Air Injection Check Valve

Remove and replace the air injection check valve on a 1966 Chevrolet Corvette 327ci V8 to restore proper operation of the air injection smog system.

Warnings

Tools required

Parts

• Air injection check valve × 1 — Use OEM specification
• Air injection hose (if deteriorated) × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and set parking brake
2. Allow engine to cool completely if recently operated
3. Open hood and secure with prop rod
4. Locate the air injection check valve on the passenger side of the engine near the cylinder head
5. Inspect all air injection hoses for cracks or deterioration while access is available

Procedure

1. 1

   Locate and inspect the check valve assembly
   The air injection check valve is located on the passenger side of the engine, typically threaded onto the inlet pipe of the air distribution manifold that feeds air to the exhaust ports, with the air pump output hose connecting to its opposite end. It is a cylindrical metal component approximately 3 inches long with hose connections on both ends. Inspect the valve and surrounding hoses for obvious damage, cracks, or oil contamination.
2. 2

   Disconnect air pump supply hose
   Loosen the hose clamp securing the air pump supply hose to the inlet side of the check valve. The valve body has a directional flow arrow that points toward the distribution manifold; the inlet side is the end facing the air pump supply hose. Use a flathead screwdriver or 5/16" socket to loosen the clamp. Slide the clamp back along the hose and carefully twist and pull the hose off the check valve inlet fitting.
3. 3

   Disconnect distribution manifold hose
   Loosen the hose clamp securing the distribution manifold hose to the outlet side of the check valve. Slide the clamp back along the hose. Twist and pull the hose off the check valve outlet fitting. If the hose is stuck due to age or heat deterioration, apply penetrating oil and allow 5 minutes of soak time before attempting removal.
4. 4

   Remove check valve mounting bracket
   On many 1966 Corvette A.I.R. installations the check valve threads directly into the air distribution manifold rather than mounting to a bracket. If a bracket is present, remove its 2 bolts with a 7/16" socket; otherwise, unthread the check valve from the distribution manifold fitting using a wrench, supporting it to prevent dropping.
5. 5

   Remove old check valve
   Once the mounting bracket is detached, remove the check valve assembly from the engine bay. Inspect the valve body for the directional arrow to confirm proper previous installation. Set the old valve aside for comparison with the replacement part.
6. 6

   Inspect hose fittings and clean mating surfaces
   Examine both hose ends that were connected to the check valve. Look for cracks, hardening, or internal deterioration. If hoses are damaged, replace them now while access is available. Use a wire brush to clean any corrosion or debris from the hose fittings. Wipe clean with a shop rag.
7. 7

   Verify new check valve orientation
   Locate the directional arrow stamped or cast into the body of the new check valve. This arrow must point from the air pump toward the distribution manifold (toward the engine). Incorrect installation will allow exhaust gases to back-feed into the air pump, causing immediate damage.
8. 8

   Install new check valve into mounting bracket
   Position the new check valve into the mounting bracket, ensuring the directional arrow points toward the distribution manifold. Align the bracket with the mounting holes on the engine or inner fender.
9. 9

   Secure mounting bracket
   Install and hand-tighten the 2 mounting bracket bolts. Tighten the bolts in an alternating pattern using a 7/16" socket or wrench until the bracket is firmly secured. Do not overtighten as this can crack the check valve housing.
10. 10

    Connect air pump supply hose
    Slide the air pump supply hose onto the inlet fitting of the new check valve. Ensure the hose is pushed fully onto the fitting until it contacts the valve body. Slide the hose clamp into position approximately 1/4 inch from the end of the hose. Tighten the clamp securely using a flathead screwdriver or 5/16" socket.
11. 11

    Connect distribution manifold hose
    Slide the distribution manifold hose onto the outlet fitting of the new check valve. Ensure the hose is fully seated on the fitting. Position the hose clamp approximately 1/4 inch from the hose end and tighten securely. Verify both hose connections are tight and properly clamped.

Reassembly

1. Double-check that the check valve directional arrow points from air pump toward distribution manifold
2. Verify all hose clamps are tight and properly positioned
3. Ensure the mounting bracket is secure with no excessive movement of the check valve

Verification

• Start the engine and listen for unusual hissing, popping, or backfiring from the exhaust or air injection system
• With engine at idle, check all hose connections for air leaks by feeling for escaping air
• Rev the engine to 2000 RPM briefly and verify no backfiring occurs during deceleration
• Inspect the check valve and connections after 5 minutes of operation for any signs of exhaust gas leakage (soot or discoloration)
• Verify the air pump operates normally without unusual noise or vibration

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