Holley HP EFI Stealth Ram MPFI Fuel Injection System Chevy V8

Holley HP EFI Stealth Ram MPFI Fuel Injection System Chevy V8 550-820 - Small Block Chevy, Early to Late Heads, Range Up To 500 HP 550-823 - Small Bloc
HolleyHolley HP EFI Stealth Ram MPFI Fuel Injection Syst

Holley HP EFI Stealth Ram MPFI Fuel Injection System Chevy V8

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Holley HP EFI Stealth Ram MPFI Fuel Injection System Chevy V8

550-820 - Small Block Chevy, Early to Late Heads, Range Up To 500 HP
550-823 - Small Block Chevy, Early to Late Heads, Polished, Range Up To 500 HP
550-825 - Small Block Chevy, Vortec Heads, Range Up To 500 HP
550-828 - Small Block Chevy, Vortec Heads, Polished, Range Up To 500 HP

You'll get some attention when you pop the hood and show an HP Stealth Ram Multi-Point EFI system! Available for traditional or Vortec headed SB Chevys. Simply utilize a laptop (or the optional 5.7" full color touch screen LCD) along with the HP's self-tuning capabilities to make it easy as 1, 2, 3 to get your car up and running with EFI. The tunnel ram design of the Stealth Ram builds power in the upper RPM while maintaining excellent mid-range torque as well. HP Stealth Ram systems include: intake manifold, billet throttle body, ECU, wiring harness, fuel rails and related small parts. Fuel pump and Injectors should be selected separately to fit your requirements.

Installation Notes:
ECU is certified to ISO 8846, SAE J1171 & United States Coast Guard Requirements for Ignition Protection & Fire Resistance.

Holley HP EFI systems are equipped with 4 programmable inputs and 4 programmable outputs that are ideal for most vehicles with a single power adder. This feature allows the user to configure the system to support a wide range of controls including boost control, progressive nitrous, water/meth injection, speed inputs, fuel pump control, AC inputs, timing retard inputs and various other uses. When selecting an ECU, users need to ensure their planned controls can be run with the 4 inputs and 4 outputs as certain combinations may use more I/Os than are available. If more I/Os are required, users should choose the Dominator VMS.


  • Optional 5.7" full-color touchscreen LCD allows easy on-the-fly tuning, data-logging or can be used as an easy to see graphical gauge panel
  • Eight sequentially driven 8:2 peak and hold injector drivers, capable of driving up to 16 low or high impedance injectors as a standard feature. Multiple staged injector strategies
  • Eight channel Distributorless Ignition (DIS) outputs capable of directly driving "Smart" ignition coils or Holley DIS coils. Will drive 2 wire coils with the addition of PN 554-112 high current coil driver module
  • Plug and Play control of factory GM 24x and 58x LSx engines
  • Integrated single channel wide band oxygen sensor control. Works with NTK or Bosch sensors. More channels can be added via CAN bus
  • Internal data-logging standard with a huge 2GB of memory
  • 4 Stage progressive nitrous control
  • Turbo boost control
  • Integrated water/methanol injection control
  • Self-tuning fuel table strategy greatly simplifies tuning process
  • Individual cylinder fuel and spark control allows you to unlock your engine’s potential
  • Works with 4, 6, 8 cylinder engines
  • Unique lb/hr based fueling strategy greatly simplifies and commonizes tuning
  • Advanced idle, closed loop, and enrichment strategies allow for very stable operation
  • ECU is fully potted and can be mounted in the engine compartment or interior
  • Sealed automotive and marine grade connectors
  • Allows for use of common OEM sensors as well as customer sensor calibration input
  • Ignition Plug and Play with GM 24x and 58x LSx engines, GM HEI, Ford TFI, magnetic and hall effect trigger, and other ignition systems. New Plug and Play applications in process. Custom settings can be configured to allow many other applications
  • 1-5 Bar MAP sensor capability
  • Two channel knock control sensor Inputs for both one or two wire knock sensors
  • Dedicated fuel and oil pressure inputs
  • Controls both stepper and PWM Idle Air Control (IAC) motors
  • Speed density, Alpha-N, or combination fueling strategies
  • 4 Programmable high or low Pulse Width Modulated (PWM) outputs and 4 fully configurable inputs can be configured for use
  • 4 Stage nitrous oxide control
  • Fully featured nitrous control eliminates the need for a separate nitrous controller device
  • Can be configured "Wet" or "Dry" with closed loop feedback
  • Progressive control based on time, RPM, or boost, requires part # 554-111
  • Lean or rich safety cutoff
  • Full timing retard/control configurability per stage based on RPM or time
  • Integrated Water/Methanol injection control
  • Uses Holley Water/Meth solenoids specially designed and calibrated for use with this EFI system to allow the user to enter Water/Meth flow as a percentage of fuel injector flow for Water/Meth

