Emissions Inspection

Perform a comprehensive emissions inspection on a 1966 Chevrolet Corvette 327ci V8 to verify compliance with applicable emissions standards and ensure proper operation of emission control systems.

Warnings

Tools required

Preparation

1. Verify vehicle identification and confirm model year 1966 with 327ci V8 engine
2. Ensure engine is at normal operating temperature (190-195°F)
3. Check that all emission control components are present and appear factory-correct for 1966
4. Verify fuel system has no visible leaks
5. Confirm air cleaner assembly is properly installed and sealed

Procedure

1. 1

   Verify PCV System Operation
   Locate the PCV valve in the driver-side valve cover. With engine idling, remove the PCV valve from the valve cover grommet while keeping it connected to the hose. Place your thumb over the valve inlet - you should feel strong vacuum. Shake the valve and listen for the internal rattle indicating the valve is not stuck. Inspect the PCV valve grommet in the valve cover for cracks or deterioration. Check the PCV hose routing from the PCV valve to its vacuum source (carburetor base or intake manifold) for cracks, splits, or disconnection. Note that 1966 327 PCV configurations vary; verify the actual factory routing for this vehicle.
2. 2

   Inspect Crankcase Ventilation System
   Remove the air cleaner assembly. Locate the crankcase breather tube connection at the passenger-side valve cover and verify it connects properly to the air cleaner base. Check that the breather cap filter element (if equipped) is clean and not saturated with oil. Inspect the oil filler cap for proper sealing. Verify no modifications have been made to vent crankcase gases to atmosphere rather than through the closed PCV system.
3. 3

   Check for Evaporative Emissions Controls
   Inspect the fuel system for any evaporative emission control devices. The 1966 Corvette was not equipped with factory evaporative emission controls; EVAP systems did not appear until the 1970-1971 model years. California-spec 1966 vehicles may instead have an Air Injection Reactor (AIR/smog pump) system. Check the fuel tank cap for proper sealing and inspect fuel lines from tank to carburetor for leakage or deterioration. Check the fuel tank cap for proper sealing. Inspect fuel lines from tank to carburetor for any signs of leakage or deterioration that would allow fuel vapors to escape.
4. 4

   Verify Ignition Timing
   Connect timing light to number one cylinder spark plug wire. With engine at curb idle in neutral or park (typically around 600-700 RPM), disconnect and plug the distributor vacuum advance line. Aim timing light at timing marks on harmonic balancer and timing tab. Verify base timing is set to factory specification (typically 4-8 degrees BTDC for 1966 327). Reconnect vacuum advance line and verify timing advances properly with vacuum applied. Incorrect timing directly affects emissions and engine performance.
5. 5

   Check Carburetor Operation and Condition
   With engine at normal operating temperature and idling, observe carburetor for external fuel leaks at bowl gaskets, accelerator pump cover, and fuel inlet. Check throttle linkage for smooth operation with no binding. Verify choke is fully open when engine is warm. Listen for vacuum leaks around carburetor base gasket. Check idle mixture adjustment - exhaust should not be excessively rich (black smoke) or lean (popping/backfiring).
6. 6

   Perform Vacuum System Inspection
   Connect vacuum gauge to intake manifold vacuum port. At idle, vacuum should read 16-20 inches Hg with steady needle. Low or fluctuating vacuum indicates potential intake leaks, valve problems, or ignition issues affecting emissions. Check all vacuum hoses for routing, condition, and proper connection. Inspect distributor vacuum advance canister for leaks by applying vacuum with hand pump if available.
7. 7

   Inspect Exhaust System Integrity
   Visually inspect entire exhaust system from manifolds to tailpipes for leaks, damage, or modification. Check exhaust manifold-to-head connections for evidence of leaks (soot staining). Inspect exhaust pipe connections and hangers. Start engine and check for exhaust leaks by listening and feeling for escaping gases. Any leaks upstream of the tailpipe exit can allow toxic gases into the passenger compartment.
8. 8

   Check Engine Operating Temperature
   Verify engine coolant temperature is within normal range (approximately 180-195°F, consistent with the factory thermostat rating) using dash gauge or infrared thermometer on thermostat housing. Cold-running engines produce excessive emissions due to enriched fuel mixture. Check that thermostat is functioning properly by feeling upper radiator hose for heat after warmup. Inspect radiator cap for proper pressure rating (typically around 13 PSI for this era; verify against factory specification).
9. 9

   Observe Exhaust Smoke and Odor
   With vehicle stationary and adequate ventilation, observe tailpipe emissions. Normal operation should produce minimal visible smoke after warmup. Blue smoke indicates oil consumption (rings, valve guides, or PCV system problems). Black smoke indicates overly rich fuel mixture (carburetor adjustment, choke, or air cleaner restriction). White smoke after warmup indicates coolant consumption. Note any strong fuel odor indicating incomplete combustion.
10. 10

    Perform Road Test Emissions Observation
    If applicable, perform brief road test to verify emissions performance under load. Accelerate moderately and observe for excessive smoke, hesitation, or backfiring. Check for smooth operation at steady cruise speeds. Deceleration should occur without excessive popping or afterfire from the exhaust. These symptoms indicate mixture problems affecting emissions output.

Reassembly

1. Reinstall air cleaner assembly ensuring all connections are secure
2. Reconnect any vacuum lines or hoses that were removed for inspection
3. Verify PCV valve and hose are properly seated and connected
4. Double-check that no tools or parts were left in engine compartment

Verification

• Engine should idle smoothly at 600-700 RPM with no rough running or stalling
• PCV system should show strong vacuum at valve with characteristic rattle when shaken
• Timing should be within specification with proper vacuum advance operation
• Exhaust should be relatively clean with no excessive smoke or strong fuel odor
• Engine should reach and maintain normal operating temperature
• No vacuum leaks or exhaust leaks should be present
• All emission control components should be properly installed and functional

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