The Holley 7-Inch 12-1X Modular Crank Trigger Kit supplies an accurate engine speed and position signal to most EFI systems and ignition controllers (ECU not included). Designed for early Small Block Chevy applications running an aftermarket ATI Super Damper or Fluidampr-style harmonic balancer, the 7-inch trigger wheel centers off the balancer hub, so no separate centering ring is needed.
Specifications:
- Diameter: 7-inch
- Engine Application: Small Block Chevrolet
- Sensor Type: Hall Effect (3-wire, screw-in)
- Color: Silver
- Contents: Bracket, mounting hardware, and Hall-Effect sensor
- Part Number: 556-171
Requires a balancer with a center-hub extrusion and a 3-hole wheel mounting bolt pattern — it will not fit balancers without a center-hub (such as Innovators West units). Some vehicles may need slight modification to accommodate engine plates or pulley systems.
Compliance: This part is legal for sale and use on Racing Use Only Vehicles — competition vehicles that are not registered and never operated on the street. It is against the law to install this part on an Emissions Controlled Vehicle (1966-and-newer California-certified or 1968-and-newer federally certified vehicles).
FAQ
What balancer does this kit require?
An aftermarket ATI Super Damper or Fluidampr-style balancer with a center-hub extrusion and a 3-hole wheel mounting bolt pattern. It will not work on balancers without a center-hub, such as Innovators West units.
What's included in the kit?
The 7-inch trigger wheel, mounting bracket, hardware, and a screw-in 3-wire Hall-Effect sensor.
Does this kit include an ECU?
No. It provides the crankshaft speed/position signal only; control is enabled by a separate ECU.
Is this part legal for street use?
No. It is legal for Racing Use Only vehicles and cannot be installed on an emissions-controlled street vehicle.