Selection Guide: This is good guide we pulled from the Holley site to help you select the right parts to get you started. Most parts can be swapted out for other manufactures. Item highlited in green are already in the 550-603 kit. Items in red are not applicable to either the 550-603 kit or to the HP ECU.

Step 1 (required)
The Dominator EFI ECU Requires a Main Power harness P/N: 558-308
Step 2 (required)

Choose Your Main Harness:
558-100 4BBL TBI Main Harness Only
558-101 TPI/SR Harness
558-102 LS1 Harness
558-103 LS2 Harness
558-104 Universal MPFI
558-105 Unterminated Harness
558-100 Designed for Holley 4 bbl TBI systems
558-102 Designed for 24x crank and 1x rear mount cam sensor. Connects to factory coil harnesses and all factory sensors. Does not require a ignition harness
558-103 Designed for 58x crank and 4x front mount cam sensor. Connects to factory coil harnesses and all factory sensors.
558-104 Fully terminated. Designed for single plane style EFI intake manifolds and Holley MPFI intakes
558-105 15' harness length. Fully terminated and populated at ECU connections only. User must terminate all sensor ends. Includes a variety of sensor connectors and pins but end user may have to supply sensor pins and connectors suited for their specific application
Step 3 (required)
Choose Your Injector Harness
558-200 V8 Injector harness for Chevrolet firing order
558-201 LSx Inj Harness
558-202 Universal 4 Cyl Inj Harness
558-203 Universal 6 Cyl Inj Harness
558-204 Universal Unterminated Inj
558-205 4 Bbl Holley TBI
558-206 Terminated 2x4 Holley TBI
558-207 Unterminated 16 injector MPFI
558-208 Unterminated 24 injector MPFI

558-209 V8 Injector harness for Ford firing order
558-200/558-203 Universal "Y" style harness using standard Bosch style injector connectors
558-201 "Y" style harness for any V8 engine using "EV6" style of injector.
558-202 Fully terminated 4 cylinder harness using standard Bosch style injector connectors
558-204/558-207/558-208 Terminated at injector connectors (Bosch style). Harness must be assembled and require crimping Metripak 150 connectors. Includes all connectors, pins, terminals, and loom needed.
558-206 Fully terminated harness when using two 4Bbl Holley TBI units On LS based engines, the LSX harness should be used on LS2/LS7 engines. It utilizes the EV6 connector. The V8 Injector harness should be used on LS1/LS6 engines. It utilizes the Bosch style connector. Truck engines may have three different connectors. The EV6, Bosch and a GM Multec 2. Currently we do not have a harness for the Multec 2. If injectors have been swaped or are unsure of what you have, it is best to call Holley Tech to determine the correct harness.
Step 4 (required)
Choose your Ignition Harness
558-303 Mag Pickup Ign Harness
558-304 HEI Ign Harness
558-305 Ford TFI Ign Harness
558-306 Universal Unterm Ign Harness
558-307 LS coil retro-fit harness (includes wiring & pins to wire GM LSX coils to non LSX engines. Must supply factory GM coil harness)
558-410 Crank/Cam Ign Harness
558-303 Used to connect to a magnetic pickup distributor or crank trigger. You must supply sensor connectors / pins.
558-304 Connects to small cap computer controlled GM HEI
558-306 Semi-terminated. Includes all wiring to hook up to any crank and cam sensor. Shield/ground cable used. You must supply crank/cam pins and connectors for their specific sensor and may have to crimp metripak 150 pins.
558-410 Fully terminated harness. Connects to Holley 60-2 crank sensor and GM Cam-Sync Distributor AC Delco PN 213-350 or eficonnection.com sync pulse distributor.
Step 5 (optional)
Choose Your Transmission Control
558-405 4L60/80 Harness
Transmission control with Dominator ECU ONLY 558-405 - Fully terminated harness for GM 4L60/65/70/80/55E transmissions
Step 6 (optional)
Choose Your Drive-By-Wire Control
558-406 GM DBW Harness
DBW control with Dominator ECU only! Only works with the following throttle bodies and DBW pedal assembly Approved GM throttle body part numbers:
GM P/N 12570790
GM P/N 12580760
Approved GM Throttle Pedal Assy part number:

