This procedure addresses a common misunderstanding: the 1966 Chevrolet Corvette 327 V8 was not equipped with oxygen sensors from the factory, as these were introduced with emissions control systems in the mid-1970s. This guide explains the situation and provides context for owners.

Warnings

Preparation

1. Verify whether your vehicle has been modified with an aftermarket fuel injection or emissions control system
2. If O2 sensors are present, identify the aftermarket system manufacturer and locate installation documentation
3. Confirm the vehicle's original carburetor and ignition system configuration if unmodified

Procedure

1. 1

   Inspect exhaust system for O2 sensor bungs
   Raise the vehicle safely on jack stands or a lift and inspect the exhaust manifolds and exhaust pipes for threaded O2 sensor bungs (typically M18x1.5 threaded ports). Factory 1966 exhaust systems will not have these bungs. If present, they indicate aftermarket modification.
2. 2

   Identify fuel system type
   Confirm whether the engine retains its original carburetor setup (factory Rochester or Holley 4-barrel) or has been converted to throttle body injection, multi-port fuel injection, or another aftermarket system. O2 sensors are only relevant for electronically-controlled fuel injection systems.
3. 3

   Locate aftermarket system documentation
   If an aftermarket fuel injection system is installed (such as Holley Sniper, FiTech, Edelbrock Pro-Flo, or similar), locate the installation manual and wiring diagrams. O2 sensor replacement procedures, connector types, and sensor specifications vary significantly between manufacturers.
4. 4

   Determine O2 sensor type and location
   For aftermarket systems, identify whether the system uses wideband or narrowband O2 sensors, how many sensors are installed (typically 1-2 on V8 conversions), and their exact locations in the exhaust system. Most systems place sensors 6-18 inches downstream of the exhaust manifold collectors.
5. 5

   Follow manufacturer-specific replacement procedure
   Disconnect the battery negative terminal. Allow the exhaust system to cool completely (minimum 2 hours after running). Disconnect the O2 sensor electrical connector according to the aftermarket system's wiring. Use an O2 sensor socket (typically 22mm or 7/8 inch with wire clearance slot) to remove the sensor by turning counterclockwise. Apply anti-seize compound to the threads of the new sensor (avoid contaminating the sensor tip) and install hand-tight, then tighten according to the aftermarket manufacturer's specifications (typically 28-33 lb-ft, but verify with your system's documentation).

Reassembly

1. Reconnect O2 sensor electrical connector(s) ensuring weather seals are properly seated
2. Secure any wiring with factory-style clips or heat-resistant tie wraps away from exhaust heat and moving components
3. Reconnect battery negative terminal and clear any diagnostic trouble codes using the aftermarket system's procedure

Verification

• Start the engine and verify the aftermarket ECU recognizes the new O2 sensor (check display or data logging function)
• Allow the engine to reach operating temperature and confirm the O2 sensor reaches closed-loop operation (sensor actively switching voltage)
• Check for exhaust leaks around the O2 sensor bung while the engine is running
• For unmodified vehicles: verify no O2 sensors are present and the carburetor system is functioning as designed

More procedures for this vehicle