battery to act as a dampener in the event of a voltage spike from an old radio install or fuse shorting out. DO NOT make these connections until ALL OTHER WIRING HAS BEEN PERFORMED. Switched +12V (Pink Loose Wire) - Must go to a source with the following requirements: Key On, Engine Off = 11.5+ ≥; Key On, Engine Crank = 10+ ≥. Your handheld display must stay powered during cranking for the system to start and function properly. THIS MUST NOT BE CONNECTED TO THE IGNITION COIL OR OTHER "DIRTY" SOURCE! 3.5" Touch Screen LCD Display - Utilizes a small four-pin CAN connector, to disconnect, depress the locking tab on the male side of the connector. Coolant Temperature Connector - Connects directly to the two pin coolant temperature sensor, the replacement sensor part number is 543-120. Oxygen Sensor Connector - Connects directly to the oxygen sensor, the replacement sensor part number is 554-155. PLEASE ROUTE AWAY FROM HEAT SOURCES SUCH AS EXHAUST MANIFOLDS. Fuel Pump Output (Blue Loose Wire) - Will connect directly to the positive terminal on electric fuel pump. Fuel pump draw may not exceed 15A, if this is the case, wire a larger fuel pump relay in-line.

7 Pin Connector (Main Sniper Harness)

PinColorLabeled NameFunction
ERedBattery Positive (+)Connects directly to battery positive terminal - CONNECT LAST
GBlackBattery Negative (-)Connects directly to battery negative terminal - CONNECT LAST
CBlueFuel Pump Output (+)+12v Fuel Pump Supply from Relay
Crank Signal Positive (+)Engine Speed Signal Input
BDark GreenCrank Signal Negative (-)Engine Speed Signal Ground
DYellowCoil (-) InputEngine Speed Input (ONLY FOR USE WITH COIL (-) IGNITION SETUP)

10 Pin Connector (Sniper EFI I/O Harness)

PinColorLabeled NameFunction
AOrangeInput #1 (-)Optional - A/C Relay
BYellowInput #2 (-)Optional
CLight BlueOutput #1 (-)Optional - Fan #1
DLight GreenOutput #2 (-)Optional - Fan #2
EGreyOutput #6 (-)Optional - A/C Shutdown
FWhitePoints OutputTrigger CD Box or Coil Driver Module
GDark BrownTach OutputOptional - Connect to aftermarket tachometer
HTanDigital Gauge OutputOptional - Connect to Holley EFI Analog Gauges (using 554-130 Module)


PinColorLabeled NameFunction
AOrangeSensor Reference (+5V)Optional - +5V supply for 0-5V sensor
BBlackSensor Ground (-)Optional - Ground for 0-5V sensor
CVioletInput #3 (+5V)Optional - Used for programmable 0-5V sensor input
DPinkInput #4 (+5V)Optional - Used for programmable 0-5V sensor input
EDark GreenInput #5 (+5V)Optional - Used for programmable 0-5V sensor input
FDark BlueOutput #3 (-)Optional - Used for programmable ground output
GDark BrownOutput #4 (-)Optional - Used for programmable ground output
HGreyOutput #5 (-)Optional - Used for programmable ground output

Hopefully, this guide will resolve some questions you may have considered when installing a Sniper EFI system. Fuel injection can be daunting after a life of tuning carburetors, but Sniper EFI is arguably one of the simplest to install systems available on the market. Be sure to check out the full instruction manual filled with tons of information regarding installation, tuning and more! 


Staff Writer
1716 Posts