GM P/N 10379038
Step 7 (optional)
Choose your Auxillary Harness
558-400 J1A/B I/O Cnctr. Dom & HP
558-401 J2A Cnctr. & Harness
558-402 J2B Cnctr. & Harness
558-403 J3 Cnctr. & Harness
558-404 J4 Cnctr. & Harness
558-408 J2-J4 Cnctr. Kit
558-400 Connects into Main Harness Input/Output Connector (8 pin metripak). Loose lead wires.
558-401 Includes J2A ECU connector with fully terminated #2 wide band oxygen sensor cabling. Comes with loose lead wires for all other input connections (qty 23). ECU pins are pre-crimped.
558-402 Includes J2B ECU connector. Includes all output connection wires (qty 16). ECU pins are pre-crimped.
558-403 Includes J3 ECU connector. Includes all input and output connection wires (qty 17). ECU pins are pre-crimped.
558-404 Includes J4 ECU connector. Includes all input and output connection wires (qty 26). ECU pins are pre-crimped.
See holleyefi.com for more info.
Step 8 (optional)
Choose Your Injectors
522-191 Single Inj 19PPH
522-198 8 pk Inj 19PPH 300HP Max
522-241 Single Inj 24PPH
522-248 8 pk Inj 24PPH 385 HP Max
522-301 Single Inj 30PPH
522-308 8 pk Inj 30PPH 480 HP Max
522-361 Single Inj 36PPH
522-368 8 pk Inj 36PPH 575 HP Max
522-421 Single Inj 42PPH
522-428 8 pk Inj 42PPH 670 HP Max
522-481 Single Inj 48PPH
522-488 8 pk Inj 48PPH 765 HP Max
522-661 Single Inj 66PPH
522-668 8 pk Inj 66PPH 1050 HP Max
522-831 Single Inj 83PPH
522-838 8 pk Inj 83PPH 1325 HP Max
522-121 Single Inj 120PPH
522-128 8 pk Inj 120PPH 1900 HP Max
Step 9 (required)
Choose Your Sensors
554-100 NTK Wideband Sensor
554-101 Bosch Wideband Sensor
554-102 100 PSI Sensor
554-103 200 PSI Sensor
554-104 1600 PSI Sensor
538-24 1 bar MAP sensor
538-13 2 bar MAP sensor
554-107 3 bar MAP sensor
554-108 5 bar MAP sensor
534-10 Coolant Temp Sensor
9920-107 Air Temp Sensor
554-102/554-103/554-104 - Come with short pigtail connector for sensor

Oxygen sensor recommendation:
The NTK sensor is recommended when using leaded or methanol fuels, high exhaust gas temperature applications (turbo charged) or for highest precision feedback.
Step 10 (optional)
Choose Your Fuel Pump
12-927 In-Line pump (TBI Units)
12-920 In-Line pump (Multi Port Units)
12-927 flows 258 pph at 15psi.
12-920 flows 402 pph at 45psi.
Many More Pump Available (Here)
Step 11 (optional)
Choose your Crank Trigger System
556-110 SBC Crank Trigger Kit
556-111 BBC Crank Trigger Kit
556-110/556-111 - Include everything needed to install a 60-2 crank trigger wheel system on a Small or Big Block Chevy engine for use with an HP or Dominator ECU. Includes wheel, sensor, billet aluminum mounting components, and fully terminated wiring harness with crank and cam sensor connectors. Intended to provide a very accurate RPM signal to the ECU.
Step 12 (optional)
Choose your Distributorless Ignition Systems (DIS)
556-100 4 Cyl DIS System
556-105 6 Cyl DIS System
556-101 8 Cyl DIS System
556-102 SB Crank Sensor mounting kit
556-103 BB Crank Sensor mounting kit
556-104 Coil
556-106 5" Crank trigger wheel
556-107 6" Crank trigger wheel
556-108 7 3/4" Crank trigger wheel
556-109 8 1/2" Crank trigger wheel
The installation of Holley DIS on Small and Big Block Chevy engines requires the purchase of PN 556-101 and either the 556-102 or 556-103
566-100/556-101/556-105 - Comes with Coils, Crank/Cam sensor wiring, Coil wiring, and Crank Sensor. Must purchase trigger wheel and mounting kit components in addition.
556-102/556-103 - Complete trigger wheel and sensor mounting kit for SB/BB Chevy engines. Comes with 8-1/2 trigger wheel, and billet aluminum bracketry to mount crank sensor. Can be mounted on either side of block and is fully adjustable. Requires accessories to be moved 1/8" out. Includes 1/8" water pump pulley spacer.
The installation of Holley DIS on non-Small/Big Block Chevy engines requires the purchase of PN 556-100/556-101/556-105 and a properly sized trigger wheel (PN’s 556-106/556-107/556-108/556-109). The user will have to machine the trigger wheel mounting pattern as well as fabricate a rigid mount for the crank sensor itself.

Individual Trigger Wheels:
PN 556-109 - Bolt hole pattern machined for SB/BB Chevy Engines
PN 556-106/556-107/556-108 - Machined only with 1" diameter center hole. Must be machined to mount to specific application.
Step 13 (optional)
Choose Your Modules
554-111 Nitrous solenoid driver
554-112 2 wire coil driver module
554-115 Peak and Hold Module, Water/Meth
554-111 - The nitrous solenoid driver is REQUIRED when progressively controlling nitrous oxide solenoids. It can be used for non-progressive nitrous to replace a standard relay. Requires a PWM - (ground) output
554-112 - Required when using 2 wire coils. One module can drive 4 coils. Dominator and HP ECUs can directly trigger "smart coils" triggered by a 5 volt input.
554-115 - Required to drive a water/methanol solenoid if there is not an extra injector driver available.
Step 14 (optional)
Choose Your Water Meth
557-100 Pump
557-101 Installation kit
557-103 Solenoid/Nozzle 600CC up to 400HP
557-105 Solenoid/Nozzle 900CC up to 600HP
557-106 Solenoid/Nozzle 1000CC up to 800HP
557-107 Water Inj Filter
For a complete kit, a pump, installation kit, filter and solenoid nozzle of the appropriate size is required. A peak and hold module may be required when using an HP ECU.
Step 15 (optional)
Choose Your Boost Control
557-200 3 port valve
557-201 4 port valve
Boost control is not currently available. Check holleyefi.com for updates and availability.
Step 16 (optional)
Choose your Gauges / Displays
553-100 Gauge "Black"
553-101 Gauge "Chrome"
553-103 5.7" LCD Touch Screen
553-104 Avenger Handheld Controller
Gauges can be individually configured to display any sensor that is parameter available in the ECU (RPM, voltage, oil pressure, etc).
553-104 Can be used with the HP and Dominator & allows basic tuning and monitoring functions. Can also be used as a replacement on the Avenger.

Step 17 (optional)
Choose Your Accessories
558-407 Multi Map Selector
558-409 Sealed USB Cable
558-407 Four position key switch that allows the user to select from 4 stored calibrations without the need of a laptop computer. Dominator ECU only.

Application List

ImageSKU / Part NoApplicationStockPriceADD TO CART
HOL550-823Select Cylinder Type and Finish: Early to Late Heads and Polished Finish0$3,295.95Call for Price
HOL550-828Select Cylinder Type and Finish: Early to Late Heads and Polished Finish0$3,295.95Call for Price
HOL550-820Select Cylinder Type and Finish: Early to Late Heads and Satin Finish0$2,942.95Call for Price
HOL550-825Select Cylinder Type and Finish: Vortec Heads and Satin Finish0$2,717.95Call for Price

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